Arthroscopic Treatment of Mucoid Hypertrophy of the Anterior Cruciate Ligament

Purpose: The purpose of this study was to examine the clinical features and diagnosis of patients with mucoid hypertrophy of the anterior cruciate ligament (ACL) and to assess the results of arthroscopic treatment. Methods: Between May 1999 and August 2005, 156 knees in 132 patients were diagnosed with mucoid hypertrophy of the ACL and underwent arthroscopic treatment. Of these, 106 knees in 91 patients (86 women and 5 men), with a mean age of 61 years (range, 42 to 80 years), were followed up for at least 2 years. All 106 knees had central knee pain on terminal extension without preceding trauma, and 83 (78.3%) had extension deficit. Magnetic resonance imaging showed thickened, ill-defined ACLs with increased intraligamentous signals. Arthroscopy showed osteoarthritic changes of varying degrees in all, with 84 (79.2%) having intercondylar notch narrowing and 102 (96.2%) having additional degenerative pathologies. The posterolateral portion of the ACL appeared hypertrophied, which impinged on the lateral wall and roof of the notch. Arthroscopic debridement of hypertrophied ACLs was performed with or without notchplasty, according to the severity of impingement. Results: Good to excellent pain relief on terminal extension was obtained in 92 of 106 knees (86.8%), including complete pain relief in 57 (53.8%). The extension deficit was normalized in 68 of 83 affected knees (81.9%). Lachman and anterior drawer tests showed a firm endpoint in all, and 85.8% showed good to excellent subjective satisfaction. Conclusions: Mucoid hypertrophy of the ACL should be suspected in elderly women presenting pain on terminal extension without preceding trauma, especially when associated with extension deficit. The magnetic resonance imaging findings are specific for preoperative diagnoses. Partial ACL debridement with notchplasty provides safe and effective symptom relief. Extension pain improved significantly in 92 of 106 knees (86.8%), and extension deficit was normalized in 68 of 83 knees (81.9%). Level of Evidence: Level IV, therapeutic case series.