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Background: The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint to lateral patellar translation and is often disrupted by lateral patellar dislocation. Surgical management for recurrent patellar instability focuses on restoring the MPFL function with repair or reconstruction techniques. Recent studies have favored reconstruction over repair; however, long-term comparative studies are limited., Purpose: To compare long-term clinical outcomes, complications, and recurrence rates of isolated MPFL reconstruction and MPFL repair for recurrent lateral patellar instability., Study Design: Cohort study; Level of evidence, 3., Methods: A total of 55 patients (n = 58 knees) with recurrent lateral patellar instability were treated between 2005 and 2012 with either MPFL repair or MPFL reconstruction. The exclusion criteria were previous or concomitant tibial tubercle osteotomy or trochleoplasty and follow-up of <8 years. Pre- and postoperative descriptive, surgical, imaging, and clinical data were recorded for each patient., Results: MPFL repair was performed on 26 patients (n = 29 knees; 14 women, 15 men), with a mean age of 18.4 years. MPFL reconstruction was performed on 29 patients (n = 29 knees; 18 women, 11 men), with a mean age of 18.2 years. At a mean follow-up of 12 years (range, 8.3-18.9 years), the reconstruction group had a significantly lower rate of recurrent dislocation compared with the repair group (14% vs 41%; P = .019). There were no differences in the number of preoperative dislocations or tibial tubercle-trochlear groove distance. The reconstruction group had significantly more time from initial injury to surgery compared with the repair group (median, 1460 days vs 627 days; P = .007). There were no differences in postoperative Tegner, Lysholm, or Kujala scores at the final follow-up. In addition, no statistically significant differences were detected in return to sport (RTS) rates (repair [81%] vs reconstruction [75%]; P = .610) or reoperation rates for recurrent instability (repair [21%] vs reconstruction [7%]; P = .13)., Conclusion: MPFL repair resulted in a nearly 3-fold higher rate of recurrent patellar dislocation (41% vs 14%) at the long-term follow-up compared with MPFL reconstruction. Given this disparate rate, the authors recommend MPFL reconstruction over repair because of the lower failure rate and similar, if not superior, clinical outcomes and RTS., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: C.L.C. has received research support from Major League Baseball; education payments from Arthrex; consulting fees from Arthrex; nonconsulting fees from Arthrex, Zimmer Biomet Holdings, and Gemini Mountain Medical; and royalties from Arthrex. D.B.F.S. has received research support from JRF Ortho and consulting fees from NewClip. A.J.K. has received research support from Aesculap, Arthrex, Arthritis Foundation, Ceterix, and Histogenics; grants from DJO and Exactech; consulting fees from Arthrex, JRF Ortho, Vericel, and Responsive Arthroscopy; nonconsulting fees from Arthrex; royalties from Arthrex, JRF Ortho, and Responsive Arthroscopy; honoraria from MTF Biologics, JRF Ortho, and Responsive Arthroscopy; and hospitality payments from Gemini Mountain Medical and Smith & Nephew and serves on the medical board of trustees for MTF Biologics. M.J.S. has received research support from Stryker; education payments from Arthrex; consulting fees from Arthrex; nonconsulting fees from Arthrex; and royalties from Arthrex. 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. Ethical approval for this study was obtained from the Mayo Clinic (ref No. PR15-000601-09)., (© The Author(s) 2024.)

Orthobiologic therapies show significant promise to improve outcomes for patients with musculoskeletal pathology. There are considerable research efforts to develop strategies that seek to modulate the biological environment to promote tissue regeneration and healing and/or provide symptomatic relief. However, the regulatory pathways overseeing the clinical translation of these therapies are complex, with considerable worldwide variation. The introduction of novel biologic treatments into clinical practice raises several ethical dilemmas. In this review, we describe the process for seeking approval for biologic therapies in the United States, Europe, and Japan. We highlight a number of ethical issues raised by the clinical translation of these treatments, including the design of clinical trials, monitoring outcomes, biobanking, "off-label" use, engagement with the public, marketing of unproven therapies, and scientific integrity., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This work was supported by the Orthoregeneration Network. J.C. has received education payments from Arthrex and Smith & Nephew; consulting fees from DePuy, Linvatec, and Smith & Nephew; speaking fees from Linvatec; and hospitality payments from Medical Device Business Services, Medwest, and Stryker. N.S.P. has received research support from Zimmer Biomet Holdings and RegenLab. R.M.F. has received grant support from Arthrex, education payments from Arthrex and Smith & Nephew, nonconsulting fees from Arthrex, and hospitality payments from Joint Restoration Foundation. J.H. has received education payments from Gemini Mountain. B.M. has received speaking fees from Arthrex and consulting fees from Arthrex, Biomarin Pharmaceutical, DePuy, and Exactech. J.L.D. has received grant support from Terumo BCT; consulting fees from Arthrex, Bioventus, DePuy, RTI Surgical, and Zimmer; and nonconsulting fees from Arthrex. 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) 2022.)

