It’s definitely one of the more eye-opening orthopaedic diagnoses. It’s also a very real and irritating condition for those who experience it. So what is patellar clunk syndrome – and what can you do about it? Jon Smith explains.
What is patellar clunk syndrome?
Rarely has a medical condition been so vividly named. And as its title suggests, the condition affects the patella (kneecap) and feels like a clunk, almost like a car slipping into gear after a bit of struggle. In some cases the clunk is audible.
What causes patellar clunk syndrome (PCS)?
PCS affects people who have had a specific type of knee replacement featuring a posterior stabilized implant. When flexing or straightening the leg, a knot of fibrous scar tissue on the under-surface of the quadriceps tendon (just above where the tendon attaches to the patella) catches in the box of the implant. As the knot of tissue catches and then slips free, patients experience the notable clunk.
Does patellar clunk syndrome happen with all knee replacements?
No. It doesn’t happen at all with the modern implants used by Yorkshire Knee Clinic’s knee surgeons. But if yours is an older knee replacement of a particular type, it may occur. Although we have never used the posterior stabilized implant, we do see them very occasionally as patients ask for help in addressing the clunk.
Can you treat patellar clunk syndrome?
Yes, although it’s fair to say the best treatment of all is not to allow the clunk to develop in the first place by using a modern, well-aligned implant. PCS can be addressed by a revision (‘fix’) of the knee replacement. Whether that should happen would be a question of balancing the benefit against the risk – and this would always be decided on a case-by-case basis. Where the clunk causes only occasional or mild discomfort, it may be that surgery would be seen as an unjustifiable risk.
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