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The purpose of this study was to determine the reliability and validity of ultrasonography for measurement of hamstring muscle and semitendinosus (ST) tendon cross-sectional area (CSA). On two consecutive days, muscle anatomical CSA (ACSA) and ST tendon CSA were measured at standardized positions (30%-80% of thigh length; half the distance from the distal muscle-tendon junction to the popliteal crease) on 12 legs using ultrasonography and compared with corresponding magnetic resonance imaging measures. Inter-day intraclass correlation coefficients were good-to-excellent (0.882-0.996) for all assessed muscle and tendon sites. The limits of agreement widths were narrowest (range: 17%-52%) when muscle ACSA was large but were wide at sites with relatively small ACSA (≤184%) and for ST tendon CSA (range: 72%). Results suggest ultrasound-based measures of individual hamstring muscle maximal ACSA are reliable and valid and ST tendon CSA measures are reliable but require comparison with cadaveric or intra-operative measurements to verify validity., (Copyright © 2019 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Variations of the anatomy of the hamstring muscle complex are uncommon. In particular, absence of some or all of the hamstring muscles is rarely described in the literature. This report presents a case of absent semimembranosus musculature detected incidentally on knee magnetic resonance imaging (MRI), then found to be bilateral on MRI of both thighs performed shortly thereafter. Imaging also demonstrated atypical morphologies of the semitendinosus and biceps femoris muscles in both thighs.

Objective: Hamstring muscle deficiency is increasingly recognized as a risk factor for anterior cruciate ligament (ACL) tears. The purpose of this study is to evaluate the vastus medialis to semimembranosus cross-sectional area (VM:SM CSA) ratio on magnetic resonance imaging (MRI) in patients with ACL tears compared to controls., Materials and Methods: One hundred knee MRIs of acute ACL tear patients and 100 age-, sex-, and side-matched controls were included. Mechanism of injury, contact versus non-contact, was determined for each ACL tear subject. The VM:SM CSA was measured on individual axial slices with a novel method using image-processing software. One reader measured all 200 knees and the second reader measured 50 knees at random to assess inter-reader variability. The intraclass correlation coefficient (ICC) was calculated to evaluate for correlation between readers. T-tests were performed to evaluate for differences in VM:SM CSA ratios between the ACL tear group and control group., Results: The ICC for agreement between the two readers was 0.991 (95% confidence interval 0.984-0.995). Acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.44 vs. 1.28; p = 0.005). Non-contact acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.48 vs. 1.20; p = 0.003), whereas contact acute ACL tear patients do not (1.23 vs. 1.26; p = 0.762)., Conclusion: Acute non-contact ACL tears are associated with increased VM:SM CSA ratios, which may imply a relative deficiency in hamstring strength. This study also demonstrates a novel method of measuring the relative CSA of muscles on MRI.

Background: To determine if there is an association between semimembranosus tendinosis and medial meniscal tears using MRI. Methods: A retrospective review of knee 3T MRI scans was performed to determine the presence or absence of medial meniscal tears in patients with semimembranosus tendinosis. All studies were interpreted by two musculoskeletal radiologists. Univariate association for the presence of semimembranosus tendinosis and medial meniscal tears was performed with a Chi-square test followed by logistic regression modelling among statistically significant associations. Results: A total of 150 knee MRI scans were reviewed (age 32.8 ± 7.1 years; 70 females). Semimembranosus tendinosis was present in 66 knees (44%) in the patient population. Semimembranosus tendinosis was present in 81% of patients with meniscal tears versus 36% of patients without meniscal tears (p < 0.0001). This association remained statistically significant when adjusted for age and sex with an adjusted odds ratio of 7.0 (p < 0.0003). Models adjusted for the above covariates and containing the interaction term produced an adjusted odds ratio of 13.0 (p < 0.0001) in men, while in women this association was non-significant with an adjusted odds ratio of 2.0 (p = 0.42). Conclusions: Subjects with semimembranosus tendinosis were seven times more likely to have medial meniscal tears even when adjusting for sex and age. This could help guide the appropriate postmeniscal repair rehabilitation protocol. [ABSTRACT FROM AUTHOR]

