Abstract
Background:
Medial meniscus posterior root tears (MMPRTs) have been associated with rapidly progressive cartilage degeneration when left untreated in adults. However, their clinical presentation, tear morphology, and associated cartilage pathology remain poorly characterized in pediatric and adolescent patients.
Purpose:
To identify risk factors for medial tibiofemoral compartment cartilage injury in pediatric and adolescent patients undergoing MMPRT repair, and secondarily to characterize MMPRT morphologies and skeletal maturity–associated injury patterns.
Study Design:
Case series; Level of evidence, 4.
Methods:
Patients <19 years of age who underwent a transosseous MMPRT repair between 2015 and 2025 across 5 institutions were included. Operative records were reviewed to classify MMPRT morphology using the LaPrade classification and to document concomitant ligamentous procedures. The presence, location, and severity of arthroscopically identified medial tibiofemoral compartment cartilage injuries involving the medial femoral condyle (MFC) and/or medial tibial plateau were graded using the International Cartilage Regeneration & Joint Preservation Society (ICRS) classification. Patients with and without medial compartment cartilage injury were compared, and multivariable logistic regression was used to identify risk factors associated with its presence at the time of surgery.
Results:
A total of 75 patients underwent a transosseous MMPRT repair (mean age, 15.2 ± 2.3 years), and 40% were skeletally immature. The most common MMPRT morphology was a type 5 root avulsion (55%), followed by a type 2 complete radial root tear (36%). Skeletally immature patients more frequently sustained isolated MMPRTs (60% vs 11%; P < .001), whereas skeletally mature adolescents more commonly had ligament-associated MMPRTs (89% vs 40%; P < .001). Overall, medial compartment cartilage injury was arthroscopically identified in 34 patients (45%) at the time of surgery. Most cartilage injuries involved the MFC (82%) and were classified as ICRS grade 1 (15%) or grade 2 (62%), while 24% were high-grade (ICRS grade 3 or 4). Multivariable logistic regression demonstrated that age (OR per year, 1.33; 95% CI, 1.02-1.73; P = .03) and delayed surgery (≥90 days after injury) (OR, 4.96; 95% CI, 1.6-15; P = .005) were significantly associated with medial compartment cartilage injury. The association between delayed surgery and medial compartment cartilage injury remained consistent in a sensitivity analysis incorporating concomitant ligament injury.
Conclusion:
Concomitant medial compartment cartilage injury was arthroscopically identified in 45% of pediatric and adolescent patients undergoing MMPRT repair. While most of these cartilage injuries involved the MFC and were classified as ICRS grade 2, nearly one-quarter were high-grade lesions (ICRS grade 3 or 4). Increasing age and delayed surgery (≥90 days after injury) were significantly associated with medial compartment cartilage injury. Overall, these findings underscore the potential importance of timely recognition and surgical treatment of MMPRTs in young patients.
Keywords
Over the last decade, medial meniscus posterior root tears (MMPRTs) have been increasingly recognized for their substantial biomechanical consequences and association with cartilage degeneration within the medial tibiofemoral compartment.22,31,41,42,46 In adults, MMPRTs are typically degenerative and most commonly occur in middle-aged women with an elevated body mass index (BMI). 41 Biomechanically, disruption of the posterior root attachment eliminates circumferential hoop stresses of the meniscus, resulting in extrusion, increased medial tibiofemoral contact pressures, and reduced contact area that mirror a total medial meniscectomy.1,13,15,27,31,42 Clinically, untreated or nonoperatively managed MMPRTs may precipitate the progression to advanced osteoarthritis, often culminating in an early total knee arthroplasty within months to several years.11,12,22-25,46 Given these potential consequences, early anatomic root repair is generally recommended in symptomatic adult patients without advanced osteoarthritis.5,31
In contrast, meniscus root tears are reported to be rare in the pediatric and adolescent population, comprising an estimated 2% of pediatric meniscal injuries.39,44,48 Among those reported in this population, the majority have been lateral meniscus posterior root tears associated with an anterior cruciate ligament (ACL) tear.6,48 However, far less is known about the epidemiology, injury patterns, and clinical significance of pediatric MMPRTs, where the mechanism is often traumatic rather than degenerative. In 2018, Wilson et al 48 identified <10 cumulative cases of pediatric MMPRTs described in the literature at that time, and more recent studies continue to lack cohorts with >10 patients with MMPRTs.6,18,45 While these small case series report favorable outcomes after a transosseous repair with minimal risk to the physis,6,8,45 they primarily describe isolated MMPRTs and lack comprehensive characterization of the tear morphology, associated ligament injuries, and presence or severity of concomitant cartilage damage within the medial compartment at the time of surgery.
