This study aims to compare the clinical outcome of Medial PatelloFemoral Ligament (MPFL) reconstruction with and without tibial tubercle transfer for recurrent patellar dislocation.

70 patients with recurrent patellar instability were randomly assigned to undergo MPFL reconstruction with or without tibial tubercle transfer. Follow-ups were performed at 12 and 24 months postoperatively, and computed tomography (CT) was performed immediately after the operation and at follow-up. The knee function was evaluated preoperatively and at 2 years postoperatively using Lysholm,Tegner and Kujala scales. Redislocation or multiple episodes of patellar instability were considered failures.

Inclusion Criteria:

• recurrent patellar dislocation or instability,patients with TT-TG value equal to or greater than 20 mm,patients with closed epiphyseal plate

TT-TG：Two lines drawn perpendicular to posterior bicondylar line, one line through middle of the trochlear groove(TG) and the second through tibial tuberosity (TT). Distance between the lines is measured.

Exclusion Criteria:

• bilateral patellar dislocation, a previous surgery in the involved leg,patients with open epiphyseal plate,patients with severe trochlear dysplasia