Objectives: Trochlear dysplasia (TD) involves an abnormality of the shape & depth of the proximal aspect of the trochlear groove, and has been found in 85% of individuals with recurrent patellofemoral instability. (ref H. Dejour, 1994). TD has several characteristics including flattening/shortening of trochlear groove, the presence of a supratrochlear bump A trochleoplasty is a surgical procedure designed to help stabilize the patella by normalizing the shape of the trochlear groove. This study population is patients who underwent a patella stabilizing operation including a trochleoplasty, treated by a single surgeon between 12/06 &12/13. Methods: Surgical criteria for trochleoplasty: 1) recurrent lateral patella dislocations (LPD) who failed conservative management 2) Imaging: Dejour classification B or D 3) Physical Exam: "j-sign" 4) Symptoms: Instability not pain as primary complaint 5) No full thickness cartilage wear (CW) on articulating trochlear cartilage. Patients were prospectively followed with a patient outcome assessment tool, Knee injury and Osteoarthritis Outcome Score (KOOS). Pre- & post-operative imaging analysis was performed by the author. Results: 22 patients (28 knees) comprised the study population, representing 9% of surgeon’s population undergoing patella stabilizing surgery in same time period. Average age was 24 (range 14-47). 71% were female. 6 patients (12 knees) had bilateral (staged) procedures (6-22 mo). 21/28 (75%) patients had previous PF surgery. 8 patients had patella full thick CW; none had concomitant cartilage restoration. Concurrent surgeries: 11 Tibial tubercle osteotomies, 17 MPFL reconstructions, 7 medial imbrications. All needed lengthening of the lateral structures. 6 patients had second look arthroscopies, 3 at time of staged procedure & 3 for post-op stiffness. None had trochlear cartilage breakdown or softening. Radiographic findings: TD classification 13 ‘B’ /15 ‘D’, indicating all had a supra-trochlear spur. Patella height: I/S range (1.1-1.6), C/D range(1.1-1.7). TT-TG range (7-29mm), Tilt range (5-55°). All had improved sulcus angle at 20°: average deepening 9°, range 3-24°. All had elimination or reduction of supra-trochlear bump: pre-op range: 2- 12mm, post-op range 0-6mm. Follow-up: 1 year (82%), 2+ year 75% (15/20).Pre-operative KOOS scores showed substantial QOL impairment. Baseline KOOS (average): pain 74, symptoms 50, ADL 81, Sports 43, QOL 30. Postoperative KOOS scores showed clinically meaningful improvement in Sports (average 19) & Quality of Life (average 22). All patients reported improved conficence in their knee: no one reported further patella dislocating or subluxing events. Conclusion: Trochleoplasties remain a rare surgery for those patients with recurrent LPD. Most patients in this cohort had been previously operated on; many with patella cartilage wear at the time of surgery. Pre-operatively, many subjects report little disability in ADL’s but have poor QOL. Post-operative pain and symptom subscales remain stable. In the short term, trochleoplasty is a valid surgical option for patients with high grade trochleoplasty with a Supratrochlear bump, satisfactory trochlea cartilage surfaces, and a (+) J-sign. Improvement was found QOL and ADLs.