The development of posttraumatic osteoarthritis after a meniscal injury is multifactorial and remains incompletely understood in pediatric and adolescent patients.2,33,34 Clinically, it is unknown whether the accelerated cartilage damage associated with untreated MMPRTs observed in adults may similarly occur in young patients, particularly in children who experience a delayed diagnosis or surgical intervention. A more complete understanding of these characteristics and potential risk factors associated with pediatric MMPRTs may improve early recognition, enhance surgical decision-making, and decrease the risk of long-term cartilage damage in these young patients. Therefore, the purpose of this study was to identify risk factors for medial tibiofemoral compartment cartilage injury in pediatric and adolescent patients undergoing MMPRT repair, and secondarily to characterize MMPRT morphologies and skeletal maturity–associated injury patterns.
Methods
Patient Selection and Identification
Institutional review board approvals and multicenter data-sharing agreements were obtained at each of the 5 participating institutions (Yale School of Medicine, Hospital for Special Surgery, Rush University Medical Center, Twin Cities Orthopedics, and Texas Children's Hospital). A multicenter database search was performed to identify patients <19 years of age who underwent arthroscopic meniscal repair (Current Procedural Terminology code 29882 or 29883) between 2015 and 2025 performed by 8 different orthopaedic surgeons (1 board-certified pediatric fellowship-trained surgeon (S.D.M.), 2 board-certified pediatric and sports medicine fellowship-trained surgeons (C.F., P.D.F.) and 5 board-certified sports medicine fellowship-trained surgeons (C.R.A., E.G., M.J.M., J.C., R.F.L.)). Operative reports were then screened to identify patients who underwent a transosseous root repair for an MMPRT.
Each operative note was independently reviewed by 2 authors (J.M. and J.Z.A.) to confirm that the documented arthroscopic findings met the diagnostic criteria for an MMPRT according to the LaPrade root tear classification (Figure 1). 26 Because arthroscopic image archives were not consistently available across all centers over the 10-year study period, only patients with an MMPRT who underwent a transosseous root repair technique were included to further minimize diagnostic ambiguity. In cases of disagreement between reviewers on the LaPrade classification of the MMPRTs from the operative descriptions, the senior board-certified sports medicine fellow-trained author (R.F.L.) made the final categorization.
LaPrade classification for medial meniscus posterior root tears: type 1 (partial stable tears near or at the root attachment site), type 2 (complete radial tears within 1 cm of the root attachment), type 3 (bucket-handle tear with a complete root tear), type 4 (complete complex oblique root tear), and type 5 (bony root avulsion fracture). Original figure seen in LaPrade CM, James EW, Cram TR, Feagin JA, Engebretsen L, LaPrade RF. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;43(2):363-369. doi:10.1177/0363546514559684. 26
After identifying the initial cohort of patients with MMPRTs that underwent a transosseous repair, patients were excluded if they met any of the following criteria: concomitant periarticular fractures (not including bone bruises, subchondral insufficiency fractures, or bony root avulsions); prior history of ipsilateral knee surgery, injury, or revision surgery at the time of MMPRT repair; incomplete, ambiguous, or missing surgical documentation precluding confirmation of an MMPRT; root repairs for meniscal allograft transplantation; congenital lower extremity abnormalities; diagnosis of an ipsilateral discoid meniscus; tibial eminence avulsion fractures; or tibial tubercle fractures. This investigation was performed within the Research Evaluating Pediatric ACL-Meniscus Injuries and Repair (REPAIR) multicenter research consortium.
