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Background: In most cases, lateral patellar dislocation (LPD) is accompanied by chondral injury and may initiate gradual degeneration of patellar cartilage, which might be detected with a T2 mapping, a well‐established method for cartilage lesions assessment. Purpose: To examine short‐term consequences of single first‐time LPD in teenagers by T2 mapping of the patellar‐cartilage state. Study Type: Prospective. Population: 95 patients (mean age: 15.1 ± 2.3; male/female: 46/49) with first‐time, complete, traumatic LPD and 51 healthy controls (mean age: 14.7 ± 2.2, male/female: 29/22). Field Strength/Sequence: 3.0 T; axial T2 mapping acquired using a 2D turbo spin‐echo sequence. Assessment: MRI examination was conducted 2–4 months after first LPD. T2 values were calculated in manually segmented cartilage area via averaging over three middle level slices in six cartilage regions: deep, intermediate, superficial layers, and medial lateral parts. Statistical Tests: ANOVA analysis with Tukey's multiple comparison test, one‐vs.‐rest logistic regression analysis. The threshold of significance was set at P < 0.05. Results: In lateral patellar cartilage, a significant increase in T2 values was found in deep and intermediate layers in both patient groups with mild (deep: 34.7 vs. 31.3 msec, intermediate: 38.7 vs. 34.6 msec, effect size = 0.55) and severe (34.8 vs. 31.3 msec, 39.1 vs. 34.6 msec, 0.55) LPD consequences as compared to controls. In the medial facet, only severe cartilage damage showed significant prolongation of T2 times in the deep layer (34.3 vs. 30.7 msec, 0.55). No significant changes in T2 values were found in the lateral superficial layer (P = 0.99), whereas mild chondromalacia resulted in a significant decrease of T2 in the medial superficial layer (41.0 vs. 43.8 msec, 0.55). Data Conclusion: The study revealed substantial difference in T2 changes after LPD between medial and lateral areas of patellar cartilage. Evidence Level: 2 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

Abstract Background Recurrent lateral patellar dislocation (RLPD) poses a significant threat to patients’ quality of life due to knee pain, patellofemoral cartilage damage, and potential traumatic arthritis. Predictive scoring systems have been developed to assess the risk of RLPD; however, their relative accuracy remains uncertain. Purpose To investigate the accuracy of the multiple regression models to predict the individual risk of recurrent LPD. Methods The Patellar Instability probability calculator (PIP), Recurrent Instability of the Patella Score (RIP), and Patellar Instability Severity Score (PIS) scoring rules were measured in 171 patients with a history of patellar dislocation and 171 healthy individuals. Three prediction models were calculated based on the data to predict the risk of recurrent lateral patellar dislocation. The inter-observer and intra-observer reliability of each measurement parameter was evaluated. The predictive capacity of the three-prediction model was investigated using the receiver operating characteristic curve. Results In the case group of 171 patients, PIS accurately predicted recurrent lateral Patella dislocation in 143 patients. RIP was 96, and PIP was 83. The positive predictive values were 92.9%, 64%, and 68% respectively. In the control group of 171 patients, the PIS was validated in 160 patients who would not experience dislocations. RIP was 117, and PIP was 50. The negative predictive values were 85.1%, 60.9%, and 36.2%, respectively. The area under the curve score for the PIS was 0.866, and the RIP was 0.673. the PIP was 0.678. Conclusion RIP and PIP did not work to predict LPD. PIS can accurately predict recurrent lateral patellar dislocation. It can aid doctors in making treatment decisions. Level of evidence Level III, retrospective comparative study.

Background: Recurrent lateral patellar dislocation (RLPD) poses a significant threat to patients' quality of life due to knee pain, patellofemoral cartilage damage, and potential traumatic arthritis. Predictive scoring systems have been developed to assess the risk of RLPD; however, their relative accuracy remains uncertain. Purpose: To investigate the accuracy of the multiple regression models to predict the individual risk of recurrent LPD. Methods: The Patellar Instability probability calculator (PIP), Recurrent Instability of the Patella Score (RIP), and Patellar Instability Severity Score (PIS) scoring rules were measured in 171 patients with a history of patellar dislocation and 171 healthy individuals. Three prediction models were calculated based on the data to predict the risk of recurrent lateral patellar dislocation. The inter-observer and intra-observer reliability of each measurement parameter was evaluated. The predictive capacity of the three-prediction model was investigated using the receiver operating characteristic curve. Results: In the case group of 171 patients, PIS accurately predicted recurrent lateral Patella dislocation in 143 patients. RIP was 96, and PIP was 83. The positive predictive values were 92.9%, 64%, and 68% respectively. In the control group of 171 patients, the PIS was validated in 160 patients who would not experience dislocations. RIP was 117, and PIP was 50. The negative predictive values were 85.1%, 60.9%, and 36.2%, respectively. The area under the curve score for the PIS was 0.866, and the RIP was 0.673. the PIP was 0.678. Conclusion: RIP and PIP did not work to predict LPD. PIS can accurately predict recurrent lateral patellar dislocation. It can aid doctors in making treatment decisions. Level of evidence: Level III, retrospective comparative study. [ABSTRACT FROM AUTHOR]

Abstract Background The evidence regarding the usefulness of assessment tools to support decisions of return-to-sport after surgery for patellar instability is scarce. The purpose of this study was therefore to explore the feasibility of functional tests assessing readiness for return-to-sport six months after patellar stabilizing surgery. However, there is little evidence on what a functional assessment should include to support these decisions following surgery for patellar instability. Therefore the purpose of this study was to explore the feasibility of functional tests assessing readiness for return-to-sport six months after patellar stabilizing surgery. Methods In this cross-sectional study a prospective cohort of 78 patients were subjected to a range of return-to-sport readiness tests at six months after surgery for patellar instability with an “a la carte” approach. Lower Quarter Y-Balance Test (YBT-LQ), single-legged hop tests and isokinetic strength tests were performed. In addition, self-reported function was measured with the Banff Patellofemoral Instability Instrument 2.0 (BPII) and Norwich Patellar Instability score (NPI). Return-to-sport clearance criteria were defined as: ≤4 cm YBT-LQ anterior reach difference between legs, leg-symmetry-index (LSI) ≥ 95% in the YBT-LQ composite score, mean sum score LSI ≥ 85% of all single-leg hop tests and LSI ≥ 90% in isokinetic quadriceps strength. Results Sixty-four patients (82%) were able to complete all functional tests, while only eleven (14%) patients were deemed ready for return-to-sport, passing all return-to-sport clearance criteria. Patients with bilateral problems demonstrated worse performance in the contralateral leg, which resulted in higher LSI scores compared to individuals with unilateral instability. A supplementary finding was that the extent of surgery (MPFL-R only versus combined surgery) did not predict and mainly did not affect self-reported function or functional performance at the follow-up. Conclusion The functional assessment used in the current study seems feasible to conduct at six months after patellar stabilizing surgery. However, current suggested clearance standards and the use of leg-symmetry-index seems inappropriate for patients with patellar instability. Therefore, further exploration of appropriate tests and return-to-sport clearance criteria is justified. Trial registration clinicaltrial.gov, NCT05119088. Registered 12.11.2021 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05119088 .

