In a subtle effusion, fluid is detected by draining the medial subpatellar pouch proximally and applying pressure to the suprapatellar bursa: a rush of fluid back into the pouch is often seen.

It is this subtle effusion that is important to detect, should there be any questions as to whether pathology is intra- or extra-articular.

The retropatellar surfaces are checked for tenderness medially and laterally. These surfaces may be tender in the patellofemoral pain syndrome or chondromalacia patellae.

The knee is flexed at 45 degrees and checked for a pseudocyst. This presents as a tender fullness on the lateral joint line, which disappears with further extension or flexion.

The pseudocyst is caused by a ‘parrot beak’ tear of the lateral meniscus, buckling on itself and protruding from the lateral joint line (Cross & Watson, 1980).

A pseudocyst should be distinguished from a true meniscal cyst. A true cyst is usually larger than a pseudocyst, does not disappear with flexion and extension, and represents actual cystic changes in the meniscus.

The joint is palpated for a medial plica; this occurs in sixty percent of people and is usually asymptomatic. The medial plica runs from the medial joint wall to the anterior fat pad, and may cause medial pain and slight locking. At examination it may represent a tender cord medial to the patella and one finger’s breadth above its inferior pole.

The knee is flexed at 90 degrees; the patellar height is observed and checked for patella alta or patella baja. According to Insall, the patella lies high if its length is shorter than the length of the patellar tendon.

This patient demonstrates patella alta on the left. The right has been corrected surgically.