Preoperative and Intraoperative Data Collection
For all patients who satisfied the inclusion and exclusion criteria, the following variables were collected from the medical records, including emergency department documentation, initial clinical consultation notes, and/or operative reports: age at the time of surgery, sex (male or female), BMI, BMI percentile according to sex and age, obesity status (defined as ≥95th percentile for BMI for age and sex), 7 time between the reported date of initial injury and MMPRT repair surgery (days), and mechanism of injury (categorized as contact or noncontact and sport related or non–sport related).32,36 In alignment with prior pediatric and adolescent studies, delayed surgery was defined as surgical treatment performed ≥90 days after the initial injury.2,34
Based on prior literature, skeletal maturity was determined retrospectively based on preoperative magnetic resonance imaging (MRI) and categorized as a binary variable: skeletally mature (closed distal femoral physes) or immature (open distal femoral physes). 30 Physes were considered open if a band of high signal intensity was visible on T2-weighted MRI in the expected location of the distal femoral physeal plate.30,33 The presence or absence of an arthroscopically diagnosed concomitant lateral meniscus tear at the time of surgery was recorded from the operative reports. Concomitant ligament injury was defined by a ligament(s) that underwent surgical reconstruction or repair at the time of MMPRT repair. A multiligament knee injury (MLKI) was defined by the presence of surgical reconstruction or repair of ≥2 of the following ligaments at the time of MMPRT repair: ACL, posterior cruciate ligament (PCL), lateral (fibular) collateral ligament (LCL), and/or medial collateral ligament (MCL).29,35,37,38
Assessment of Concomitant Medial Tibiofemoral Compartment Cartilage Injuries at the Time of MMPRT Repair
Each operative report was independently reviewed by 2 authors (J.M. and J.Z.A.) to determine the presence or absence of an arthroscopically identified medial tibiofemoral compartment cartilage injury involving the medial femoral condyle (MFC) and/or medial tibial plateau (MTP) at the time of MMPRT repair. Type 5 bony root avulsion fractures or soft tissue/chondral root avulsions were not considered a concomitant MTP cartilage injury in this analysis. Given the retrospective multicenter design, each surgeon used their preferred methodology for describing and diagnosing cartilage injuries. To standardize the classification among the cohort, the 2 reviewers extracted the arthroscopic descriptions and corresponding grades from each operative report and categorized the severity of medial compartment cartilage injuries according to the International Cartilage Regeneration & Joint Preservation Society (ICRS) classification: grade 0 (normal articular cartilage), grade 1 (articular cartilage with soft indentation and/or superficial fissuring), grade 2 (articular cartilage with partial-thickness fissures that extend down to <50% of cartilage depth), grade 3 (articular cartilage defects that extend down to >50% of cartilage depth to the calcified layer but not through the subchondral bone), and grade 4 (full-thickness articular cartilage lesions with exposed subchondral bone).10,19,33 The size of the cartilage injury was not evaluated due to inconsistent reporting across operative notes. Any discrepancies between reviewers regarding the location and/or ICRS grading were similarly adjudicated by the senior author (R.F.L.). Patients were subsequently stratified into 2 groups based on the presence or absence of medial compartment cartilage injury.
Statistical Analysis
Demographics and injury patterns are reported descriptively for the overall cohort. Skeletally immature (open distal femoral physis) and skeletally mature (closed distal femoral physis) patients were compared to evaluate differences in demographics and injury patterns. Differences between the groups were compared using the Mann-Whitney U test or independent-samples t test for continuous variables and the chi-square or Fisher exact test for categorical variables.
Interrater reliability for the ICRS grading of medial compartment cartilage injuries was assessed using the intraclass correlation coefficient (ICC) with a 2-way random-effects model (absolute agreement, single measures; ICC[2,1]). All medial compartment cartilage evaluations by both reviewers were included, including grade 0 findings, and grades were treated as continuous for ICC calculation. Agreement was categorized as poor (<0.50), moderate (0.50-0.74), good (0.75-0.90), or excellent (>0.90). 21
The presence, location (MFC and/or MTP), and severity (ICRS grades 1-4) of medial compartment cartilage injuries were summarized descriptively. Differences between patients with and without medial compartment cartilage injury were similarly compared using the Mann-Whitney U test or independent-samples t test for continuous variables and the chi-square or Fisher exact test for categorical variables.