Background: The evidence regarding the usefulness of assessment tools to support decisions of return-to-sport after surgery for patellar instability is scarce. The purpose of this study was therefore to explore the feasibility of functional tests assessing readiness for return-to-sport six months after patellar stabilizing surgery. However, there is little evidence on what a functional assessment should include to support these decisions following surgery for patellar instability. Therefore the purpose of this study was to explore the feasibility of functional tests assessing readiness for return-to-sport six months after patellar stabilizing surgery. Methods: In this cross-sectional study a prospective cohort of 78 patients were subjected to a range of return-to-sport readiness tests at six months after surgery for patellar instability with an "a la carte" approach. Lower Quarter Y-Balance Test (YBT-LQ), single-legged hop tests and isokinetic strength tests were performed. In addition, self-reported function was measured with the Banff Patellofemoral Instability Instrument 2.0 (BPII) and Norwich Patellar Instability score (NPI). Return-to-sport clearance criteria were defined as: ≤4 cm YBT-LQ anterior reach difference between legs, leg-symmetry-index (LSI) ≥ 95% in the YBT-LQ composite score, mean sum score LSI ≥ 85% of all single-leg hop tests and LSI ≥ 90% in isokinetic quadriceps strength. Results: Sixty-four patients (82%) were able to complete all functional tests, while only eleven (14%) patients were deemed ready for return-to-sport, passing all return-to-sport clearance criteria. Patients with bilateral problems demonstrated worse performance in the contralateral leg, which resulted in higher LSI scores compared to individuals with unilateral instability. A supplementary finding was that the extent of surgery (MPFL-R only versus combined surgery) did not predict and mainly did not affect self-reported function or functional performance at the follow-up. Conclusion: The functional assessment used in the current study seems feasible to conduct at six months after patellar stabilizing surgery. However, current suggested clearance standards and the use of leg-symmetry-index seems inappropriate for patients with patellar instability. Therefore, further exploration of appropriate tests and return-to-sport clearance criteria is justified. Trial registration: clinicaltrial.gov, NCT05119088. Registered 12.11.2021 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05119088. [ABSTRACT FROM AUTHOR]

Introduction: Medial patellofemoral ligament reconstruction (MPFLR) is the most commonly used surgical treatment for patients with lateral patellar dislocation (LPD). It is still poorly understood whether or not MPFLR has a contributory effect on decreasing patellar height. Materials and methods: Forty-five patients who underwent isolated MPFLR for LPD and patella alta were evaluated with a mean follow-up period of 24 months (22–25 months). Knee joint functions were evaluated by Banff patellofemoral instability instrument (BPII) 2.0 scores and Kujala scores. Patellofemoral engagement and stability were assessed by the patella tilt angle (PTA) and patellar congruence angle (PCA) measured by CT scans, and the patellar-glide test. Patellar height was calculated on lateral radiographs according to three methods: Caton-Deschamps ratios (CDR), Insall-Salvati ratios (ISR), and Blackburne-Peel ratios (BPR). A threshold value of p < 0.05 denoted a statistically significant difference. Results: Significant improvements were found in both BPII 2.0 scores, which increased from 41.7 to 77.8 (p < 0.001) and Kujala scores, which increased from 49.2 to 85.5 (p < 0.001). Post-operative PTAs and PCA decreased from 19.6 ± 8.8 to − 3.4 ± 6.2, and from 24.6 ± 7.3 to 13.1 ± 3.8 degrees respectively (p < 0.001). No patients showed lateral translation more than grade II in the patellar-glide test. Regarding patellar height, a tiny reduction (Δ = 0.02, Δ max = 0.09) was discovered in using CDR (p = 0.027), rather than ISR or BPR. All measurements of radiographic indices had an excellent intra- and inter-rater reliability (ICC > 0.75). Conclusions: Isolated anatomic MPFLR is sufficient to achieve good clinical outcomes, as well as patellofemoral stability and high rates of return-to-sport. However, it is unclear if the reconstructed MPFL has a contributory effect on reducing patellar height. [ABSTRACT FROM AUTHOR]

Background: Following first-time lateral patellar dislocation (FTLPD), most patients are treated conservatively, although 50% of patients will have recurrent dislocations. Typically, radiographs followed by CT and/or MRI are used to assist the clinician in determining treatment strategy and, combined with clinical findings, intraarticular free bodies (CT/MRI), significant medial patellofemoral ligament (MPFL) tear (MRI) and lateral displacement of the patella (CT) form relative indications for surgery. Methods: Radiographs, MRI and CT knee studies of 34 patients after lateral patellar dislocation (26 FTLPD) were evaluated for intraarticular free bodies, patellar/trochlear fracture, lateral femoral condyle compression, MPFL tear, tibial tuberosity-trochlear groove (TT-TG) distance, and surgery indications. Free bodies and fractures were also evaluated on knee radiographs. FTLPD was analyzed as a subgroup. Surgical indications were compared between imaging modalities. Results: Among FTLPD (26 patients); free bodies were identified in 13 and 19 patients using MRI and CT respectively, compared with 5 patients on radiographs; this was statistically significant. In 8 cases surgery was indicated based on MPFL tear (MRI) combined with lateral patellar displacement (CT). When MRI and CT results were combined, 21 of 26 patients had imaging indications for surgery compared to 13 and 19 patients based on the MRI or CT alone, respectively. CT was statistically better than MRI alone or MRI with radiographs in identifying patients requiring surgery. Conclusion: An MRI or CT study is warranted to determine the need for surgery. A second imaging study (different from the first) should be considered, if surgical indication was not established from the initial study or clinical presentation. [ABSTRACT FROM AUTHOR]

