Knee joint

Cause, clinical and ultrasound findings

• Reasons for the injection include rheumatoid arthritis, osteoarthritis, gout, calcium pyrophosphate deposition and trauma.

• A painful knee joint may present with capsular-pattern (Cyriax) limited flexion with a hard end feel. The knee will have a varying degree of effusion.

• Fluid is present in the suprapatellar pouch and in the medial and lateral recesses, which on ultrasound appear anechoic.