Sonographic evaluation of patellar clunk syndrome following total knee arthroplasty.

Patellar clunk syndrome is a painful mechanical phenomenon that may develop following total knee arthroplasty. The diagnosis is usually made clinically, but cross-sectional imaging may be needed to confirm the clinical suspicion. Sonographic confirmation of patellar clunk syndrome can be obtained by directly visualizing the soft tissue proliferation deep to the distal quadriceps tendon and by dynamically demonstrating the clunking tissue during flexion and extension of the knee.