Multivariable logistic regression, using Firth penalization to mitigate small-sample bias and reduce coefficient inflation, was performed to evaluate factors associated with medial compartment cartilage injury. Candidate predictors were identified a priori based on clinical relevance, and variables showing univariate associations were also evaluated. To minimize collinearity among conceptually related variables (eg, age, sex, and skeletal maturity) and to maintain an appropriate events per variable ratio (≥10 per established recommendations), only nonoverlapping predictors were retained in the multivariable model.43,47 As such, tear morphology, concomitant ligament injury, and skeletal maturity (open distal femoral physis vs closed) were not included in the primary model due to collinearity with age. The final model therefore included age (per year increase), obesity, and delayed surgery (≥90 days after injury).
Sensitivity analyses were performed to evaluate the robustness of the association between delayed surgery (≥90 days after injury) and medial compartment cartilage injury after accounting for injury severity. Concomitant ligament injury was selected as a surrogate marker of injury severity because all concomitant meniscal pathology occurred in patients with ≥1 concomitant ligament injury, whereas isolated MMPRTs without ligament injury had no additional concomitant meniscal pathology. Because concomitant ligament injury was strongly associated with age and skeletal maturity in this cohort, 2 additional Firth penalized logistic regression models were constructed. In model 1, concomitant ligament injury was substituted for age while retaining obesity and delayed surgery (≥90 days after injury). In model 2, both age and concomitant ligament injury were included with obesity and delayed surgery (≥90 days after injury).
Model performance and discrimination were assessed using the Akaike information criterion, likelihood ratio chi-square statistic, and C statistic. Linearity of the continuous predictor (age) with the logit was confirmed using the Box-Tidwell procedure. All statistical tests were 2-tailed with an α of .05. Logistic regression was performed in SAS (Version 9.4; SAS Institute), and all other analyses were performed in SPSS (Version 29; IBM).
Results
Cohort Characteristics
In total, 83 patients were initially identified, and 8 were excluded (2 MMPRTs treated during a revision surgery, 3 tibial eminence avulsion fractures, 1 discoid meniscus, and 2 with insufficient operative documentation). Therefore, 75 pediatric and adolescent patients (mean age, 15.2 ± 2.3 years) who underwent a transosseous MMPRT repair were included in the final cohort (Table 1).
Cohort Demographics and Injury Mechanisms for Pediatric and Adolescent Patients Who Underwent a Transosseous Medial Meniscus Posterior Root Tear Repair a
Data are presented as mean ± SD (range) or n (%). BMI, body mass index.
Age- and sex-adjusted percentile values. Obesity is defined as BMI ≥95th percentile.
MMPRT Morphologies and Surgically Treated Concomitant Ligament Injuries
Overall, type 5 root avulsions were the most common MMPRT morphology (55%), followed by type 2 complete radial root tears (36%), type 4 complete complex oblique tears (8%), and type 3 bucket-handle–associated root tears (1%). Among the type 5 root avulsions, 88% were complete soft tissue/chondral root avulsions, while 12% were bony root avulsion fractures (Figure 2, Table 2).
(A) Arthroscopic image of a right knee viewing the medial tibiofemoral compartment from the anterolateral portal with the probe introduced through the anteromedial portal, demonstrating a type 5 medial meniscus (MM) posterior soft tissue/chondral root avulsion (arrow) in an 11-year-old skeletally immature boy undergoing an isolated MM posterior root repair. A small amount of articular cartilage is visible on the undersurface of the avulsed meniscus root without a true bony attachment. (B) Arthroscopic image of a left knee viewing the medial tibiofemoral compartment, demonstrating a type 5 MM posterior bony root avulsion fracture in a 16-year-old skeletally mature boy undergoing an isolated MM posterior root repair. A bony attachment is visible along the undersurface of the avulsed MM root (arrow), consistent with a bony root avulsion fracture. MFC, medial femoral condyle; MTP, medial tibial plateau. Figure 2A reproduced with permission from HSS Pediatric Orthopedic Surgery Service and Peter D. Fabricant, MD, MPH.
