Arthroscopic treatment of soft-tissue impingement under the patella after total knee arthroplasty

There has been an increased number of reports of complicated diseases of the patellofemoral joints after total knee arthroplasty (TKA). We treated soft-tissue impingement under the patella after TKA by arthroscopic surgery and investigated the findings and efficacy of the treatment. Six patients and 8 knees that showed soft-tissue impingement of patellofemoral joints after TKA were treated by arthroscopic surgery. We classified the patients with soft-tissue impingement under the patella into 3 groups: (I) patellar clunk syndrome, the isolated fibrous nodule located in the suprapatellar lesion without the other fibrous tissues causing the impingement (n = 2); (II) impinging hypertrophic synovitis, generalized hypertrophic synovitis with no fibrous nodule (n = 4); and (III) the combination of types I and II, the suprapatellar fibrous nodule with generalized hypertrophic synovitis (n = 2). Therapeutic efficacy was in type I, 2 were good to excellent; in type II, 3 were fair and 1 was poor; and in type III, 2 were fair. Better results were obtained in type I (a patellar clunk syndrome) than in type II (impingement synovitis).