Patellar clunk

What actually makes the noise in patellar clunk?

A clunk may be associated particularly with a posterior stabilised knee replacement.

The sound (and symptom) may first appear about 7 months after the surgery and the noise usually happens when the knee extends. It is caused by a nodule of scar tissue which may develop at the back of the lower part of the quadriceps tendon, and which gets trapped as the patella engages the 'box' of the implant (which encloses the stabilising 'cam and post') - and then releases with a painful clunk.

Patients with pre-existing patella baja are at particular risk of developing patellar clunk syndrome after knee replacement.

Back to top

Minimising the risk of initiating a clunk during initial surgery

The most important factor in this syndrome is the patellar tendon length, particularly if there is pre-existing patella baja.

The surgeon is likely to try to remove less of the femur during surgery to tension the extension gap and minimise the risk of patellar tendon shortening. Also the patellar height seems to be important, and the surgeon will try to maintain adequate patellar height. Both of these measures may reduce the contact between the quadriceps tendon and the top of the intercondylar notch.

Back to top

How is patellar clunk syndrome managed?

Surgery is generally required to fix the problem, although the patient may be sent to physiotherapy before surgery to strengthen the quadriceps and hamstrings muscles.

Surgery is usually arthroscopic, during which the nodule of scar tissue is debrided and removed, resolving the problem.

Back to top

Other relevant links on KNEEguru

A-Z Keywords

Total knee replacement, Total knee replacement failure and revision, Prosthesis choice

Forum discussions

• Re: Eureka???!! - Patients discussing clunks in the knee.

Back to top