Background: Medial meniscal ramp lesions have recently been an area of interest because of their recognized prevalence in association with anterior cruciate ligament (ACL) ruptures. Anatomically, the medial meniscal ramp is composed of the meniscocapsular ligament in continuity with the semimembranosus muscle and the meniscotibial ligament. Diagnosis of ramp semimembranosus complex (RSC) injuries remains challenging, and their prevalence is likely to be underestimated in comparison with ramp lesions. Purpose: To determine the prevalence of RSC lesions after a complete ACL rupture. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective database analysis was performed. The cohort consisted of the first 100 patients with complete ACL rupture confirmed by magnetic resonance imaging (MRI) who underwent knee arthroscopy for ACL reconstruction in 2019. The semimembranosus lesions were identified using MRI by 2 independent radiologists specializing in musculoskeletal imaging. The ramp lesions were initially diagnosed using MRI and then confirmed during arthroscopy by an experienced knee surgeon. The magnitude of rotatory instability was recorded using the pivot-shift test. A multivariate analysis was used to determine the lesions associated with the semimembranosus complex. Results: Of 100 patients, 53 showed lesions of the RSC; among them, 30 ramp lesions were confirmed after arthroscopic evaluation, and 40 semimembranosus lesions (23 without ramp lesion and 17 with ramp lesion) were found using MRI. A positive pivot shift was present in 57% of patients with combined RSC injury (P =.04) compared with 36% in patients without an RSC lesion. Conclusion: Lesions of the RSC were found in more than half of ACL ruptures in this retrospective cohort. Rotational instability could be associated with combined ACL and RSC injury. [ABSTRACT FROM AUTHOR]

Background: The semimembranosus (SM) tendon acts as a secondary dynamic stabilizer of the knee. It restrains external rotation and anterior translation of the medial compartment. Its role in the mechanism of injury during anterior cruciate ligament (ACL) rupture is unknown. Hypothesis: The bone bruise (BB) often detected at the posteromedial tibia in association with acute ACL tear may be related to the traction force from the SM tendon insertion. Magnetic resonance imaging (MRI) alterations can be detectable at the direct arm of the SM tendon in association with acute ACL injury. Study Design: Cross-sectional study: Level of evidence, 3. Methods: In the first study phase, 36 noninjured patients underwent knee MRI. The anatomic appearance of the SM tendon was evaluated. An imaging score for evaluating the SM tendon was developed for the purpose of the study. The intensity (in the axial or sagittal plane), morphology, and thickness of the distal SM tendon was evaluated and scored (4 total points). In the second study phase, 52 patients undergoing acute ACL reconstruction were included. Preoperative MRI was examined and scored, with documentation of BB at the posteromedial tibial plateau. Finally, arthroscopic diagnosis of a ramp lesion was confirmed. Logistic regression analysis was carried out for correlation between an altered MRI scoring system and the presence of BB at the posteromedial tibial plateau, the presence of a ramp lesion, or both. Results: Interrater agreement of 100% was obtained in the noninjured cohort (ie, no alteration found in any patient). The score validation in the cohort of patients with acute ACL injury showed a Cohen κ of 0.78 (interrater agreement, 82.7%). The direct arm of the SM tendon was altered in 35 of 52 patients (67.3%). A ramp lesion of the medial meniscus was arthroscopically detected in 21 patients (40.4%). The presence of BB at the posteromedial tibial plateau was detected in 33 patients (63.5%) and at the posterior medial femoral condyle in 1 (1.9%). Correlation analysis showed a significant association of a pathologic SM score with the presence of BB at the posteromedial tibial plateau (odds ratio = 2.7; P =.001). Conversely, no correlation was observed between the pathologic score and the presence of a ramp lesion (odds ratio = 0.88; P =.578). Conclusion: The prevalence of pathologic findings in the direct arm of the SM tendon insertion was high in the acutely injured cohort with ACL rupture and is correlated with the presence of BB at the posteromedial tibial plateau. The main hypothesis formulated for the study was confirmed. [ABSTRACT FROM AUTHOR]