Background: Patellar dislocation is a common injury in children and adolescents. There is a lack of information about concomitant osteochondral lesions in these patients. Hypothesis: We hypothesized that the likelihood of chondral or osteochondral lesions would increase with each prior patellar dislocation and that the appearance of lesions in surgically treated children and adolescents would be influenced by age, sex, injury mechanism, and body mass index (BMI). Study Design: Case-control study; Level of evidence, 3. Methods: Inclusion criteria were (1) age <18 years, (2) surgical treatment with diagnostic arthroscopy of the knee including description of chondral and osteochondral lesions, and (3) maximum time period between the last patellar dislocation and presentation in our department of 6 weeks and maximum of 4 weeks between presentation and surgery. A total of 153 children (173 knees) with a mean age of 13.0 ± 2.1 years were included. All surgical reports and intraoperative arthroscopic imaging were analyzed retrospectively for the location and severity of lesions. The likelihood of lesions was calculated with multiple stepwise regression models regarding injury mechanism, number of dislocations, sex, age, physeal closure, and BMI. Results: The regression model to predict femoral lesions was statistically significant (χ2[5] = 26.55; P <.001) and identified male sex, BMI ≥25, traumatic injury mechanism, and physeal closure as independent factors associated with the appearance of femoral lesions. The second regression model predicting the appearance of patellar lesions was also statistically significant (χ2[4] = 26.07; P <.001) and identified the traumatic injury mechanism as a single independent predictor for patellar lesions. Conclusion: BMI ≥25, male sex, and physeal closure were factors significantly associated with femoral chondral and osteochondral lesions in our cohort. In case of traumatic lateral patellar dislocation (LPD), the likelihood of patellar and femoral chondral and osteochondral lesions is significantly higher than in nontraumatic LPD. Early magnetic resonance imaging and surgical treatment should be considered in obese patients, male patients, and patients with physeal closure and after traumatic LPD. [ABSTRACT FROM AUTHOR]

Background: Increased tibial tuberosity–trochlear groove (TT-TG) distance is an important indicator of medial tibial tubercle transfer in the surgical management of lateral patellar dislocation (LPD). Changes to TT-TG distance are determined by a combination of several anatomical factors. Purpose: To (1) determine the anatomical components related to increased TT-TG distance and (2) quantify the contribution of each to identify the most prominent component. Study Design: Case-control study; Level of evidence, 3. Methods: Included were 80 patients with recurrent LPD and 80 age- and body mass index–matched controls. The 2 groups were compared in TT-TG distance and its related anatomical components: tibial tubercle lateralization (TTL), trochlear groove medialization, femoral anteversion, tibiofemoral rotation (TFR), tibial torsion, and mechanical axis deviation (MAD). The Pearson correlation coefficient (r) was calculated to evaluate the association between increased TT-TG distance and its anatomical parameters, and factors that met the inclusion criteria of P <.05 and r ≥ 0.30 were analyzed via stepwise multivariable linear regression analysis to predict TT-TG distance. Results: The LPD and control groups differed significantly in TT-TG distance, TTL, TFR, and MAD (P <.001 for all). Increased TT-TG distance was significantly positively correlated with TTL (r = 0.376; P <.001), femoral anteversion (r = 0.166; P =.036), TFR (r = 0.574; P <.001), and MAD (r = 0.415; P <.001), and it was signficantly negatively correlated with trochlear groove medialization (r = −0.178; P =.024). The stepwise multivariable analysis revealed that higher TTL, excessive knee external rotation, and excessive knee valgus were statistically significant predictors of greater TT-TG distance (P <.001 for all). The standardized estimates that were used for evaluating the predictive values were larger for TFR compared with those for TTL and MAD. Conclusion: TTL, TFR, and MAD were the main independent anatomical components associated with increased TT-TG distance, with the most prominent component being TFR. The association of TT-TG distance to each component analyzed in our study may help guide surgical planning. [ABSTRACT FROM AUTHOR]

Background: Predicting the risk of recurrence is of great interest when counseling patients after primary lateral patellar dislocation (LPD). Purpose: To investigate a multivariate model to predict the individual risk of recurrent LPD. Study Design: Case-control study; Level of evidence, 3. Methods: The study population included patients with primary LPD, knee imaging, and a minimum 2-year follow-up after nonoperative treatment. Data including patient characteristics and anatomic patellar instability risk factors were collected retrospectively from 7 national study centers. Bivariate and multivariate regression analyses were carried out to identify risk factors for recurrent LPD and to generate an accuracy-optimized model for out-of-sample prediction. Results: In total, 115 of 201 patients (57%) experienced recurrent LPD within 2 years after primary LPD. Age ≤16 years at primary LPD (odds ratio [OR], 5.0), history of contralateral instability (OR, 2.4), and trochlear dysplasia (Dejour type B-D: OR, 2.5; lateral trochlear inclination ≤12°: OR, 2.7) were significant risk factors for recurrent LPD (P <.05). The prediction accuracy including these 3 risk factors was 79%. Patella alta, an increased tibial tubercle to trochlear groove distance, and patellar tilt had neither an association with increased recurrence rates nor an influence on prediction accuracy of recurrent LPD. Conclusion: Young age and trochlear dysplasia are major risk factors for early recurrent LPD. A multivariate model including age at primary LPD, lateral trochlear inclination, and history of contralateral LPD achieved the highest prediction accuracy. Based on these findings, the patellar instability probability calculator is proposed to estimate the individual risk of early recurrence when counseling patients after primary LPD. [ABSTRACT FROM AUTHOR]

Background: Trochlear dysplasia (TD) is a key predisposing risk factor for patellar instability (PI) and lateral patellar dislocation (LPD) injuries. It is useful to understand the reliability of radiographic findings of TD and the accuracy of knee radiographs in diagnosing patients with recent LPD. Purpose: The purposes of our study are to evaluate the inter-rater reliability of specific radiographic signs of PI and staging of TD between radiologists and orthopedic surgeons, and to identify which findings are associated with recent LPD. Methods: This retrospective study comprised 336 patients aged 8 to 18 who obtained knee radiographs over a 3-year period. Two radiologists and two orthopedic surgeons, blinded to patient history, examined radiographs for indicators of PI. Using data from 19 confirmed LPD cases and 317 controls, inter-observer agreement (kappa, Pearson's correlation coefficient) was assessed, as was the odds ratio for likelihood of LPD. Results: There was nearly perfect agreement between radiologists for patella-tendon ratios (Pearson's correlation coefficient 0.8377, P < 0.0001) and discrimination between normal knees and high-grade TD (kappa 0.9213, P < 0.0001). There is fair agreement between radiologists and surgeons distinguishing between normal knees and high-grade TD (kappa 0.5843, P < 0.0001). Lateral knee radiographs interpreted as high-grade TD were highly predictive of LPD (odds ratio 7.58–54.8) among all readers. Conclusions: There is high agreement between radiologists when evaluating lateral knee radiographs for signs of TD, validating the results of prior literature. Radiographic findings TD, patella alta, and effusion are variable predictors of recent LPD, greatest among patients with TD. [ABSTRACT FROM AUTHOR]