Background: Some surgeons are now considering fixation of traumatic chondral-only fragments in juvenile knees, but few data remain to guide treatment., Purpose: To determine if surgical fixation of chondral-only fragments in the juvenile knee results in an adequate healing response with successful imaging and clinical outcomes., Study Design: Case series; Level of evidence, 4., Methods: Data were collected on 16 skeletally immature patients treated with fixation of chondral-only fragments with a minimum 1-year follow-up. Patients were selected by the operating surgeons based on the quality and size of the chondral fragment. Demographic data, lesion characteristics, surgical procedure details, complications, and postoperative imaging were assessed. Validated outcome measures were collected pre- and postoperatively and included the following scores: International Knee Documentation Committee (IKDC), Marx Activity Scale, Knee injury and Osteoarthritis Outcome Score (KOOS), Hospital for Special Surgery Pediatric Functional Activity-Brief Scale (HSS Pedi-FABS), Patient-Reported Outcomes Measurement Information System (PROMIS)-Physical Health and PROMIS-Psychological Health, and Tegner., Results: The mean age of our patient cohort was 14.9 years. The mean size of the repaired defects measured 3.2 cm 2 . Injury sites included the patella (n = 1), medial femoral condyle (n = 3), trochlea (n = 4), and lateral femoral condyle (n = 8). Within the mean follow-up time of 42.3 months (range, 15-145), there was 1 clinical failure with loosening of the chondral fragment and the need for reoperation. At a mean follow-up of 3.5 years, the mean (interquartile range) patient-reported outcome scores were as follows: IKDC, 95.2 (94.3-100); Marx Activity Scale, 11.5 (11.5-16); KOOS, 95.81 (93.5-95.81); HSS Pedi-FABS, 16.94 (11.5-26); PROMIS-Physical Health, 93.75% (90%-100%); PROMIS-Psychological Health, 90% (88.75%-100%); and Tegner, 5.69 (4.75-7). All patients who were engaged in sports before injury returned to the same or higher level of competition with the exception of 1 patient., Conclusion: Primary repair of chondral-only injuries with internal fixation can be a successful treatment option in selected patients. Clinical and imaging results at final follow-up suggest that reintegration of the cartilage fragment is achievable and leads to excellent clinical function and a high return-to-sports rate., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: Support was received from the Foderaro-Quattrone Musculoskeletal-Orthopaedic Surgery Research Innovation Fund. This study was also partially funded by the Deutsche Forschungsgemeinschaft (grant 466023693) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases for the Musculoskeletal Research Training Program (grant T32AR56950). A.J.K. has received grant support from DJO; consulting fees from Arthrex, Joint Restoration Foundation, and Responsive Arthroscopy; speaking fees from Arthrex; honoraria from Vericel and Joint Restoration Foundation; and royalties from Arthrex and Responsive Arthroscopy; he is also a board member for the Musculoskeletal Transplant Foundation. M.J.S. has received education payments from Elite Orthopedics; consulting fees, speaking fees, and royalties from Arthrex; and hospitality payments from Stryker. T.A.M. has received consulting fees from Medtronic, OrthoPediatrics, and Zimmer Biomet. D.B.F.S. has received research funding from Arthrex. 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) 2022.)