Background: Nonoperative management of proximal semimembranosus injuries is associated with prolonged periods of convalescence and high risk of recurrence. To our knowledge, the outcomes of acute surgical repair for complete, nonavulsion proximal semimembranosus injuries have not been previously reported. Hypothesis: Acute surgical repair of complete, nonavulsion proximal semimembranosus injuries enables early return to sporting activity with low risk of recurrence. Study Design: Case series: Level of evidence, 4. Methods: This prospective single-surgeon study included 20 professional athletes undergoing acute primary surgical repair of complete, nonavulsion proximal semimembranosus injuries confirmed on preoperative magnetic resonance imaging. All study patients underwent a standardized postoperative rehabilitation program. Predefined outcomes were recorded at regular intervals after surgery. Mean follow-up time was 27.6 months (range, 24.0-34.6 months) from date of surgery. Results: Of the 20 patients, 19 (95%) returned to their preinjury level of sporting activity. Mean ± SD time from surgical repair to full sporting activity was 11.9 ± 5.7 weeks. No patients had recurrence of the primary injury. At 3 months after surgery, patients had improved mean passive straight leg raise (71.5° ± 5.9° vs 31.1° ± 7.2°; P <.001); increased mean isometric hamstring muscle strength at 0° (83.8% ± 5.9% vs 48.4% ± 8.3%; P <.001), 15° (77.6% ± 6.0% vs 52.3% ± 14.7%; P <.001), and 45° (88.6% ± 5.4% vs 66.7% ± 13.1%; P <.001); higher mean lower extremity functional scores (64.8 ± 4.6 vs 34.4 ± 5.1; P <.001); and improved Marx activity rating scores (10.7 ± 1.6 vs 5.5 ± 2.0; P <.001) as compared with preoperative values. High patient satisfaction and functional outcome scores were maintained at 1 and 2 years after surgery. Conclusion: Acute surgical repair of complete, nonavulsion proximal semimembranosus injuries is associated with high patient satisfaction, increased muscle strength, improved functional outcome scores, and high return to preinjury level of sporting activity with low risk of recurrence at short-term follow-up. [ABSTRACT FROM AUTHOR]

We aimed to compare dynamic exercise performance between hip extension exercises with different knee angles and between knee flexion exercises with different hip angles, and to investigate the recruitment pattern of the hamstrings in each exercise. Seven men performed 4 isokinetic exercises (3 maximal concentric contractions at 30°/s (peak torque) and 30 maximal concentric contractions at 180°/s (total work)): hip extension with the knee fully extended (HEke) and with the knee flexed at 90° (HEkf) and knee flexion with the hip fully extended (KFhe) and with the hip flexed at 90° (KFhf). The recruitment pattern of the hamstrings was evaluated in each exercise using magnetic resonance imaging (T2 calculation). The HEke condition showed significantly greater peak torque than the HEkf condition (p < 0.05). The KFhf condition had significantly greater peak torque and total work values than the KFhe condition (p < 0.05). Although the biceps femoris long head, semitendinosus, and semimembranosus had significantly increased post-exercise T2 values in the HEke (p < 0.05), KFhe, and KFhf conditions (p < 0.01), the T2 increase values were significantly greater under the KFhf than the HEke condition (p < 0.05). The semitendinosus showed a significantly greater T2 increase value than other muscles under both KFhe and KFhf conditions (p < 0.05). Performance of hip extension and knee flexion exercises increases when the hamstring muscles are in a lengthened condition. The hamstring muscles (particularly the semitendinosus) are more involved in knee flexion than in hip extension. [ABSTRACT FROM AUTHOR]

Muscle injuries are the most common injuries in sports, with hamstring injuries accounting for 29% of all injuries in athletes. These injuries lead to prolonged impairment and have a reinjury risk of 12% to 31%. They range from mild muscle damage without loss of structural integrity to complete muscle tearing with fiber disruption. Novel MRI scores are increasingly being used and allow a more precise prediction of return to sport. In this article, the authors review the history, mechanisms of injury, and classification systems for hamstring injuries as well as present the latest evidence related to the management of hamstring injuries, including intramuscular and both proximal and distal insertional injuries. Indications for surgical treatment of certain proximal and distal avulsions, biological augmentation to the nonoperative treatment of midsubstance injuries, and advances in risk reduction and injury prevention are discussed. [ABSTRACT FROM PUBLISHER]