Background: Medial patellofemoral ligament (MPFL) reconstruction is an established operative procedure to restore medial restraining force in patients with patellar instability. In the setting of a shallow sulcus, it is unclear whether an isolated MPFL reconstruction is sufficient to restore patellofemoral stability. Hypothesis: Progressively increasing the sulcus angle would have an adverse effect on the ability of an MPFL reconstruction to restrain lateral patellar motion. Study Design: Controlled laboratory study. Methods: Seven fresh-frozen human cadaveric knees were harvested and prepared for experimentation. Each specimen was run through the following test conditions: native, lateral retinacular release, lateral retinacular repair, MPFL release, MPFL reconstruction, and MPFL reconstruction with trochlear flattening. Four 3-dimensional printed wedges (10°, 20°, 30°, and 40°) were created to insert beneath the native trochlea to raise the sulcus angle incrementally and simulate progressive trochlear flattening. For each test condition, the knee was positioned at 0°, 15°, 30°, and 45° of flexion, and the force required to displace the patella 1 cm laterally at 10 mm/s was measured. Group comparisons were made with repeated measures analysis of variance. Results: In the setting of an MPFL reconstruction, as the trochlear groove was incrementally flattened, the force required to laterally displace the patella progressively decreased. A 10° increase in the sulcus angle significantly reduced the force at 15° (P =.01) and 30° (P =.03) of knee flexion. The force required to laterally displace the patella was also significantly lower at all knee flexion angles after the addition of the 20°, 30°, and 40° wedges (P ≤.05). Specifically, a 20° increase in the sulcus angle reduced the force by 29% to 36%; a 30° increase, by 35% to 43%; and a 40° increase, by 40% to 47%. Conclusion: Despite an MPFL reconstruction, the force required to laterally displace the patella decreased as the sulcus angle was increased in our cadaveric model. Clinical Relevance: An isolated MPFL reconstruction may not be sufficient to restore patellar stability in the setting of a shallow or flat trochlea. Patients with an abnormal sulcus angle may have recurrent instability postoperatively if treated with an isolated MPFL reconstruction. [ABSTRACT FROM AUTHOR]

Background: Combined injuries observed with first-time lateral patellar dislocation (LPD) of the knee, particularly significant soft tissue injury, can inform surgical intervention criteria., Purpose: The purpose of this study was to compare MRI findings in LPD to surgical correlation concerning meniscal pathology as a guide for surgical management., Study Design: Retrospective case series, Level of evidence, 4., Methods: A retrospective review was conducted of 355 cases of patients with lateral patellar dislocation from 2012 to 2022. Imaging was reviewed by musculoskeletal radiologists blinded to surgical results for evidence of soft tissue injury, and associated arthroscopic data and operative reports were reviewed., Results: Out of 44 cases of LPD in 42 patients who underwent MPFL reconstructive surgery, 27 (61%) cases had grade 2a or higher signal changes in the anterior horn of the lateral meniscus, of which 10 (23%) had grade 3 signal changes. There were zero cases of meniscal tear in these cases upon review of operative reports and arthroscopic images., Conclusion: MRI findings of signal alterations in the lateral meniscus post-LPD may not indicate an actual tear. This could aid in surgical decision-making in primary LPD management., (© 2024 Professor P K Surendran Memorial Education Foundation. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Introduction: Trochlear dysplasia (TD) is a condition that is characterized by the presence of either a flat or convex trochlear, which impedes the stability of the patellofemoral joint (PFJ). The PFJ function is dependent on many different structures that surround the knee joint. The aim of this study was to analyse all the muscle components around the PFJ and identify whether gross muscle imbalance could contribute to the stability of the patella in TD. Material and methods: The average cross-sectional area (CSA) and cross-sectional area ratio (CSAR) of each muscle of the thigh region in subtypes of TD was evaluated and compared to normal knee joints. Ninety-eight patients (196 knees in total) were included in the study. Results: Of the 196 knee joints that were reviewed, 10 cases were found to be normal. In total, 186 cases were positive for TD. The majority consisted of type C. The hamstring muscles showed variable results. The vastus medialis muscle was larger in comparison to the vastus lateralis muscle over all the different TD subtypes; however, no statistical significance was identified. There was a marked statistical significance between the quadriceps and hamstring muscles, especially when comparing this to the normal knees within our cohort. Conclusions: This study revealed no significant difference in the effect of the thigh muscle CSA on the stability of the PFJ in TD. Further research is required to establish the roles of the different muscles around PFJ in the prevention of TD dislocation. [ABSTRACT FROM AUTHOR]

Background: In most cases, lateral patellar dislocation (LPD) is accompanied by chondral injury and may initiate gradual degeneration of patellar cartilage, which might be detected with a T 2 mapping, a well-established method for cartilage lesions assessment., Purpose: To examine short-term consequences of single first-time LPD in teenagers by T 2 mapping of the patellar-cartilage state., Study Type: Prospective., Population: 95 patients (mean age: 15.1 ± 2.3; male/female: 46/49) with first-time, complete, traumatic LPD and 51 healthy controls (mean age: 14.7 ± 2.2, male/female: 29/22)., Field Strength/sequence: 3.0 T; axial T 2 mapping acquired using a 2D turbo spin-echo sequence., Assessment: MRI examination was conducted 2-4 months after first LPD. T 2 values were calculated in manually segmented cartilage area via averaging over three middle level slices in six cartilage regions: deep, intermediate, superficial layers, and medial lateral parts., Statistical Tests: ANOVA analysis with Tukey's multiple comparison test, one-vs.-rest logistic regression analysis. The threshold of significance was set at P < 0.05., Results: In lateral patellar cartilage, a significant increase in T 2 values was found in deep and intermediate layers in both patient groups with mild (deep: 34.7 vs. 31.3 msec, intermediate: 38.7 vs. 34.6 msec, effect size = 0.55) and severe (34.8 vs. 31.3 msec, 39.1 vs. 34.6 msec, 0.55) LPD consequences as compared to controls. In the medial facet, only severe cartilage damage showed significant prolongation of T 2 times in the deep layer (34.3 vs. 30.7 msec, 0.55). No significant changes in T 2 values were found in the lateral superficial layer (P = 0.99), whereas mild chondromalacia resulted in a significant decrease of T 2 in the medial superficial layer (41.0 vs. 43.8 msec, 0.55)., Data Conclusion: The study revealed substantial difference in T 2 changes after LPD between medial and lateral areas of patellar cartilage., Evidence Level: 2 TECHNICAL EFFICACY STAGE: 2., (© 2023 International Society for Magnetic Resonance in Medicine.)