MMPRT Morphology and Frequency of Concomitant Meniscal Tears a
Data are presented as n (%). BHT, bucket-handle tear; MMPRT, medial meniscus posterior root tear.
The root tear classification is based on the system described by LaPrade et al. 26
Concomitant ligament injuries were frequent in this cohort, with 69% of patients undergoing a ligament reconstruction or repair(s) at the time of MMPRT repair. A single ligament procedure was performed in 57% of the cohort, most commonly involving the ACL (43%) or PCL (12%), while MLKIs (12%) were less common. Among the 13 surgically treated PCL injuries, complete femur-sided avulsions (85%) predominated while midsubstance tears (15%) were less frequent. An isolated MMPRT repair without ligament surgery was performed in 31% of patients (Table 3).
Surgically Treated Concomitant Ligament Injuries in Pediatric and Adolescent Patients Undergoing MMPRT Repair a
Data are presented as n (%). ACL, anterior cruciate ligament; MCL, medial collateral ligament; MMPRT, medial meniscus posterior root tear; MPFL, medial patellofemoral ligament; PCL, posterior cruciate ligament; PLC, posterolateral corner.
Ligament injuries were determined based on those that underwent concomitant surgical repair/reconstruction.
Skeletal Maturity Injury Pattern Subgroup Analysis
Compared with skeletally mature adolescents, skeletally immature patients more frequently underwent isolated MMPRT repair (60% vs 11%; P < .001) and sustained type 5 root avulsions (77% vs 40%; P = .002). Skeletally mature adolescents had higher rates of type 2 complete radial root tears (49% vs 17%; P = .004) and ≥1 concomitant ligament injury (89% vs 40%). Obesity was more common among skeletally mature patients (58% vs 27%; P = .008). Rates of delayed surgery (≥90 days after injury) did not significantly differ (27% for skeletally immature vs 40% for skeletally mature; P = .24). Medial compartment cartilage injury was also more frequent among skeletally mature adolescents (56% vs 30%; P = .029) (Table 4).
Characteristics of Skeletally Immature Versus Skeletally Mature Patients With MMPRTs a
Data are presented as mean ± SD (range) or n (%). All ligament injuries were determined based on those that underwent concomitant surgical repair/reconstruction at the time of MMPRT repair. Boldface type indicates statistical significance. BMI, body mass index; MMPRT, medial meniscus posterior root tear.
Age- and sex-adjusted percentile values. Obesity is defined as BMI ≥95th percentile.
Frequency, Location, and Severity of Concomitant Medial Tibiofemoral Compartment Cartilage Injuries
The resulting ICC was 0.98 (95% CI, 0.96-0.99) for the ICRS grading of medial compartment cartilage injuries, indicating excellent agreement between the 2 independent reviewers. There were no disagreements regarding the location (MFC and/or MTP) of the cartilage injuries between reviewers. Medial compartment cartilage injury was identified arthroscopically in 45% of patients (n = 34) at the time of surgery. Injury location was isolated to the MFC in 82% of cases, MTP in 12%, or involved both the MFC and MTP in 6%. Medial compartment cartilage injuries were most commonly ICRS grade 2 (62%) (Figure 3). High-grade lesions (ICRS grades 3 or 4) occurred in 24% of patients with medial compartment cartilage injury (Figure 4, Table 5).
Arthroscopic image of a right knee viewing the medial tibiofemoral compartment of a 16-year-old skeletally mature boy who underwent delayed (116 days after initial injury) anterior cruciate ligament reconstruction and a concomitant medial meniscus posterior root repair for a type 2 complete radial root tear. An International Cartilage Regeneration & Joint Preservation Society grade 2 cartilage injury is seen on the central to posterior weightbearing surface of the medial femoral condyle with partial-thickness fissuring. Reproduced with permission from HSS Pediatric Orthopedic Surgery Service and Peter D. Fabricant, MD, MPH.
Arthroscopic images of a left knee obtained in a 16-year-old skeletally mature boy undergoing delayed surgery (182 days after the initial injury) for an isolated medial meniscus (MM) posterior root tear. (A) Medial tibiofemoral compartment demonstrating a chronic-appearing MM posterior root tear, consistent with a type 5 root avulsion (arrow). (B) Concomitant International Cartilage Regeneration & Joint Preservation Society (ICRS) grade 3 cartilage injury of the medial femoral condyle (MFC; arrow) and associated ICRS grade 2 partial-thickness fissuring of the medial tibial plateau (MTP; arrow).
