*3.2.7 Tests for associated meniscal injury*

The medial and lateral joint lines should be examined for areas of tenderness. Medial joint line tenderness is suggestive of meniscal tear, arthrosis, or tear of the patellomeniscal ligament along its course to insertion on the anterior horn of the medial meniscus [30]. McMurray's test and Thessaly test are performed to rule out meniscal tear. The Thessaly test [57] is performed as follows: The patient stands on one leg while holding the examiner's hand for support. The examiner instructs the patient to rotate the body and leg internally and externally 3 times with the knee bent at 5 degrees and then at 20 degrees. The test should be first performed on the unaffected side so that the patient can properly perform movement as a practice run before testing the affected knee. The test is considered positive when pain or clicking occurs at the joint line. A locking or catching sensation is also suggestive of meniscal injury.

### *3.2.8 Tests for associated cruciate and collateral ligament injury*

Patellar symptoms may be masked due to presence of concomitant anterior cruciate ligament deficiency; therefore, the Lachman and pivot shift tests should be performed. Posterior cruciate ligament insufficiency has been reported to be associated with patellofemoral arthrosis. Hence, the posterior drawer test is also an essential part of a complete physical examination. Valgus testing to determine the integrity of the medial collateral ligament is important in patients with a patellar dislocation because simultaneous medial collateral ligament and MPFL injuries can occur.

After completion of the physical examination, aspiration of an intra-articular effusion can be done to determine the diagnosis. A hemarthrosis implies a traumatic injury, whereas serosanguinous fluid may indicate an articular cartilage lesion. In patients with acute dislocations of the patella, it is important to examine the aspirate for the presence of fat droplets, which indicate the presence of an associated osteochondral fracture [50].