Background: Little is known about the benefits and outcomes of meniscal repair in patients older than 60 years., Purpose: To (1) report the clinical and radiographic outcomes of meniscal repair in patients aged ≥60 years and compare them with matched patients who underwent meniscectomy and (2) identify procedural failures., Study Design: Cohort study; Level of evidence, 2., Methods: We included 32 knees in 32 patients aged ≥60 years (20 female, 12 male; mean age, 64.5 ± 4.6 years) who underwent meniscal repair surgery at a single medical institution between 2010 and 2020. Patients were matched according to age, sex, body mass index, and meniscal tear type with a comparison cohort who underwent meniscectomy (n = 49 patients [49 knees]; 32 female, 17 male). For all patients, demographic information, clinical history, physical examination findings, treatment details, and radiographic images were reviewed and analyzed. At final follow-up (mean, 42.2 months; range, 13-128 months), patients completed the 2000 International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Knee injury and Osteoarthritis Outcome Score (KOOS), and Lysholm score. Clinical failure was defined as revision surgery and/or progression to total knee arthroplasty (TKA). A matched-pairs t test was used to analyze differences between the 2 treatment groups, and Kaplan-Meier analysis was used to determine the rates of knee osteoarthritis and progression to TKA., Results: The majority of patients had a medial meniscal tear (72.8%), whereas the lateral meniscus was torn in 27.2% of cases. Most tears were located in the meniscal root (56.8%), followed by the posterior horn (34.6%) and midbody (8.6%). At final follow-up, all outcome scores were higher in the repair group compared with the meniscectomy group (IKDC, 78.9 ± 13.4 vs 56.0 ± 15.4; KOOS, 86.6 ± 11.9 vs 61.7 ± 16.2; Lysholm, 88.3 ± 13.3 vs 68.7 ± 15.2, respectively; P < .001 for all). Clinical failure was observed in 22% of patients in the repair group., Conclusion: All clinical outcome scores were higher in the meniscal repair group compared with the matched meniscectomy group at final follow-up. The clinical failure rate of the repair group was 22%. These findings support meniscal repair in selected patients aged ≥60 years., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: The authors acknowledge support from the Foderaro-Quattrone Musculoskeletal-Orthopaedic Surgery Research Innovation Fund. This study was partially funded by the Deutsche Forschungsgemeinschaft (grant No. 466023693 to M.H.) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases for the Musculoskeletal Research Training Program (T32AR56950). N.I.K. has received hospitality payments from Encore Medical. M.J.S. has received research support from Stryker and consulting fees, nonconsulting fees, and royalties from Arthrex. A.J.K. has received grant support from DJO; consulting fees from Arthrex, the Joint Restoration Foundation, and Responsive Arthroscopy; speaking fees from Arthrex; royalties from Arthrex and Responsive Arthroscopy; and honoraria from Vericel and the Joint Restoration Foundation; he serves on the medical board of trustees for the Musculoskeletal Transplant Foundation. D.B.F.S. has received consulting fees from Smith & Nephew. 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) 2022.)

Interest and research in biologic approaches for tissue healing are exponentially growing for a variety of musculoskeletal conditions. The recent hype concerning musculoskeletal biological therapies (including viscosupplementation, platelet-rich plasma, and cellular therapies, or "stem cells") is driven by several factors, including demand by patients promising regenerative evidence supported by substantial basic and translational work, as well as commercial endeavors that complicate the scientific and lay understanding of biological therapy outcomes. While significant improvements have been made in the field, further basic and preclinical research and well-designed randomized clinical trials are needed to better elucidate the optimal indications, processing techniques, delivery, and outcome assessment. Furthermore, biologic treatments may have potential devastating complications when proper methods or techniques are ignored. For these reasons, an association comprising several scientific societies, named the Biologic Association (BA), was created to foster coordinated efforts and speak with a unified voice, advocating for the responsible use of biologics in the musculoskeletal environment in clinical practice, spearheading the development of standards for treatment and outcomes assessment, and reporting on the safety and efficacy of biologic interventions. This article will introduce the BA and its purpose, provide a summary of the 2020 first annual Biologic Association Summit, and outline the future strategic plan for the BA., Competing Interests: One or more of the authors has declared a potential conflict of interest or source of funding: see supplemental material for details. 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.)

