What Is Patellar Clunk Syndrome and What Can You Do About It?

Nicolas working with a patient at the clinic.

Below is a summary of the Patellar Clunk Syndrome presentation by our Physical Therapy Intern, Nicolas Ramos, created to give you an idea of what Patellar Clunk Syndrome (PCS) is and what you can do about it.

If you’ve had a total knee replacement and feel or hear a “clunk” or “pop” when straightening your leg, especially from a seated position, it could be Patellar Clunk Syndrome (PCS). This treatable complication, often linked to scar tissue behind the kneecap, can cause anything from harmless noise to significant discomfort or instability. With the right diagnosis and treatment plan, most people recover quickly and return to comfortable, confident movement.

Understanding Patellar Clunk Syndrome After Knee Replacement Surgery

If you’ve had a total knee replacement and feel or hear a “clunk” or “pop” when straightening your leg, especially from a seated position, it could be Patellar Clunk Syndrome (PCS). This treatable complication, often linked to scar tissue behind the kneecap, can cause anything from harmless noise to significant discomfort or instability. Understanding what PCS is, why it happens, and how to treat it is the first step toward recovery. With the right diagnosis and treatment plan, most people are able to return to comfortable, confident movement fairly quickly.

What is Patellar Clunk Syndrome?

Patellar Clunk Syndrome can develop after a posterior-stabilized total knee replacement (PS-TKR). It causes a distinct “clunk” or “pop” sound or sensation as the knee moves from bent to straight, usually between 30 and 45 degrees of extension. For some, it’s painless, while others experience discomfort or a feeling of instability. PCS most often appears within 3 to 12 months after surgery.

Why Does It Happen?

After surgery, a fibrous nodule of scar tissue may form behind your kneecap (patella). As you straighten your leg, this tissue can get caught in the groove between the thigh bone (femur) and kneecap, then suddenly release and cause a clunking sensation. Some common contributing factors include:

• Prosthetic design or component placement

• Small or low-positioned patella components

• Thick inserts used in the replacement

• Misalignment of the kneecap (called patellar mistracking)

• Pre-surgery inflammation or excessive scar tissue

Could It Be Something Else?

Yes, several other conditions can cause similar symptoms. It’s important to get an accurate diagnosis from your orthopedic surgeon and physical therapist. Possible alternatives to PCS include:

• Patellofemoral pain syndrome (PFPS)

• Tendonitis in the patellar or quadriceps tendon

• General knee instability

• Prosthetic failure

What Are The Treatment Options?

The good news is that PCS is treatable, and surgery isn’t always necessary, especially if it doesn’t significantly impact your quality of life or daily activities. Treatment generally falls into two categories: conservative (non-surgical) management, such as physical therapy, and surgical options listed below if needed. Here are the main approaches:

Conservative (Non-Surgical) Management:

• Physical Therapy:

• Strengthening your quadriceps

• Improving patellar tracking

• Enhancing overall knee stability

• Activity Modification: Avoiding deep squats and positions that provoke the clunk

• Pain Relief: Use of NSAIDs (like Ibuprofen) or Corticosteroid injections

Surgical Options (If Needed):

• Arthroscopic removal of scar tissue

• Resurfacing the patella

• Adjusting the prosthetic components

Prognosis and Moving Forward

With proper management and treatment, many patients experience better function and fewer symptoms. Before moving forward, ask yourself the questions below:

• Can you do your daily tasks with confidence?

• Can you train through the noise/sensation to rebuild strength?

• Can you get in/out of a chair, car, or toilet without fear or discomfort?

• Are you overall satisfied with your knee replacement?

If you answered “no” to any of these, speak with your orthopedic surgeon and physical therapist about creating a personalized plan to help you reach your goals. In some cases, surgery may be needed to remove excess tissue. Regardless, progressively strengthening the muscles around your knee is key to achieving the quality-of-life improvements expected after a total knee replacement.

Final Thoughts

PCS can be a frustrating post-op experience, but it’s not permanent. Physical therapy is essential for reducing symptoms and restoring knee function. If you’re hearing or feeling a “clunk” and aren’t sure what to do next, we can work together to get you moving confidently again. If you have questions about your symptoms, contact our clinic to schedule a session because your knees are worth it!