Medial patellar subluxation (MPS) is normally described following a lateral release. We report on a 14-year-old girl with MPS without previous lateral release. Arthroscopic examination demonstrated MPS at 0 and 30° of flexion, and the patella was tight in flexion on the lateral side. A low lateral release with a tibial tubercle transfer was performed, followed by repair of the lateral release with an iliotibial band flap, and lateral patellofemoral ligament reconstruction. Excellent functional outcome was achieved. This type of patellar instability is often overlooked and a high index of suspicion is needed for appropriate diagnosis and treatment.