Background: It is unknown whether the treatment effects of partial meniscectomy and physical therapy differ when focusing on activities most valued by patients with degenerative meniscal tears., Purpose: To compare partial meniscectomy with physical therapy in patients with a degenerative meniscal tear, focusing on patients' most important functional limitations as the outcome., Study Design: Randomized controlled trial; Level of evidence, 1., Methods: This study is part of the Cost-effectiveness of Early Surgery versus Conservative Treatment with Optional Delayed Meniscectomy for Patients over 45 years with non-obstructive meniscal tears (ESCAPE) trial, a multicenter noninferiority randomized controlled trial conducted in 9 orthopaedic hospital departments in the Netherlands. The ESCAPE trial included 321 patients aged between 45 and 70 years with a symptomatic, magnetic resonance imaging-confirmed meniscal tear. Exclusion criteria were severe osteoarthritis, body mass index >35 kg/m 2 , locking of the knee, and prior knee surgery or knee instability due to an anterior or posterior cruciate ligament rupture. This study compared partial meniscectomy with physical therapy consisting of a supervised incremental exercise protocol of 16 sessions over 8 weeks. The main outcome measure was the Dutch-language equivalent of the Patient-Specific Functional Scale (PSFS), a secondary outcome measure of the ESCAPE trial. We used crude and adjusted linear mixed-model analyses to reveal the between-group differences over 24 months. We calculated the minimal important change for the PSFS using an anchor-based method., Results: After 24 months, 286 patients completed the follow-up. The partial meniscectomy group (n = 139) improved on the PSFS by a mean of 4.8 ± 2.6 points (from 6.8 ± 1.9 to 2.0 ± 2.2), and the physical therapy group (n = 147) improved by a mean of 4.0 ± 3.1 points (from 6.7 ± 2.0 to 2.7 ± 2.5). The crude overall between-group difference showed a -0.6-point difference (95% CI, -1.0 to -0.2; P = .004) in favor of the partial meniscectomy group. This improvement was statistically significant but not clinically meaningful, as the calculated minimal important change was 2.5 points on an 11-point scale., Conclusion: Both interventions were associated with a clinically meaningful improvement regarding patients' most important functional limitations. Although partial meniscectomy was associated with a statistically larger improvement at some follow-up time points, the difference compared with physical therapy was small and clinically not meaningful at any follow-up time point., Registration: NCT01850719 (ClinicalTrials.gov identifier) and NTR3908 (the Netherlands Trial Register)., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: Funding for the ESCAPE trial was provided by the Netherlands Organization for Health Research and Development (ZonMw; grant 837002009), Zilveren Kruis (grant Z436), and the foundation of medical research of OLVG (grant 15u.025). The funders had no role in designing and conducting this study; the collection, management, analysis, and interpretation of the data; the preparation, review, and approval of the manuscript; or the decision to submit the manuscript for publication. 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) 2020.)

Background: Anterior cruciate ligament (ACL) tear and meniscal injury often co-occur. The protective effect of early ACL reconstruction (ACLR) on meniscal injury and its repair is not clear. Critical literature review can support or change clinical strategies and identify gaps in the available evidence., Purpose: To assess the protective effect of ACLR on the meniscus and provide clinical guidelines for managing ACL tears and subsequent meniscal injury. We aimed to answer the following questions: (1) Does ACLR protect the meniscus from subsequent injury? (2) Does early ACLR reduce secondary meniscal injury compared with delayed ACLR? (3) Does ACLR protect the repaired meniscus?, Study Design: Systematic review; Level of evidence, 4., Methods: A systematic review was performed through use of MEDLINE and Embase electronic databases according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Search terms included ACL , reconstruction , and meniscus . Studies describing primary ACLR and nonoperative treatment in adult patients were included, as well as studies indicating timing of ACLR. The included articles were assessed individually for risk of bias through use of the modified Cochrane Risk of Bias and MINORS (Methodological Index for Nonrandomized Studies) tools., Results: One level 2 randomized controlled trial and several level 3 and 4 studies indicated a protective effect of ACLR on meniscal injury compared with nonoperative treatment. There was weak (level 3) evidence of the protective effect of early ACLR on the meniscus. Meniscal repair failure was less frequent in patients with ACL reconstruction than in patients with ACL deficiency (level 4)., Conclusion: The evidence collected in this review suggests a protective effect of ACLR for subsequent meniscal injury (level 2 evidence). ACLR should be performed within 3 months of injury (level 3 evidence). Meniscal injury requiring surgical repair in the ACL-deficient knee should be treated with repair accompanied by ACLR (level 3 evidence). The paucity of level 2 studies prevents the formation of guidelines based on level 1 evidence. There is a strong clinical need for randomized or prospective trials to provide guidelines on timing of ACLR and meniscal repair., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This research was supported by the Dutch Arthritis Foundation (LLP-12 and LLP-22). L.A.V. is employed by CO.DON AG. A.J.K. has received research support from Aesculap/B.Braun, Ceterix, Exactech, Gemini Medical, and Histogenics; consulting fees from Arthrex, JRF Ortho, and Vericel; speaking fees from Arthrex; royalties from Arthrex; and honoraria from Vericel; is a board or committee member for the Musculoskeletal Transplant Foundation; and has stock/stock options in Responsive Arthroscopy. D.B.F.S. has received research support from JRF Ortho. 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) 2020.)

