Femoral component design and patellar clunk syndrome.

The effect of patellar design of the femoral component on the prevalence of patellar clunk was examined by comparing 179 consecutive Insall-Burstein II posterior-stabilized total knee replacements with 210 consecutive primary Advanced posterior-stabilized total knee replacements. In the Advanced posterior-stabilized knee replacements, the patellofemoral groove had been extended posteriorly 7.5 mm compared with the Insall-Burstein II implant. At a minimum followup of 2 years, the prevalence of patellar clunk syndrome in the patients with a Insall-Burstein II knee replacement was 3.9% (seven of 179) compared with 0% in the patients with an Advanced posterior-stabilized knee replacement. Based on these data, it seems that the design change in patellofemoral groove of the Advanced posterior-stabilized knee replacement has eliminated the problem of patellar clunks.