Hamstring injuries in sport can be debilitating. The anatomical complexity of this muscle makes uniform assessment of injury epidemiology difficult and insures that post-injury management strategies must be individually focused. This article reviews the anatomy of the hamstring, its role in athletic movement, common mechanisms of injury, and management guidelines with the goal of return into sporting activity in mind. [ABSTRACT FROM AUTHOR]

The hamstring muscles, located in the posterior thigh, include the biceps femoris, the semimembranosus, and the semitendinosus. The proximal portions of the hamstring muscles are subject to a variety of injuries and pathology. Many of these entities affect the origin of the hamstrings, including the tendinous enthesis, the underlying ischial tuberosity, and the surrounding tissues. Tendinosis and small partial tears at the origin are the result of chronic attrition. They may be accompanied by bursitis or hamstring syndrome. Apophysitis occurs in teenagers prior to complete fusion of the ischial apophysis and results from repeated traction injuries on the apophysis without discrete displacement. Abrupt injury at the origin from forced flexion of the hip results in osseous avulsions of the apophysis in teenagers and proximal tendon ruptures in adults. Other entities affect the muscles distal to the tendon origins. These injuries include strains and partial tears of the musculotendinous junction from acute indirect trauma, delayed onset muscle soreness from overuse of the muscle group without discrete remembered injury, and contusions and myositis ossificans from direct blunt impact. The imaging features of these injuries and pathology are fairly specific and diagnostic, with the exception of some cases of myositis ossificans and chronic ischial avulsions. [ABSTRACT FROM AUTHOR]

Abstract: Tendon orientations in knee models are often taken from cadaver studies. The aim of this study was to investigate the effect of muscle activation on tendon orientation in vivo. Magnetic resonance imaging (MRI) images of the knee were made during relaxation and isometric knee extensions and flexions with 0°, 15° and 30° of knee joint flexion. For six tendons, the orientation angles in sagittal and frontal plane were calculated. In the sagittal plane, muscle activation pulled the patellar tendon to a more vertical orientation and the semitendinosus and sartorius tendons to a more posterior orientation. In the frontal plane, the semitendinosus had a less lateral orientation, the biceps femoris a more medial orientation and the patellar tendon less medial orientation in loaded compared to unloaded conditions. The knee joint angle also influenced the tendon orientations. In the sagittal plane, the patellar tendon had a more anterior orientation near full extension and the biceps femoris had an anterior orientation with 0° and 15° flexions and neutral with 30° flexions. Within 0° to 30° of flexion, the biceps femoris cannot produce a posterior shear force and the anterior angle of the patellar tendon is always larger than the hamstring tendons. Therefore, co-contraction of the hamstring and quadriceps is unlikely to reduce anterior shear forces in knee angles up to 30°. Finally, inter-individual variation in tendon angles was large. This suggests that the amount of shear force produced and the potential to counteract shear forces by co-contraction is subject-specific. [Copyright &y& Elsevier]

Background: The presentation of patients with knee injuries which can have a significant impact on their ability to work and perform activities of daily living is constantly rising. The posterolateral corner of the knee has a complex anatomy of muscles, tendons, and ligaments, with huge variation in the population. The fabella is one such structure, found in the posterolateral corner of the knee, which can serve as a common origin point of various ligaments.Case Report: We present a case report of a 53-year-old white man who presented with atraumatic, posterior knee pain and was found to have a congenital, anomalous band originating from the fabella, causing semimembranosus impingement. This was diagnosed with magnetic resonance imaging; he underwent division of the anomalous band, which resulted in complete resolution of his symptoms.Conclusion: We propose that patients who present with posterior knee pain, without any history of trauma, and have no abnormalities on plain radiographs, should undergo magnetic resonance imaging of their knees. This will help in assessing the ligament complex in the posterior compartment of the knee, and exclude impingement of the semimembranosus as an, albeit rare, cause of posteromedial knee pain. [ABSTRACT FROM AUTHOR]