The clunk syndrome is a rare complication of the posterostabilized total knee arthroplasties.

In the literature, there is a lot of aetiologies described concluding to a multifactorial disease.

The aim of our study is to analyse the risk factors described in the literature in a serie of clunk syndrome occurring in three different prosthesis.

We retrospectively analyzed all our cases of clunk syndrome. We compared radiographic values before and after the intervention: the Insall-Salvati ratio, the joint line modification, the thickness of the patella and position of the tibial tray. We compared the appearance of the clunk in three different types of new generation prosthesis: Scopio NRG (Stryker), Legacy (Zimmer) and Sigma (DePuy). The bone scan was done preoperatively to confirm diagnosis.

There are four cases of clunk in each group of prosthesis which represents an mean incidence of 0,5 %. All the clunks occurred in female patients. There is three bilateral cases and one homolateral recurrence. We find no difference in the preoperative values compared to the postoperative status. There is no difference between the three groups. The bone scan was done in eight cases and returned positive in seven cases.

All our cases of clunk syndrome occurred in female patients which is our first risk factor. Doing a clunk syndrome on one side is a great risk factor of doing a clunk on the other side if implanted. The diagnosis of the syndrome is mostly clinical but the bone scan is frequently positive.

The patellar clunk syndrome remains a rare complication of posterostabilized TKA.

Being a woman and one episode of clunk are two risk factors. In presence of symptoms, the bone scan is a reliable preoperative exam to confirm the diagnosis.