Patellar clunk syndrome is due to a suprapatellar fibrous nodule which develops at the junction between the proximal patella and the quadriceps tendon after total knee arthroplasty. Twelve patients (12 knees) who underwent arthroscopic treatment for the painful patellar crepitus or clunk after total knee arthroplasty had been followed at least for 1 year were enrolled. The average onset of symptom was 10.2 months (from 3 to 21 months) after total knee arthroplasty. All of the patients presented a painful crepitus, catching or clunk at the proximal patella, especially climbing stairs or rising from sitting. Both radiographic and clinical evaluations were done and for the clinical assessment, Knee Society Scores were recorded preoperatively and postoperatively. On their radiographic assessment, there was no evidence of component failure and in only one patient, joint line was elevated more than 8 mm. On arthroscopic examination, hypertrophic synovial tissue was identified at the junction of patella and quadriceps tendon in all patients. The hypertrophic synovial tissue did not engage completely in the intercondylar notch during flexion, but on extension, the lesion impinged on the distal part of anterior flange of femoral component at about 30 degrees to 40 degrees of knee flexion. On clinical assessment at the latest follow-up, the average knee score and function score increased from 63.8+/-4.6 to 90.9+/-3.2, 65.4+/-3.2 to 90.4+/-4.3 respectively. Arthroscopic debridement for soft tissue impingement at the patellofemoral joint following total knee arthroplasty showed satisfactory results.