Frequency, Location, and Severity of Medial Compartment Cartilage Injuries Identified Arthroscopically at the Time of MMPRT Repair a
Data are presented as n (%). ICRS, International Cartilage Regeneration & Joint Preservation Society; MFC, medial femoral condyle; MMPRT, medial meniscus posterior root tear; MTP, medial tibial plateau.
Risk Factors for Medial Compartment Cartilage Injury Using Multivariable Logistic Regression
On bivariate analysis, patients with medial compartment cartilage injury were older (16.0 ± 1.6 vs 14.6 ± 2.6 years; P = .015), more frequently female (50% vs 24%; P = .021), and had higher BMI percentiles (86% ± 21% vs 76% ± 23%; P = .017), with a greater obesity prevalence (59% vs 34%; P = .033) compared to patients without medial compartment cartilage injury. Patients with medial compartment cartilage injury had longer times from initial injury to surgery (132 ± 121 vs 66 ± 76 days; P < .001), and delayed surgery (≥90 days after injury) was significantly more common (56% vs 17%; P < .001) in this group. Skeletal immaturity was less frequent among patients with medial compartment cartilage injury (26% vs 51%; P = .029). The prevalence of ≥1 concomitant ligament injury was also higher among patients with medial compartment cartilage injury than among those without medial compartment cartilage injury (82% vs 59%; P = .026). Because concomitant ligament injury may reflect injury severity, the rate of delayed surgery (≥90 days after injury) was additionally compared between patients with isolated MMPRTs and ligament-associated MMPRTs and was not significantly different (27% vs 37%; P = .61). Injury mechanism, including noncontact and sport-related injuries, was not significantly associated with medial compartment cartilage injury (Table 6).
Medial Compartment Cartilage Injury in Pediatric and Adolescent Patients Undergoing Medial Meniscus Posterior Root Tear Repair a
Data are presented as mean ± SD (range) or n (%). Boldface type indicates statistical significance. BMI, body mass index.
Age- and sex-adjusted percentile values. Obesity is defined as BMI ≥95th percentile.
On multivariable logistic regression using Firth penalization, delayed surgery (≥90 days after injury) was significantly associated with medial compartment cartilage injury (OR, 4.96; 95% CI, 1.64-15.01; P = .005) (Table 7). Increasing age was also significantly associated with medial compartment cartilage injury (OR per year, 1.33; 95% CI, 1.02-1.73; P = .032), corresponding to a 33% increase in odds per year. Obesity was not significantly associated with medial compartment cartilage injury (OR, 2.13; 95% CI, 0.75-6.07; P = .16). The model demonstrated excellent discrimination (C statistic, 0.80) and was statistically significant (likelihood ratio χ2 = 72.6; degrees of freedom = 3; P < .001).
Multivariable Logistic Regression (Firth Penalized) a
Model summary: Akaike information criterion = 80.6; likelihood-ratio χ2 = 72.6 (degrees of freedom = 3; P < .001); C statistic = 0.80. Boldface type indicates statistical significance.
Based on age- and sex-adjusted percentile values. Obesity is defined as BMI ≥95th percentile.
Sensitivity Analysis
In sensitivity analyses, delayed surgery (≥90 days after injury) remained associated with medial compartment cartilage injury in both models. In model 1, which included concomitant ligament injury, delayed surgery (≥90 days after injury) was associated with 5.47-fold higher odds of medial compartment cartilage injury (95% CI, 1.81-16.55; P = .003). In model 2, which additionally included age, delayed surgery (≥90 days after injury) remained associated with medial compartment cartilage injury (OR, 5.08; 95% CI, 1.65-15.67; P = .005). Concomitant ligament injury was not significantly associated with medial compartment cartilage injury in either model (Table 8).
Sensitivity Analyses of Risk Factors for Medial Compartment Cartilage Injury a
Model 1 included obesity, delayed surgery (≥90 days after injury), and concomitant ligament injury. Model 2 included age, obesity, delayed surgery (≥90 days after injury), and concomitant ligament injury. Boldface type indicates statistical significance. —, not applicable.
