Recurrent patellar subluxation

1. What are factors that may predispose to patellar subluxation?
2. What are the signs and symptoms of patellar subluxation?
3. What imaging should be done to assess for subluxation?

Answers:
1. Less prominent lateral lip or more prominent medial lip, increased genu valgum/varus, excessive genu recurvatum, vastus medialis weakness, tibial external torsion, shallow lateral femoral condyle, laterally attached infrapatellar tendon.
2. Knee buckling, pain and tenderness in the peripatellar region, effusion, wasting of vastus medialis, impaired extension.
3. Lateral view in 45 degrees knee flexion and in full extension, sunrise view.