Purpose: The primary goal was to describe the injury patterns in a population of primary (first time) lateral patellar dislocators (LPD) to lend clarity to commonly held notions about injury patterns in this population.Methods: A prospective study identifying patients presenting with LPD between 2008 and 2012. Inclusion criteria were a history and physical exam consistent with primary LPD, and an MRI consistent with the diagnosis without other significant ligamentous injury. On MRI, location of cartilage, medial patellofemoral ligament (MPFL) injury, and bone bruising were noted. Severity was categorized as partial or complete for MPFL and cartilage lesions. Anatomic patellar instability risk factors (patella alta, trochlear dysplasia, increased TT-TG, and lateral patella tilt) were recorded and compared to the injury patterns.Results: This study involved 157 patients; 107 patients were skeletally mature. Of the 157 patients, 26 had surgery for this injury due to clinician-perceived need for cartilage debridement. MPFL injury severity was complete rupture (N = 69, 44%), partial (N = 67, 43%), and none (N = 19, 13%). MPFL injury location was isolated femoral (N = 16, 10%), isolated patella (N = 26, 17%), isolated mid-substance (0%), multiple locations (N = 95, 61%), and none (N = 20, 13%). Chondral injury location was patella (N = 67, 43%), lateral femoral condyle (N = 11, 7%), multiple locations (N = 53, 34%), and none (N = 26, 17%). A majority (61%) of patellar chondral lesions were at its inferomedial aspect; all medial patellar retinacular partial injuries involved the inferomedial aspect of the patella, consistent with the insertion of the medial patellotibial ligament (MPTL). Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. No clear relationship was found between/across the location and/or severity of bone bruising, MPFL, or chondral injury.Clinical Relevance: Underlying anatomic patellar instability risk factors defined by MRI, do not predict injury patterns. MPFL and chondral injury, as well as bone bruising, are common following LPD. The medial patellotibial ligament is torn in patellar-based medial retinacular injuries, based on MRI injury location. Skeletal immaturity plays a role in the location of the injury pattern with isolated patellar-based MPFL/chondral injury being more common in the skeletally immature patient. Sex does not appear to be a factor in injury patterns after primary LPD. Knowledge of these injury trends will help focus the clinician in injury evaluation when managing primary patellar dislocations.Level Of Evidence: Case series, Level IV. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the correlation between injury patterns of the medial patellofemoral ligament (MPFL) and vastus medialis obliquus (VMO) after acute first-time lateral patellar dislocation (LPD) in adults.Methods: Magnetic resonance imaging (MRI) was prospectively performed in 132 consecutive adults with acute first-time LPD. Images were acquired and evaluated using standardized protocols. Injury patterns of MPFL were grouped by location and severity for analysis of the prevalence of VMO injury.Results: MRI demonstrated VMO injury in 63 (47.7%) patients. Twenty (38.5%) and 43 cases (56.6%) were present in partial and complete MPFL tear subgroups, respectively. Compared with partial MPFL tears, complete tears showed a higher prevalence of VMO injury (P = 0.044). The mean coronal (28.5 mm) and mean sagittal VMO elevations (20.7 mm) were higher in the complete MPFL tear subgroup than in the partial tear subgroup (19.8 mm, P = 0.005; 11.9 mm, P < 0.001). No correlations were identified between the prevalence of VMO injury and location subgroups of MPFL injury (n.s.). Mean VMO elevations were higher in isolated femoral-side (FEM) and combined MPFL tear (COM) subgroups (mean coronal VMO elevation of 29 mm and mean sagittal VMO elevation of 20.8 mm in the FEM subgroup; mean coronal VMO elevation of 29.6 mm and mean sagittal VMO elevation of 23.1 mm in the COM subgroup) than in the isolated patellar-side MPFL tear (PAT) subgroup (P = 0.022, P < 0.001) (mean coronal VMO elevation of 20.7 mm and mean sagittal VMO elevation of 10.6 mm).Conclusions: Complete MPFL tear predisposes to VMO injury and has a higher elevation of torn VMO after acute first-time LPD in adults. Isolated femoral-side and combined MPFL tears predispose to higher elevation of torn VMO.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Background: Patellofemoral cartilage deterioration and osteoarthritis are reported to be associated with recurrent patellar dislocation. However, the association between first-time traumatic patellar dislocation and cartilage deterioration is unknown. Purpose: The aim of this study was to assess long-term cartilage deterioration in the patellofemoral and tibiofemoral joint after conservatively treated traumatic lateral patellar dislocation. Study Design: Case series; Level of evidence, 4. Methods: Twenty patients (mean age, 25 years) who sustained first-time traumatic lateral patellar dislocation with no previous patellofemoral instability symptoms were initially scanned with 1.5-T magnetic resonance imaging (MRI). A follow-up 3-T MRI was conducted, on average, 8 years after first-time lateral patellar dislocation. Subjective instability symptoms and Knee injury and Osteoarthritis Outcome Score were also assessed. Results: In the primary MRI, patellofemoral cartilage injury was seen in 14 of 20 patients (70%). Most (14/15) of the injuries were seen in the patellar cartilage, especially at the medial facet. On the follow-up MRI, patellofemoral cartilage deterioration was visible for all patients. The central patella (P = .005) seemed especially prone to cartilage deterioration during the follow-up. Half of the patients (10/20) had grade 3-4 cartilage lesions in the patellofemoral joint in the follow-up MRI. In the primary MRI, only 1 patient exhibited tibiofemoral joint cartilage lesions, whereas at the time of follow-up, 10 of 20 patients exhibited tibiofemoral cartilage lesions. The majority of these lesions were considered clinically nonsignificant (International Cartilage Repair Society = 1) and were seen in the lateral compartment (6/10, 60%). Of the 14 patients (36%) with injury to the patellar cartilage, 5 reported subsequent instability of the patellofemoral joint, but this was not associated with more significant cartilage deterioration in the follow-up MRI compared with patients without redislocation. Conclusion: While recurrent lateral patellar dislocation is known to lead to degenerative process, a single first-time or infrequently recurring traumatic lateral patellar dislocation also seems to be associated with gradual cartilage deterioration. Traumatic lateral patellar dislocation might initiate gradual degeneration of the cartilage in the patellofemoral joint and can lead to the development of generalized knee osteoarthritis. Instability symptoms of the patellofemoral joint, however, were not related to the severity of the deterioration. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to investigate the injury characteristics of medial patellofemoral ligament (MPFL), and to analyse the correlations between the injury patterns of MPFL and articular cartilage lesions of the lateral femoral condyle in adults with acute lateral patellar dislocation (LPD). Methods: Magnetic resonance (MR) images were prospectively obtained in 121 consecutive adults with acute LPD. Images were acquired using standardised protocols and these were independently evaluated by two radiologists. Results: Forty-eight cases of partial MPFL tear and 71 cases of complete MPFL tear were identified. Injuries occurred at an isolated femoral attachment (FEM) in 48 cases, an isolated patellar insertion (PAT) in 36 cases and an isolated mid-substance (MID) in five cases. More than one site of injury to the MPFL (COM) was identified in 30 cases. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 4.2% (2/48) and 6.3% (3/48) in the FEM subgroup, 19.4% (7/36) and 22.2% (8/36) in the PAT subgroup and 6.7% (2/30) and 13.3% (4/30) in the COM subgroup, respectively. The PAT subgroup showed significantly higher prevalence rate of chondral and osteochondral lesions in the lateral femoral condyle when compared with the FEM subgroup. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 8.5% (6/71) and 19.7% (14/71) in the complete MPFL tear subgroup and 10.4% (5/48) and 4.2% (2/58) in the partial MPFL tear subgroup, respectively. The subgroup of the complete MPFL tear showed significantly higher prevalence rate of osteochondral lesions in the lateral femoral condyle when compared with the subgroup of the partial MPFL tear. Conclusions: Firstly, the MPFL is most easily injured at the FEM, and secondly at the PAT in adults after acute LPD. The complete MPFL tear is more often concomitant with osteochondral lesions of the lateral femoral condyle than the partial MPFL tear. The isolated patellar-sided MPFL tear is more easily concomitant with chondral lesions and osteochondral lesions of the lateral femoral condyle than the isolated femoral-sided MPFL tear. [ABSTRACT FROM AUTHOR]