Model 1 summary: Akaike information criterion = 86.2; likelihood-ratio χ2 = 78.2 (degrees of freedom = 3; P < .001); C statistic = 0.77.
Model 2 summary: Akaike information criterion = 80.8; likelihood-ratio χ2 = 70.8 (degrees of freedom = 4; P < .001); C statistic = 0.80.
Discussion
The most important finding in this multicenter study was that delayed surgery (≥90 days after injury) was associated with concomitant medial compartment cartilage injury in pediatric and adolescent patients with MMPRTs. Increasing age was also associated with medial compartment cartilage injury. Importantly, the significant association between delayed surgery (≥90 days after injury) and medial compartment cartilage injury persisted in sensitivity analyses that additionally incorporated concomitant ligament injury as a surrogate for injury severity. Overall, medial compartment cartilage injury was arthroscopically identified in 45% of patients at the time of MMPRT repair. While the majority of these cartilage injuries involved the MFC and were classified as ICRS grade 2, nearly one-quarter were high-grade lesions (ICRS grade 3 or 4). These findings underscore the potential importance of timely recognition and surgical treatment of MMPRTs in this population.
Delayed surgery, commonly defined as operative treatment ≥90 days after injury, has been associated with higher rates of cartilage injuries in pediatric and adolescent patients with ACL tears.2,17,20,28,33 While this association may reflect persistent knee instability and secondary joint damage after the initial trauma,2,17,20,28,33 the underlying reasons for delayed surgical treatment are difficult to elucidate, likely multifactorial, and were not directly assessed in the present study. However, more than one-third of patients (35%) in the current cohort underwent surgery ≥90 days after injury. Importantly, the prevalence of delayed surgery did not differ between patients with isolated MMPRTs and those with ligament-associated MMPRTs. While further investigation is needed, the heterogeneous injury presentation of pediatric and adolescent MMPRTs and their limited representation in the literature may contribute to delayed recognition and subsequent delays in definitive surgical management.
Although many of the medial compartment cartilage injuries were low grade (ICRS grade 1 or 2), nearly one-quarter (24%) were high-grade lesions (ICRS grade 3 or 4). In the primary multivariable model, delayed surgery (≥90 days after injury) was associated with nearly 5-fold higher odds of medial compartment cartilage injury. This association remained consistent in sensitivity analyses incorporating concomitant ligament injury, suggesting that the observed relationship was not fully explained by injury severity in this cohort. While the current study was not adequately powered to assess risk factors specifically for high-grade cartilage lesions (n = 8), these patients underwent surgery at a mean of 189 ± 138 days after injury, and 75% had surgery ≥90 days after injury. While causality cannot be inferred from this retrospective study, the overall prevalence and severity of medial compartment cartilage injuries observed in this cohort support the need for heightened recognition and prompt evaluation of pediatric and adolescent patients with MMPRTs.
Increasing age was also associated with medial compartment cartilage injury, with each additional year in age increasing the odds by 33% (OR, 1.33). This observation aligns with prior studies on pediatric ACL and meniscal tears demonstrating that older adolescents, particularly those ≥14 years, are significantly more likely to present with cartilage injuries at the time of surgery.2,9,16,40 Collectively, these findings indicate that the risk of cartilage injury increases across adolescence, and that older adolescents with MMPRTs may be particularly at risk for medial compartment cartilage injury.
While adult MMPRTs are most commonly degenerative type 2 complete radial root tears,3,26,31,41 type 5 root avulsions were the most common MMPRT morphology (55%) in the current study. These findings are consistent with those from Wilson et al, 48 who reported that 89% (8/9) of their pediatric and adolescent MMPRTs were traumatic root avulsions. The predominance of type 5 root avulsions in younger patients is likely explained by the relative weakness of the cartilaginous physis and incompletely ossified epiphysis at the root attachment compared with the meniscal tissue itself.4,14 This biomechanical vulnerability may predispose the developing knee to a root avulsion rather than radial tearing through more mature meniscal tissue.
