Medial subluxation of the patella as a complication of lateral retinacular release.

We examined 54 patients (60 knees) referred to us because of their failure to improve, or because of a worsening of their preoperative symptoms, following an arthroscopic lateral retinacular release. Thirty knees developed medial subluxation of the patella postoperatively. This disabling condition is new to us. It is previously unreported as a complication of arthroscopic lateral retinacular release. Anterior knee pain was the only reported preoperative symptom in 14 knees. Sixteen knees had a preoperative diagnosis of lateral patellar subluxation on the basis of a positive apprehension sign only. Eighteen of 30 knees had no surgery of the extensor mechanism other than the arthroscopic lateral release. The remainder additionally underwent varying types and numbers of operations in an attempt to resolve their disability. CAT scan evaluation of three patients who volunteered for the procedure demonstrated severe atrophy and retraction of the vastus lateralis. Loss of this dynamic lateral stabilizer contributed to the medial subluxation of the patella.