A 14-year-old girl presented with left knee pain and swelling after an injury. Magnetic resonance (MR) imaging showed a transient lateral patellar dislocation with patellar osteochondral fracture, medial patellofemoral ligament tear and underlying femoral trochlear dysplasia. Open reduction and internal fixation of the osteochondral fracture, plication of the medial patellar retinaculum and lateral release were performed. As lateral patellar dislocation is often clinically unsuspected, an understanding of its characteristic imaging features is important in making the diagnosis. Knowledge of the various predisposing factors for patellar instability may also influence the choice of surgical management. We also discuss signs of acute injury and chronic instability observed on MR imaging, and the imaging features of anatomical variants that predispose an individual to lateral patellar dislocation. Treatment options and postsurgical imaging appearances are also briefly described. [ABSTRACT FROM AUTHOR]

Objectives The purpose of this study was to investigate the injury characteristics of medial patellofemoral ligament (MPFL), and to analyse the correlations between the injury patterns of MPFL and articular cartilage lesions of the lateral femoral condyle in children and adolescents with acute lateral patellar dislocation (LPD). Methods Magnetic resonance (MR) images were prospectively obtained in 127 consecutive children and adolescents with acute LPD. Images were acquired using standardised protocols and these were independently evaluated by two radiologists. Results Fifty-four cases of partial MPFL tear and 69 cases of complete MPFL tear were identified. Injuries occurred at an isolated patellar insertion (PAT) in 47 cases, an isolated femoral attachment (FEM) in 41 cases and an isolated mid-substance (MID) in four cases. More than one site of injury to the MPFL (COM) was identified in 31 cases. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 23.4% (11/47) and 29.8% (14/47) in the PAT subgroup, 7.3% (3/41) and 9.8% (4/41) in the FEM subgroup and 25.8% (8/31) and 32.3% (10/31) in the COM subgroup, respectively. The PAT and COM subgroups showed significantly higher prevalence rate of chondral and osteochondral lesions in the lateral femoral condyle when compared with the FEM subgroup. The prevalence rate of chondral and osteochondral lesions of the lateral femoral condyle were 17.4% (12/69) and 30.4% (21/69) in the complete MPFL tear subgroup and 20.4% (11/54) and 13% (7/54) in the partial MPFL tear subgroup, respectively. The subgroup of the complete MPFL tear showed significantly higher prevalence rate of osteochondral lesions in the lateral femoral condyle when compared with the subgroup of the partial MPFL tear. Conclusions Firstly, the MPFL is most easily injured at the PAT, and secondly at the FEM in children and adolescents after acute LPD. The complete MPFL tear is more often concomitant with osteochondral lesions of the lateral femoral condyle than the partial MPFL tear. The isolated patellar-sided MPFL tear and the combined MPFL tear are more easily concomitant with chondral lesions and osteochondral lesions of the lateral femoral condyle than the isolated femoral-sided MPFL tear. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The purpose of this study was to investigate the accuracy of high-frequency ultrasonography in the diagnosis of injuries of medial patellofemoral ligaments (MPFLs), analyse the characteristics of MPFL injury and correlations between injury of the MPFL and articular cartilage of the inferomedial patella in patients with acute traumatic lateral patellar dislocation. Methods: High-frequency sonographic images of 49 patients with acute traumatic lateral patellar dislocations treated surgically were reviewed. The χ 2 tests were performed for statistical analysis. Results: Twenty-eight cases of complete MPFL tear and 21 cases of partial MPFL tear were identified in operation, with 27 cases of MPFL tear located at their femoral attachment, 21 cases of tear at the patellar attachment and one case of midsubstance tear. The diagnostic accuracy of sonography regarding partial MPFL tear and complete MPFL tear was 89.8% and 89.8%. Among the patients with MPFL tear at the patellar attachment, eight and six cases were concomitant with chondral and osteochondral lesions in the inferomedial patella, respectively, in contrast to nine and six cases in patients with MPFL tear at the femoral attachment, respectively. There was no significant difference between the two locations described above regarding the prevalence rates of chondral or osteochondral lesions of the inferomedial patella (P =0.732, P =0.614). Among the patients with complete MPFL tear, 12 and 10 cases were concomitant with chondral and osteochondral lesions in the inferomedial patella, respectively, while six and two cases were concomitant with partial MPFL tear. There was no significant difference between the two types of injuries discussed above on the prevalence rates of chondral lesions of the inferomedial patella (P =0.305), but the prevalence rate of osteochondral lesions between the two types of injuries discussed above was statistically different (P =0.035). Conclusions: The MPFL is most easily injured at the femoral attachment, secondly at the patellar attachment. High-frequency ultrasonography is an accurate method in the diagnosis of an MPFL tear. There are neither significant differences on the prevalence rates of chondral or osteochondral lesions of the inferomedial patella between locations of MPFL injuries, nor significant difference on the prevalence rates of chondral lesions between MPFL injury types; but the complete MPFL tear is more often concomitant with inferomedial patellar osteochondral lesions than the partial MPFL tear. [Copyright &y& Elsevier]

