Synovial tissue lines the knee joint and produces the fluid that lubricates it. A plica is a thickening of this synovial lining that separates the knee into compartments. These folds form in the fetus and shrink during the second trimester — and in most people, they shrink away or stay small. But in some, a fold stays thick and can irritate the knee. Could your knee pain be due to medial plica syndrome?
The knee has four plicae, but the medial plica causes most problems.
What is plica syndrome?
Plica syndrome is the term for irritation of a plica fold. Usually, it’s the medial plica — the fold on the inside of the knee — that becomes irritated and causes symptoms. The irritation mainly occurs when the knee bends, as the plica gets caught between the kneecap and the top of the knee joint.
Symptoms of plica syndrome
Irritation of the plica typically causes:
- Pain on the inside of the knee with repeated bending — climbing stairs, cycling, running
- Tenderness and swelling over the inner plica
- Snapping or clicking when bending the knee
- Sometimes, swelling and pain occur after a fall directly onto the knee
An X-ray is usually normal. A thickened, inflamed plica may be seen on MRI or ultrasound — though not always.
Occasionally, a suprapatellar plica blocks fluid flow within the joint, raising pressure at the top of the knee. That pressure can compress the quadriceps tendon, causing quadriceps tendonitis.
Plica or meniscal tear? How to tell them apart
It’s essential to exclude other causes of front or inner knee pain, such as a torn meniscus, patellofemoral arthritis, or patellar tendonitis. A meniscal tear tends to cause pain deeper in the joint and towards the back, worse with bending and rotating the knee. Kneecap arthritis causes pain behind the kneecap with joint swelling. Plica pain, by contrast, sits over the inner plica and is provoked by repeated bending.
Plica syndrome treatment
We try simple measures first. Ice, compression, and ibuprofen often settle the inflamed plica. Alongside that, a rehab programme reduces pressure on the plica — taping, stretching, and strengthening. One study found rehab effective in about 90% of cases.
If it doesn’t settle, an ultrasound-guided cortisone injection may help reduce the inflamed plica — placed accurately into the inflamed tissue inside the knee, or directed to the top of the knee for a suprapatellar plica.
Does keyhole surgery work for plica syndrome?
Keyhole surgery (arthroscopy) uses a small camera to find and remove the inflamed plica. The success rate is high when the plica is the genuine cause of pain, and there are no known complications from its removal. Where a suprapatellar plica is causing quadriceps tendonitis, removing it also helps the tendon.
But there’s an important caveat. Plica syndrome is hard to diagnose, and surgery carries risk — and its success depends on whether the plica is the only cause of the knee pain. Most studies on plica surgery are case series, which are lower-level evidence and do not prove effectiveness. So be cautious about surgery: it should only be considered after rehab and one or two cortisone injections have failed.
Frequently asked questions about plica syndrome.
How long does plica syndrome take to settle?
Many cases settle over a few weeks to a few months with rest, anti-inflammatories, and rehab — one study found rehab effective in about 90% of cases. Stubborn cases may need a cortisone injection, and only a minority need surgery.
Does plica syndrome always need surgery?
No — most cases improve without it. Surgery is reserved for cases that fail rehab and one or two cortisone injections, and only when the plica is confirmed as the cause of pain. Be wary of being told that surgery is the only and easy answer.
How is plica syndrome told apart from a meniscal tear?
Plica pain is localised over the inner plica and is brought on by repeated bending. In contrast, a meniscal tear causes deeper pain, often towards the back of the knee, worse with bending and rotation. Examination plus MRI or ultrasound clarifies which it is.
Can I exercise with plica syndrome?
Often yes, with modification — reducing the repeated deep-bending activities (stairs, cycling, running) that provoke it, while continuing rehab and non-aggravating exercise. A graded return follows as the irritation settles.
Can a plica be seen on a scan?
Sometimes. A thickened, inflamed plica may show on MRI or ultrasound, but not always, and a plica can be present without causing symptoms. That’s why diagnosis combines the clinical picture with imaging, rather than relying on a scan alone.
Final word from Sport Doctor London about medial plica syndrome
Plica syndrome is an uncommon cause of pain at the front of the knee, and most front-of-the-knee or inner-knee pain is not due to it. You need a good clinical assessment, together with imaging of an inflamed liver, to make the diagnosis confidently. Only consider surgery after rehab and one or two injections have failed, and be cautious of any practitioner suggesting surgery is easy and the only answer.
To book a knee assessment with Dr Masci in London, contact the team here or call +44 (0) 203 488 0350.
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