Background: The preoperative assessment of cartilage lesions is critical to surgical planning and decision making. The accurate radiographic determination of acetabular cartilage damage has remained elusive for modern imaging modalities, including magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA). While risk factors have been individually described, no multivariable system exists for predicting high-grade cartilage damage., Purpose: To determine the preoperative predictors of grade 3 to 4 acetabular labrum articular disruption (ALAD) lesions., Study Design: Case-control study; Level of evidence, 3. Cohort study (diagnosis); Level of evidence, 1., Methods: Retrievable radiographs were reviewed from primary hip arthroscopic procedures performed at 2 high-volume institutions between December 2007 and April 2017. The predictive value of demographic and radiographic factors for the intraoperative documentation of ALAD grade 3 to 4 damage was analyzed and entered into a multivariable model, and a statistically guided scoring system for the damage risk was created using the Akaike information criterion. The scoring system was then prospectively validated on 167 patients who underwent primary hip arthroscopy between April 2017 and February 2018., Results: A total of 652 primary hip arthroscopic procedures in 614 patients (390 female, 224 male; mean age, 33.2 ± 12.5 years; mean body mass index, 26.9 ± 5.5 kg/m 2 ) from 2007 to 2017 were analyzed. Male sex (odds ratio [OR], 3.11; P < .01), age ≥35 years (OR, 1.96; P < .01), cam morphology (alpha angle >55°) (OR, 2.96; P < .01), and Tönnis grade 1 to 2 (grade 1: OR, 4.14; P < .01, and grade 2: OR, 9.29; P < .01) were univariate risk factors for intraoperatively documented high-grade damage. A multivariable scoring system, the Rapidly Assessed Predictor of Intraoperative Damage (RAPID) score (0-5 points), was generated based on sex, Tönnis grade, and cam morphology. Patients with increasing RAPID scores had an increasing risk of damage, with a 10.5% risk for those with 0 points and an 88.0% risk for those with 5 points ( P < .01). The area under the curve was 0.75 for the study group and 0.76 for the validation group ( P = .94)., Conclusion: While preoperative MRI has diagnostic value for hip arthroscopic surgery, the RAPID score provides added benefit as a readily employable, in-clinic system for predicting high-grade cartilage damage. The discriminatory value of the RAPID score compares favorably with previous MRI and MRA studies. This information will help the clinician and patient plan for high-grade damage and identify potential targets for cartilage treatment., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: M.H. has received hospitality payments from DePuy. D.E.H. has received educational support from Arthrex and Smith & Nephew and hospitality payments from Desert Mountain Medical and Stryker. D.B.F.S. is a paid speaker/presenter for Smith & Nephew and is a paid consultant for Smith & Nephew, Genzyme, and TiGenix. B.A.L. receives royalties from Arthrex and VOT Systems, is a paid consultant for Arthrex, and is a paid speaker/presenter for the Canadian Orthopaedic Association and Smith & Nephew. A.J.K. receives research support from Aesculap/B. Braun, the Arthritis Foundation, Ceterix, and Histogenics; receives royalties from Arthrex; is a paid consultant for Arthrex, Vericel, and DePuy; and has received honoraria from Vericel and the Musculoskeletal Transplant Foundation. 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.