Purpose: Medial patellofemoral ligament (MPFL) reconstruction has been performed to treat recurrent patellar dislocation. However, the effects on patellar tracking have not been well documented, particularly in patients. The purpose of this study is to compare patellar tracking pattern and chondral status at MPFL reconstruction with those at second-look arthroscopy. Methods: Between 1999 and 2008, 71 patients with recurrent patellar dislocation underwent MPFL reconstruction using a double-looped semitendinosus tendon. Of these, 25 knees in 24 patients underwent second-look arthroscopy (at 6-26 months after initial surgery), forming the subject for the present study. No other surgical procedures such as tibial tuberosity transfer, lateral release, or osteotomy were performed in any patients. To assess the patellar tracking pattern, the position of the patella on femoral groove was evaluated arthroscopically during passive knee motion through lateral suprapatellar portal. Results: Before MPFL reconstruction, the patella in all patients was shifted laterally throughout the entire range of knee motion. Immediately after MPFL reconstruction, patellar malalignment was corrected in all cases. On second-look arthroscopy, two different patellar tracking patterns were observed. In 9 knees, the patella was located on the center of the femoral groove throughout the range of motion. Meanwhile, in the remaining 16 knees, the patella was shifted laterally at knee extension and migrated to the center of femoral groove with increased knee flexion. No significant deteriorations in chondral status were seen on second-look arthroscopy. Conclusion: The present study revealed that not all improved patellar trackings after MPFL reconstruction remained intact at follow-up. Chondral status in patellofemoral joint was not aggravated by MPFL reconstruction. Level of evidence: Therapeutic studies, Level IV. [ABSTRACT FROM AUTHOR]

Aim of this cadaveric biomechanical study was to describe the detailed anatomy of the static medial patellar stabilizers and further determine the role of each of them in preventing lateral patellar dislocation. Eight cadaver knees, after removing the skin and subcutaneous tissues, were used in the study. The medial patellofemoral ligament (MPFL), the medial retinaculum (MR) the medial patellomeniscal ligament (MPML), and the medial patellotibial ligament (MPTL) were dissected. Their origins, insertions, orientations and sizes were recorded. To the medial stabilizers, a tension of 10 pounds was applied, using a tensiometer held in a semicircular device while the knees were kept in 30 degrees of flexion. Then, the previously described ligaments were dissected and the resultant displacement recorded. The most anatomically distinct structure is the MPFL, whose length varies from 45-50 mm, and its width from 10-20 mm at its origin (medial femoral epicondyle) to 20-30 mm at its insertion to the patella. The "meshing" of the MPFL fibers to the fibers of the vastus medialis obliquus (VMO) close to its patellar insertion was the most interesting and very important finding. The contribution of MPFL to medial stability was more than 50%. Of the remaining ligaments, MPML contributes 24% and the MPTL and MR contribute only 13% respectively. The MPFL is the strongest medial static patellar stabilizer. Its contribution to patellar stability against lateral dislocation is far more than 50%, since its meshing with the VMO, shortens its fibers which thus pulls the patella to the medial part of the femoral groove and keeps it in the trochlea during the initial 20 degrees -30 degrees of flexion. [ABSTRACT FROM AUTHOR]

Background: Most patellar dislocations occur in a lateral direction because of a summed lateral force vector and predisposing anatomic risk factors. Medial patellar instability is rare and is a well-recognized iatrogenic complication of an overly aggressive lateral retinacular release. Noniatrogenic medial patellar dislocations are rare. The management of these injuries is not well described., Purpose: To describe the experience of the International Patellofemoral Study Group with patients with noniatrogenic medial patellar dislocation., Study Design: Case series; Level of evidence, 4., Methods: Members of the International Patellofemoral Study Group (N = 64) were surveyed between October 2018 and April 2019. This group was chosen because of its wide referral base and interest in patellar instability. Specialists who had encountered a patient with medial patellar instability were sent a questionnaire inquiring about details of the case, including patient demographics, medical history, level of athletic competition, injury characteristics, and treatment. Cases were confirmed by physical examination records and, in some cases, with findings on advanced radiographic imaging., Results: The survey response rate was 73% (47/64). Three of the 47 specialists (6.4%) reported they had seen a case of noniatrogenic medial patellar dislocation, for a total of 6 cases. Four cases were described as recurrent medial dislocations in the setting of hypermobile Ehlers-Danlos syndrome; 2 were treated nonoperatively, 1 underwent lateral patellofemoral ligament reconstruction, and 1 underwent derotational osteotomies. Two medial-sided patellar dislocations in collegiate athletes were sports-related injuries that required surgical debridement but no ligamentous reconstruction. None of the patients had persistent or recurrent instability at the time of their most recent follow-up., Conclusion: Noniatrogenic medial patellar dislocations are extremely rare. This case review suggests that the treatment of first-time medial patellar instability in patients without known risk factors should follow the same principles as the treatment of lateral instability with no known risk factors, which is nonoperative management. For patients with documented risk factors and recurrence, surgery to address the risk factors may be appropriate., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: A.E.L. has received hospitality payments from Zimmer Biomet. J.F. has received research support from Active Implants, Arthrex, Episurf, Fidia Pharma, JRF Ortho, Moximed, Novartis, Organogenesis, Samumed, Vericel, and Zimmer Biomet; consulting fees from Aastrom Biosciences, Aesculap/B.Braun, Arthrex, Cartiheal, Ceterix, Cook Biotech, DePuy Synthes, Exactech, ISTO Technologies, MedShape, Moximed, Organogenesis, Osiris, Regentis, RTI Surgical, Samumed, Vericel, Zimmer Biomet, and ZKR Orthopedics; speaking fees from Aastrom Biosciences, Arthrex, Moximed, Organogenesis, Vericel, and Zimmer Biomet; and royalties from Arthrex, Biopoly, DePuy Synthes, Organogenesis, Springer, and Thieme Medical Publishers and has stock/stock options in MedShape and Ortho Regenerative Tech. S.N.P. has received education payments from CDC Medical and speaking fees from Synthes. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2021.)

