The Association Between Medial Meniscus Extrusion and Lesion Location of Juvenile Osteochondritis Dissecans of the Medial Femoral Condyle.

BACKGROUND

Osteochondritis dissecans (OCD) of the medial femoral condyle (MFC) is a common disorder in juvenile knees, although its biomechanical etiology remains unclear. Medial meniscus extrusion (MME) has been implicated in joint overload and degenerative changes; however, its relationship with lesion-specific OCD pathogenesis, particularly in inferior-central MFC lesions, has not been elucidated.

METHODS

This cross-sectional study included 56 knees from 47 patients (18 y or younger) who underwent surgical treatment for OCD. Lesions were categorized into MFC-classical/extended classic (MFC-C/EC, n=22), MFC-inferior-central (MFC-IC, n=12), and lateral femoral condyle (LFC, n=22). MME was quantified using the relative percentage of extrusion (RPE) on coronal magnetic resonance imaging (MRI). Radiographic parameters included lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA). Nonparametric statistical analyses were performed, and a post hoc power analysis confirmed adequate sensitivity (power=84.3%).

RESULTS

RPE was significantly greater in MFC-IC (33.6%) compared with both MFC-C/EC (17.6%) and LFC lesions (18.1%). LDFA was significantly lower in LFC than in MFC-C/EC (80.4˚ vs. 82.4˚). A moderate negative correlation was found between RPE and MPTA ( r =-0.41), while LDFA showed no significant association with RPE. Linear regression identified MPTA as a significant predictor of RPE (slope=-1.30%/degree).

CONCLUSION

MME is significantly associated with inferior-central OCD lesions in juvenile knees, suggesting that altered mechanical loading may contribute to their development. Evaluation of meniscal extrusion and tibial alignment may aid in identifying at-risk patients and developing lesion-specific preventive strategies.

LEVEL OF EVIDENCE: Level III-cross-sectional comparative study.