Background: As the number of cartilage restoration procedures is increasing, so is the number of revision procedures. However, there remains limited information on the reasons for failure of primary cartilage restoration procedures., Purpose: To determine the common modes of failure in primary cartilage restoration procedures to improve surgical decision making and patient outcomes., Study Design: Case series; Level of evidence, 4., Methods: Patients who presented for revision after failed cartilage repair surgery were evaluated for factors contributing to failure of the primary procedure. All revision cases performed by a single surgeon at a tertiary center for failed cartilage restoration over a 6-year time frame were identified. In all cases, the medical records, preoperative radiographs, and magnetic resonance imaging scans were reviewed by 2 experienced cartilage surgeons. The cause for failure was categorized as malalignment, meniscal deficiency, graft or biologic failure, or instability. Univariate and descriptive statistics regarding patient demographics, index procedure, lesion location and size, and mechanism of failure were analyzed., Results: A total of 59 cases in 53 patients (32 male, 21 female) met the inclusion criteria. The mean patient age at the time of revision was 27.6 years, and the mean body mass index was 28.4 kg/m 2 . Failed index surgical procedures included 35 microfractures (59%), 12 osteochondral allograft transplantations (20%), 10 osteochondral autograft transfers (17%), 2 nonviable osteochondral allografts (3%), and 2 particulated juvenile chondral allografts (3%). The mean lesion size was 4.4 cm 2 . Reasons for failure included 33 cases with untreated malalignment (56%), 16 with graft failure (27%), 11 with untreated meniscal deficiency (19%), and 3 with untreated instability (5%); 4 cases demonstrated multiple reasons for failure., Conclusion: The most commonly recognized reason for failure was untreated malalignment. While biologic and graft failures will occur, the majority of failures were attributed to untreated background factors such as malalignment, meniscal deficiency, and instability. The stepwise approach of considering and addressing alignment, meniscal volume, and stability remains essential in cartilage restoration surgery., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: A.J.K. receives research support from Aesculap/B. Braun, the Arthritis Foundation, Ceterix, and Histogenics; is a paid consultant for Arthrex, Vericel, and DePuy Orthopaedics; receives royalties from Arthrex; has received honoraria from the Musculoskeletal Transplant Foundation; and has received hospitality payments from Arthrex and the Musculoskeletal Transplant Foundation. M.J.S. is a paid consultant for Arthrex, receives royalties from Arthrex, receives research support from Stryker, and has received hospitality payments from Arthrex. D.B.F.S. receives research support from Arthrex, Ivy Sports Medicine, and Smith & Nephew and is a paid consultant for Cartiheal, Smith & Nephew, and Vericel.

Background: Lateral meniscus posterior root tears (LMPRTs), if left untreated, can cause devastating effects to the knee, with rapid articular cartilage degeneration and loss of the meniscus as a secondary stabilizer. Detection and surgical repair of these defects have been linked to favorable outcomes, but preoperative identification of LMPRTs continues to be challenging., Purpose: To determine the rate of LMPRTs diagnosed preoperatively on magnetic resonance imaging (MRI) in a consecutive series of arthroscopically confirmed LMPRTs., Study Design: Case series; Level of evidence, 4., Methods: A retrospective cohort of 45 consecutive patients with arthroscopically confirmed LMPRTs between 2010 and 2017 were included in this study. The preoperative MRI report for each patient was evaluated and compared with intraoperative findings. Each preoperative MRI study was then reviewed by 2 fellowship-trained musculoskeletal radiologists who worked in consensus., Results: A total of 45 patients (32 males, 13 females) with arthroscopically confirmed LMPRTs and a mean age of 27 years (range, 14-54 years) were included in the study. Only 15 of 45 LMPRTs (33%) were initially diagnosed on preoperative MRI. Past or concurrent anterior cruciate ligament (ACL) reconstruction was present in 37 of 45 cases (82%). Upon retrospective review, 15 of the 30 missed LMPRTs were "clearly evident," 12 "subtly evident," and 3 "occult" (unavoidably missed). There were no significant differences in the rate of LMPRT diagnosis based on history of prior knee surgery, meniscus extrusion, or tearing of the meniscofemoral ligament., Conclusion: Despite improved identification of other meniscus tear patterns on MRI, a high percentage of LMPRTs were still missed. In the setting of previous ACL reconstruction, if the root cannot be confidently identified, the MRI interpretation should indicate that "the root is poorly visualized" to alert the surgeon to thoroughly evaluate this structure. The surgeon should maintain a high index of suspicion and carefully probe the posterior root of the lateral meniscus at the time of arthroscopy, especially in cases of ACL injury., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: A.J.K. receives research support from Aesculap/B. Braun, the Arthritis Foundation, Ceterix, and Histogenics; is a paid consultant for Arthrex and Vericel; and is on the board of the Musculoskeletal Transplant Foundation. D.B.F.S. receives research support from Arthrex, Ivy Sports, and Smith & Nephew and is a paid consultant for Cartiheal, Smith & Nephew, and Vericel. B.A.L. receives royalties from Arthrex; is paid consultant for Arthrex and Smith & Nephew; and receives research support from Arthrex, Biomet, Smith & Nephew, and Stryker. M.J.S. is a paid consultant for Arthrex, receives royalties from Arthrex, and receives research support from Stryker.

