BACKGROUND: Medial subluxation of the patella is a rare, disabling condition that has iatrogenic and traumatic causation. To date, only open reconstructions have been reported for operative treatment of this condition, but these procedures have a high rate of complications, revisions, and subsequent surgery. This is the first study to present the results of arthroscopic medial retinacular release for treatment of this problem. HYPOTHESIS: Arthroscopic release will alleviate painful medial patellar subluxation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Nine knees (7 patients) with painful, recurrent medial subluxation of the patella that occurred spontaneously (2 knees) or after a lateral release (5 knees) or an injury (2 knees) were treated with an arthroscopic medial retinacular release. The retinaculum was released 2 cm medial to the superior pole of the patella down to the anteromedial portal. At a mean follow-up of 2.7 years (range, 1-8 years), all knees were evaluated, and the results were graded according to the Merchant and Mercer rating scale. RESULTS: The mean age of the patients was 25 years (range, 15-38 years), and the mean duration of the subluxations before surgery was 28 months (range, 6-48 months). In all 7 patients (9 knees), the medial release relieved their medial subluxation and knee pain, and there were 6 excellent and 3 good results. There were no complications or further realignment surgery needed after this procedure. CONCLUSION: An arthroscopic medial retinacular release will successfully treat painful medial subluxation of the patella.