This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Patellar cluck syndrome is interposition of soft tissue at or hyperophied scar: 
Select and explain. 
A. Superior pole of patella and impinging on femoral component during flexion, B. Superior pole of patella and impinging on femoral component during extension, C. Inferior pole of patella and impinging on femoral component during flexion, D. Inferior pole of patella and impinging on femoral component during extension
B: Superior pole of patella and impinging on femoral component during extension
Answer: B: Superior pole of patella and impinging on femoral component during extension 
Explanation: Ans: B. Superior pole of patella and impinging on femoral component during extension Patellar Clunk Syndrome is a painful condition associated with a mechanical catching or clunking during active extension following total knee ahroplasty (TKA).The syndrome is caused by growth of interposing soft tissue usually at the superior pole of the patella.This interposed soft tissue cannot be visualized on plain radiographs.