Background: Meniscus damage can be caused by trauma or degeneration and is therefore common among patients of all ages. Repair or regeneration of the menisci could be of great importance not only for pain relief or regaining function but also to prevent degenerative disease and osteoarthritis. Current treatment does not offer consistent long-term improvement. Although preclinical research focusing on augmentation of meniscal tear repair and regeneration after meniscectomy is encouraging, clinical translation remains difficult., Purpose: To systematically evaluate the literature on in vivo meniscus regeneration and explore the optimal cell sources and conditions for clinical translation. We aimed at thorough evaluation of current evidence as well as clarifying the challenges for future preclinical and clinical studies., Study Design: Systematic review., Methods: A search was conducted using the electronic databases of MEDLINE, Embase, and the Cochrane Collaboration. Search terms included meniscus , regeneration , and cell-based ., Results: After screening 81 articles based on title and abstract, 51 articles on in vivo meniscus regeneration could be included; 2 additional articles were identified from the references. Repair and regeneration of the meniscus has been described by intra-articular injection of multipotent mesenchymal stromal (stem) cells from adipose tissue, bone marrow, synovium, or meniscus or the use of these cell types in combination with implantable or injectable scaffolds. The use of fibrochondrocytes, chondrocytes, and transfected myoblasts for meniscus repair and regeneration is limited to the combination with different scaffolds. The comparative in vitro and in vivo studies mentioned in this review indicate that the use of allogeneic cells is as successful as the use of autologous cells. In addition, the implantation or injection of cell-seeded scaffolds increased tissue regeneration and led to better structural organization compared with scaffold implantation or injection of a scaffold alone. None of the studies mentioned in this review compare the effectiveness of different (cell-seeded) scaffolds., Conclusion: There is heterogeneity in animal models, cell types, and scaffolds used, and limited comparative studies are available. The comparative in vivo research that is currently available is insufficient to draw strong conclusions as to which cell type is the most promising. However, there is a vast amount of in vivo research on the use of different types of multipotent mesenchymal stromal (stem) cells in different experimental settings, and good results are reported in terms of tissue formation. None of these studies compare the effectiveness of different cell-scaffold combinations, making it hard to conclude which scaffold has the greatest potential., Competing Interests: The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.

Background: There is a need for tools to predict the chondrogenic potency of autologous cells for cartilage repair., Purpose: To evaluate previously proposed chondrogenic biomarkers and to identify new biomarkers in the chondrocyte transcriptome capable of predicting clinical success or failure after autologous chondrocyte implantation., Study Design: Controlled laboratory study and case-control study; Level of evidence, 3., Methods: Five patients with clinical improvement after autologous chondrocyte implantation and 5 patients with graft failures 3 years after implantation were included. Surplus chondrocytes from the transplantation were frozen for each patient. Each chondrocyte sample was subsequently thawed at the same time point and cultured for 1 cell doubling, prior to RNA purification and global microarray analysis. The expression profiles of a set of predefined marker genes (ie, collagen type II α1 [COL2A1], bone morphogenic protein 2 [BMP2], fibroblast growth factor receptor 3 [FGFR3], aggrecan [ACAN], CD44, and activin receptor-like kinase receptor 1 [ACVRL1]) were also evaluated., Results: No significant difference in expression of the predefined marker set was observed between the success and failure groups. Thirty-nine genes were found to be induced, and 38 genes were found to be repressed between the 2 groups prior to autologous chondrocyte implantation, which have implications for cell-regulating pathways (eg, apoptosis, interleukin signaling, and β-catenin regulation)., Conclusion: No expressional differences that predict clinical outcome could be found in the present study, which may have implications for quality control assessments of autologous chondrocyte implantation. The subtle difference in gene expression regulation found between the 2 groups may strengthen the basis for further research, aiming at reliable biomarkers and quality control for tissue engineering in cartilage repair., Clinical Relevance: The present study shows the possible limitations of using gene expression before transplantation to predict the chondrogenic and thus clinical potency of the cells. This result is especially important as the chondrogenic potential of the chondrocytes is currently part of quality control measures according to European and American legislations regarding advanced therapies.