Plica Syndrome of the Knee

What a plica is

During development in the womb, the knee is divided into compartments by thin membranes. These usually fade before birth, but in many people remnants remain as folds of the synovium (the lining that makes joint fluid). These folds are called plicae (singular: plica). Most people have at least one, and they normally cause no symptoms.

The four plicae are:

What causes plica syndrome

A plica becomes a problem when it is irritated, inflamed and thickened. The thick, less elastic band then catches on the edge of the thigh bone (the medial femoral condyle) as the knee bends and straightens, causing more irritation and sometimes wearing the cartilage underneath.

Triggers include:

• repetitive bending and straightening: running, cycling, rowing, swimming breaststroke, stair climbing, squatting
• a sudden increase in training load
• a direct blow to the inner knee
• twisting injuries
• weak quadriceps or tight hamstrings, which increase pressure on the front of the knee

Plica syndrome symptoms

• aching pain at the front of the knee, usually the inner side of the kneecap
• pain on stairs, squatting, kneeling and getting up from a chair
• pain after sitting with the knee bent for a long time (the "movie-goer's sign" shared with kneecap pain)
• clicking, snapping or popping as the knee bends, typically around 30 to 60 degrees
• a tender, sometimes palpable cord along the inner edge of the kneecap
• mild swelling at times
• a feeling of catching, although true locking is uncommon

Plica syndrome vs other causes of front knee pain

Plica syndrome often coexists with these conditions, especially patellofemoral pain.

Diagnosis

Plica syndrome is a clinical diagnosis made after other problems have been excluded. A doctor or physical therapist will:

• ask about activities, training changes and any injury
• feel along the inner edge of the kneecap for a tender, thickened band
• roll the band under the fingers while bending the knee to reproduce a click and pain
• test the menisci, ligaments and kneecap tracking

Imaging: X-rays are normal. MRI can sometimes show a thickened plica but is mainly used to rule out a meniscus tear or cartilage damage. Dynamic ultrasound can show the plica catching. The diagnosis is confirmed with certainty only at arthroscopy.

Treatment

First-line care (usually 6 to 12 weeks)

• Relative rest: reduce activities that cause pain, such as deep squats, kneeling, hill running and long periods sitting with bent knees. Keep active with pain-free exercise.
• Ice for 15 to 20 minutes after activity.
• Anti-inflammatory medicine such as ibuprofen or naproxen for short periods, following the label dose, if suitable for you.
• Physical therapy, the core of treatment.

Plica syndrome exercises

A physical therapist will tailor a program, which usually includes:

1. Quadriceps strengthening: straight leg raises, short-arc knee extensions, wall sits within a pain-free range, and progressing to step-downs.
2. Hamstring stretching: tight hamstrings increase pressure on the front of the knee.
3. Quadriceps and iliotibial band stretching and foam rolling.
4. Hip and core strengthening: side-lying leg raises, clamshells and bridges to improve knee alignment.
5. Gradual return to running or cycling, adjusting bike saddle height and training volume.

Injection

A corticosteroid injection into the plica or joint may calm inflammation when rehab alone is not working.

Arthroscopic surgery

If symptoms persist after about 3 months of good conservative treatment, an orthopedic surgeon may perform arthroscopic plica resection: removing the thickened fold through small incisions using a camera. It is a day procedure. Most people walk the same day, start rehab within a week and return to sport in about 6 to 8 weeks. Results are generally good when the plica is the true source of pain, especially in younger patients.

Outlook

Most people with plica syndrome recover with activity changes and rehabilitation. Surgery is needed only in a minority. Continuing quadriceps and hip strengthening and increasing training load gradually help prevent recurrence. If untreated over a long period, the rubbing plica can damage the cartilage of the femoral condyle.

Frequently asked questions

What does plica syndrome feel like?

It usually feels like an ache on the inner side of the kneecap, with clicking or snapping as the knee bends. Pain is often worse on stairs, when squatting and after sitting for a long time. Some people can feel a tender cord next to the kneecap.

How long does plica syndrome take to heal?

Most cases improve within 6 to 8 weeks of activity changes and physical therapy, though some take up to 3 months. If symptoms continue after 3 months of good rehab, arthroscopic surgery may be offered, followed by about 6 to 8 weeks of recovery.

Can plica syndrome go away on its own?

Often, if the aggravating activity is reduced. The plica itself remains, but the inflammation and thickening can settle. Strengthening exercises make recovery more reliable and reduce the chance of the problem returning.

Is it safe to run with plica syndrome?

Reduce or pause running while the knee is painful, especially downhill. Cycling with a higher saddle, swimming with a flutter kick, and strengthening exercises are usually tolerated. Return to running gradually once you can do daily activities and single-leg squats without pain.

Do you need surgery for plica syndrome?

Most people do not. Surgery is considered only when symptoms persist after about 3 months of physical therapy and other causes have been ruled out. Arthroscopic removal of the plica is a low-risk day procedure with good results in carefully selected people.