Meniscal tears are a common cause of knee pain and swelling. The meniscus is a c-shaped cartilage that sits between the knee bones and cushions the joint. In some people, the meniscus — especially the lateral meniscus — is abnormally shaped, which makes it more prone to injury. So what is a discoid lateral meniscus, and what should you do if you have one?
What is a discoid meniscus?
A healthy meniscus is crescent-shaped, like a C. In some people, the meniscus is shaped like a disc instead. This abnormal shape makes it much larger and more likely to tear, and the blood supply to its outer edge is reduced — which limits healing.
A discoid meniscus is relatively common, occurring in up to 15% of people. Most cases affect the outer cartilage — a lateral discoid meniscus.
Is a discoid meniscus hereditary?
We think so. One study found a discoid meniscus in a father and his children, which points to an inherited tendency.
Symptoms of a discoid meniscus
Most people never know they have one, and live without any problems. It’s often found by chance on an MRI scan or during knee arthroscopy — and in most cases, we leave it well alone.
In some people, though, the abnormal shape causes the meniscus to catch or tear. Common symptoms of a problematic discoid meniscus include:
- Pain on the inside or, more often, the outside of the knee
- Knee joint swelling
- A popping sensation with activity
- Catching or locking of the knee
- Pain with squatting or kneeling
A classic feature in children is a painless “clunk” as the knee moves — sometimes called snapping knee syndrome.
Diagnosis
We diagnose a discoid meniscus from the history of pain and mechanical symptoms, combined with imaging. MRI usually confirms it and rules out other causes.
Discoid meniscus on MRI
A discoid meniscus loses the normal C-shaped contour. It’s thicker than usual, so more meniscus appears across more image slices — the feature radiologists rely on. MRI also shows any meniscal tear or meniscal cyst.
Discoid mniscus treatment
If the meniscus isn’t causing problems, we leave it alone — no treatment is needed.
For a painful discoid meniscus, we start with simple measures: NSAIDs such as ibuprofen, and physiotherapy focused on quadriceps and lower-limb strengthening.
Sometimes we use cortisone to reduce swelling around a tear. We use ultrasound to guide the needle close to the torn meniscus and inject a small dose of cortisone around it, which reduces the inflammation associated with the tear. Ultrasound improves the accuracy of the injection and minimises side effects.
We suggest surgery only for people with more severe pain or mechanical symptoms.
Surgery
Knee arthroscopy (keyhole surgery) uses a camera to guide miniature instruments. For a discoid meniscus, the procedure depends on the problem.
If a discoid lateral meniscus tears, we can repair it, remove part of it, or — commonly — repair one part and remove another. Surgeons often reshape the abnormal meniscus into a C-shape, a procedure called saucerisation.
The important principle is to preserve as much meniscus as possible. Results after partial removal or repair are good, but removing the whole meniscus leads to earlier arthritic change. So current evidence favours saucerisation with repair, rather than complete removal.
Frequently asked questions
Is a discoid meniscus a problem?
Usually not. Most discoid menisci cause no symptoms at all and are found by chance. It only becomes a problem if it tears or catches, causing pain, swelling, locking, or a clunk. A discoid meniscus seen on a scan doesn’t need treatment unless it’s causing symptoms.
Which knee is affected — inside or outside?
Almost always the outside. Over 90% of discoid menisci involve the lateral (outer) meniscus, so symptoms are usually felt on the outer side of the knee. A discoid medial meniscus is very rare.
Do you always need surgery for a discoid meniscus?
No. A painless discoid meniscus is left alone, and a painful one is first managed with anti-inflammatories, physiotherapy, and sometimes a guided injection. Surgery is reserved for significant pain or mechanical symptoms such as locking — and when it’s done, the aim is to preserve the meniscus, not remove it.
What is saucerisation?
It’s the keyhole procedure that reshapes an abnormal meniscus back into a more normal C-shape, trimming the excess central tissue while keeping the outer rim. It’s usually combined with repair of any tear, and preserving the meniscus this way protects the knee from earlier arthritis.
Can you play sport with a discoid meniscus?
Yes — most people with this issue play sport without ever knowing they have one. If it becomes symptomatic, strengthening and load management usually allow a return to activity, with surgery considered only for persistent mechanical problems.
Final word from Sport Doctor London about a discoid lateral meniscus
A discoid meniscus is a relatively common, often silent, variation in the shape of the knee cartilage — and a cause of pain on the outer part of the knee when it becomes symptomatic. Most cases need no treatment and are simply found on MRI. Where it does cause problems, see an experienced sports doctor to find the best option, and preserve the meniscus wherever possible.
If you have outer knee pain, clicking, or locking, Dr Masci can assess you in London, including ultrasound in clinic. Contact the team here or call +44 (0) 203 488 0350.
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Thank you
This was insightful and it helped me understand my diagnosis better. Appreciate it!
Thanks for the positive comment and I’m glad I’ve clarified it a bit better for you.