Notably, the majority of type 5 root avulsions in this cohort presented as complete soft tissue or chondral root avulsions without a discrete bony fragment (88%). This observation is consistent with findings from Clifton et al, 6 who reported that most of their pediatric MMPRTs (83%; 5/6) were complete soft tissue avulsions or contained a thin periosteal sleeve rather than a distinct bony fragment. These findings appear to contrast with the traditional LaPrade type 5 root tear classification, which describes a true bony root avulsion fracture in adults with mature subchondral bone. 26 As pediatric and adolescent medial meniscus posterior root avulsions may represent a distinct morphological pattern, a potential refinement to the existing LaPrade classification distinguishing soft tissue or chondral root avulsions (type 5A) from true bony root avulsion fractures (type 5B) may better characterize the predominant MMPRT morphology in this population. However, future studies incorporating standardized arthroscopic imaging and interobserver reliability assessment are needed to validate this proposed subtype.
Several skeletal maturity–related injury patterns associated with MMPRTs were identified in this study. Skeletally immature patients were significantly more likely to sustain isolated MMPRTs (60% vs 11%) while the majority of skeletally mature adolescents sustained ligament-associated MMPRTs (89%), particularly in the setting of an ACL, PCL, or MLKI. The MMPRT morphology also differed: type 5 root avulsions predominated in skeletally immature patients (77%), while skeletally mature adolescents demonstrated a more heterogeneous distribution, with type 2 complete radial root tears being the most common (49%), followed by type 5 root avulsions (40%). These maturity-related patterns may reflect increased sports participation and biomechanical changes associated with physeal closure, increased ligament stiffness, and maturation of subchondral bone.4,14 Cumulatively, MMPRTs in young patients do not appear to represent a uniform injury pattern, but possibly distinct maturity-related mechanisms of failure.
This retrospective multicenter study has some limitations. The retrospective and multicenter design limited the ability to assess and control for postinjury activity level, reinjury events, mechanical alignment, and other external factors that may have influenced the time to surgery or the development of medial compartment cartilage injury. As arthroscopic images were not available for all patients, arthroscopic descriptions from the operative reports were used to delineate MMPRT morphology and concomitant pathologies; however, only patients who underwent a transosseous root repair were included, and validated classification systems were used to improve the standardization of data. Standardized assessment of preoperative MRI for MMPRTs and/or partial concomitant ligament injuries was not feasible across participating institutions, precluding evaluation of diagnostic accuracy and its potential contribution to delays in surgical management. Additionally, cases were identified from meniscal repair procedures, potentially excluding MMPRTs treated with meniscectomy or left untreated. Although our study represents one of the largest cohorts of pediatric and adolescent MMPRTs, it may have been underpowered to detect smaller effect sizes. Finally, clinical outcomes were not assessed, and future studies are needed to determine the impact that medial compartment cartilage injury may have on patient-reported outcomes after MMPRT repair in this population.
Conclusion
Concomitant medial compartment cartilage injury was arthroscopically identified in 45% of pediatric and adolescent patients undergoing MMPRT repair. While most of these cartilage injuries involved the MFC and were classified as ICRS grade 2, nearly one-quarter were high-grade lesions (ICRS grade 3 or 4). Increasing age and delayed surgery (≥90 days after injury) were significantly associated with medial compartment cartilage injury. Overall, these findings underscore the potential importance of timely recognition and surgical treatment of MMPRTs in young patients.
Footnotes
Submitted January 1, 2026; accepted March 22, 2026.
One or more of the authors has declared the following potential conflict of interest or source of funding: L.V.T has received consulting fees from Ossur. A.E.J. has received support for education from Polaris Technology Solutions, Gotham Surgical Solutions & Devices, and Medwest Associates and hospitality payments from Abbott Laboratories. M.J.M. has received consulting fees from Smith & Nephew. J.C. has received consulting fees from Smith & Nephew and DePuy Synthes and support for education from Medwest Associates. P.D.F. has received consulting fees from WishBone Medical. R.F.L. has received consulting fees and royalties from Ossur, Smith & Nephew, and Elsevier, and research grants/support from AOSSM, AANA, Ossur, Arthrex, and Smith & Nephew.
