Femoral Peel-Off Lesions in Acute Posterolateral Corner Injuries: Incidence, Classification, and Clinical Characteristics

PurposeThe purpose of this study was to determine the incidence of acute avulsions of the popliteus tendon (PT) and lateral collateral ligament (LCL) of the femur (peel-off lesions) in knees with multiple injured ligaments. This study also describes the tear patterns and associations based on preoperative magnetic resonance imaging (MRI), physical examination, and arthroscopic inspection with injury patterns.MethodsThis was a retrospective review of a consecutive series of 48 acute grade III posterolateral knee repairs and reconstructions. All office evaluations were reviewed to determine the preoperative MRI examination results, the findings on physical examination with the patient under anesthesia, and the intraoperative arthroscopic findings.ResultsIn total, 19 patients (40%) were surgically verified as having peel-off lesions. Tears were typically categorized into 3 patterns: isolated PT tear (pattern 1) (4 of 19 [21%]), combined PT and LCL tears (pattern 2) (8 of 19 [42%]), and complex tears (associated intrasubstance- and/or fibula-based injuries) (pattern 3) (7 of 19 [37%]). Of the patients, 82% (14 of 17) showed conclusive MRI signs of femoral insertion separation and discontinuity. Examination with the patient under anesthesia showed tibial external rotation of greater than 10° in 84% of patients (16 of 19) and positive varus instability in 73% (11 of 15). Arthroscopic findings of acute avulsion and a positive lateral gutter drive-through sign were found in 94% (16 of 17).ConclusionsIn a series of 48 grade III, consecutive, acute posterolateral corner surgery cases, we found that 19 patients (40%) had peel-off lesions. For adequate clinical identification, we recommend a comprehensive diagnostic protocol, including MRI, physical examination, and arthroscopic inspection, to avoid underdiagnosis of the lesion in multiple ligament–injured knees. The lateral gutter arthroscopic evaluation is particularly sensitive for detecting the lesion.Level of EvidenceLevel IV, therapeutic case series.