Aims: The purpose of this study was to explore the correlation between femoral torsion and morphology of the distal femoral condyle in patients with trochlear dysplasia and lateral patellar instability., Methods: A total of 90 patients (64 female, 26 male; mean age 22.1 years (SD 7.2)) with lateral patellar dislocation and trochlear dysplasia who were awaiting surgical treatment between January 2015 and June 2019 were retrospectively analyzed. All patients underwent CT scans of the lower limb to assess the femoral torsion and morphology of the distal femur. The femoral torsion at various levels was assessed using the a) femoral anteversion angle (FAA), b) proximal and distal anteversion angle, c) angle of the proximal femoral axis-anatomical epicondylar axis (PFA-AEA), and d) angle of the AEA-posterior condylar line (AEA-PCL). Representative measurements of distal condylar length were taken and parameters using the ratios of the bianterior condyle, biposterior condyle, bicondyle, anterolateral condyle, and anteromedial condyle were calculated and correlated with reference to the AEA, using the Pearson Correlation coefficient., Results: The femoral torsion had a strong correlation with distal condylar morphology. The FAA was significantly correlated with the ratio of the bianterior condyle (r = 0.355; p = 0.009), the AEA-PCL angle (r = 0.340; p = 0.001) and the ratio of the anterolateral condyle and lateral condyle (ALC-LC) (r = 0.309; p = 0.014). The PFA-AEA angle was also significantly correlated with the ratio of the bianterior condyle (r = 0.319; p = 0.008), the AEA-PCL angle (r = 0.231; p = 0.031), and the ratio of ALC-LC (r = 0.261; p = 0.034). In addition, the bianterior condyle ratio showed a significant correlation with the biposterior condyle ratio (r = -0.324; p = 0.027) and the AEA-PCL angle (r = 0.342; p = 0.021)., Conclusion: Increased femoral torsion correlated with a prominent anterolateral condyle and a shorter posterolateral condyle compared with the medial condyle. The deformities of the anterior and posterior condyles are combined deformities rather than being isolated and individual deformities in patients with trochlear dysplasia and patella instability. Cite this article: Bone Joint J 2020;102-B(7):868-873.

Background: Previous studies have acknowledged the medial patellofemoral ligament (MPFL) as the primary stabilizer of the patella, preventing lateral displacement. MPFL reconstruction (MPFL-R) restores stability and functionality to the patellofemoral joint and has emerged as a preferred treatment option for recurrent lateral patellar instability., Purpose: To objectively measure biomechanical characteristics of athletes cleared for return to sport after MPFL-R compared with healthy controls., Study Design: Cohort study; Level of evidence, 3., Methods: A prospective case-control study design was employed on 31 total athletes. Sixteen athletes (6 male, 10 female; mean age, 16.1 ± 2.74 years; 385 ± 189 days after surgery and 235 ± 157 days after return to sport) underwent MPFL-R and were medically cleared to return to sport. This group was matched by age, sex, and activity level to 15 healthy athletes with no history of lower extremity injuries. Athletes and controls completed validated questionnaires as well as hopping, jumping, and cutting tests with 3-dimensional motion analysis and underwent strength, flexibility, laxity, and balance assessments., Results: Participants in the MPFL-R group scored significantly lower (worse) on the International Knee Documentation Committee (IKDC) (89.2 ± 7.6 vs 98.1 ± 2.0, respectively; P = .0005) and significantly higher (worse) on the Tampa Scale for Kinesiophobia (TSK) (32.4 ± 5.0 vs 25.4 ± 6.5, respectively; P = .006) than those in the control group, but there was no difference in the Kujala score (95.6 ± 5.3 vs 98.8 ± 3.0, respectively; P = .06). Participants in the MPFL-R group demonstrated reduced hip and ankle flexion relative to those in the control group ( P < . 05). Participants in the MPFL-R group also took significantly longer to complete the 6-m timed hop test relative to those in the control group ( P < .05). No statistically significant differences were found in anthropometrics, knee extension or flexion strength, hamstring flexibility, hip abduction strength, or joint laxity between the MPFL-R and control groups., Conclusion: The current data indicate that MPFL-R generally restores functional symmetry, while subtle deficits in global power may remain after being released to full activity. Clinicians should ensure that athletes are fully rehabilitated before returning to sport after MPFL-R by emphasizing functional multijoint exercises., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was supported in part by the National Institutes of Health (grant T35DK060444) and University of Cincinnati’s Department of Orthopaedic Surgery. B.M.G. has received educational support from Arthrex and Smith & Nephew. S.N.P. has received educational support from CDC Medical and is a paid speaker/presenter for Synthes. M.G. has received educational support from CDC Medical. G.D.M. receives publishing royalties from Human Kinetics. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Transient lateral patellar dislocation (TLPD) is a common lesion in young adults. Vascular injury as a complication of TLPD has not been previously described. We report a case of descending genicular artery (DGA) injury after TLPD. Immediate angiography demonstrated rupture of DGA. Embolization was performed with sudden interruption of bleeding. DGA injury should be considered as a complication after TLPD and prompt diagnosis and intervention are required. We propose selective embolization as a safe and effective procedure to stop bleeding. [ABSTRACT FROM AUTHOR]

A 14-year-old girl presented with left knee pain and swelling after an injury. Magnetic resonance (MR) imaging showed a transient lateral patellar dislocation with patellar osteochondral fracture, medial patellofemoral ligament tear and underlying femoral trochlear dysplasia. Open reduction and internal fixation of the osteochondral fracture, plication of the medial patellar retinaculum and lateral release were performed. As lateral patellar dislocation is often clinically unsuspected, an understanding of its characteristic imaging features is important in making the diagnosis. Knowledge of the various predisposing factors for patellar instability may also influence the choice of surgical management. We also discuss signs of acute injury and chronic instability observed on MR imaging, and the imaging features of anatomical variants that predispose an individual to lateral patellar dislocation. Treatment options and postsurgical imaging appearances are also briefly described.