The anteromedial retinaculum in ACL-injured knees: An overlooked injury?

PURPOSE: The purpose of this study was to retrospectively analyse the pattern of injury to the medial knee structures in anterior cruciate ligament (ACL) injured patients. It was hypothesised that anteromedial injuries would be more common than posteromedial lesions.

METHODS: One hundred and twenty subjects aged 18-25 years with a primary ACL injury were included. Patients were excluded if the time between injury and magnetic resonance imaging (MRI) was more than 28 days or if a knee dislocation or fracture was present. The MRIs were analysed with particular emphasis on injuries to the medial knee structures, menisci and bone bruise patterns. Injuries to the ligaments and anteromedial retinaculum (AMR) were graded according to severity, ranging from periligamentous oedema (grade I), partial fibre disruption of less or more than 50% (grade IIa or IIb) to complete tears (grade III).

RESULTS: AMR injury was seen in 87 subjects (72.5%) on the coronal plane and in 88 (73.3%) on the axial plane, with grade III lesions observed in 27 (22.5%) and 29 knees (24.2%). Injuries to the superficial medial collateral ligament (sMCL), deep MCL (dMCL) and posterior oblique ligament (POL) were detected in 60 patients (50%), 93 patients (77.5%) and 38 patients (31.6%). However, grade III injuries to the POL were observed in only seven knees (5.8%). Medial meniscus injuries were associated with lesions of the sMCL and AMR (p < 0.05), while lateral meniscus injuries were significantly more common in patients with dMCL rupture (p < 0.05).

CONCLUSION: Data from this study suggest that injuries to the AMR are much more common than posteromedial lesions in subjects with ACL injuries.

LEVEL OF EVIDENCE: Level IV.