Patellar crepitation in the P.F.C. sigma total knee system.

Painless and painful patellar crepitation and patellar clunk syndrome represent a spectrum of peripatellar scar formation particular to posterior-stabilized knee components, although it may occur with cruciate-retaining designs as well. The formation of peripatellar inflammatory scar tissue is related to implant design and surgical technique, with microscopic and gross findings indicating varying degrees of inflammatory fibrous hyperplasia. These well recognized clinical entities have an incidence ranging between 1% and 5% in different series. The majority of patients with mildly painful or painless patellar crepitation will improve within 6 months to 1 year. In patients with more disabling symptoms such as catching, early intervention with open scar excision should be considered.