Meniscus
The two C-shaped cartilage cushions inside the knee — medial and lateral — what happens when they tear, and when surgery is necessary.
What they are
The meniscus is a crescent-shaped disc of tough, rubbery cartilage (technically fibrocartilage) that sits inside the knee between the femur (thighbone) and tibia (shinbone). Each knee has two menisci — the medial meniscus on the inside of the knee and the lateral meniscus on the outside. Together, they cushion the joint, distribute load, and help stabilize the knee.
The meniscus is thicker at the outer edge and tapers to a thin inner rim. Because of this C-shape, the inner edge can tear away or slip. The meniscus is made of tough collagen fibers arranged in concentric circles, which gives it the ability to absorb shock and resist tearing — up to a point.
How tears happen
Meniscus tears occur two main ways. Traumatic tears happen from a direct hit or an awkward twist, like pivoting on a planted foot. An athlete might feel a pop or catch in the knee. Degenerative tears happen slowly over time as the meniscus weakens with age or from repetitive minor trauma. A 50-year-old might tear their meniscus from a simple squat that wouldn’t have bothered them at 25.
Tears are described by location: the horn (the pointy front or back end of the C), the body (the main curved part), or the root (where the meniscus is attached to bone). The pattern and location matter for whether surgery is likely to help.
Symptoms
A torn meniscus typically causes pain on the inside or outside of the knee (depending on which meniscus is torn). Some patients feel a catch or locking sensation, as if the knee is getting stuck in certain positions. Swelling may develop. The pain is often worse with twisting, turning, or activities that load the knee on a bent leg.
Not all meniscus tears are painful. Some are discovered incidentally on an MRI done for another reason and cause no symptoms at all. Small, peripheral tears often cause no problems.
Diagnosis and imaging
An MRI is the gold standard for visualizing meniscus tears. It shows the location, pattern, and whether the tear is traumatic (clean) or degenerative (jagged edges). Physical exam findings like McMurray’s test or joint line tenderness support the diagnosis, but MRI is definitive.
The MRI finding alone doesn’t determine treatment. A small degenerative tear in a pain-free knee doesn’t need surgery. A larger traumatic tear with mechanical symptoms usually does.
When surgery is appropriate
- Traumatic tears in young, active patients. A clean tear from a specific injury, especially in an athlete, is an ideal candidate for repair. The surgeon sutures the meniscus back together, preserving the tissue.
- Tears with mechanical symptoms. Locking, catching, or instability suggest the torn piece is loose and moving. Surgery (either repair or removing the loose piece) restores smooth movement.
- Tears at the peripheral (outer) edge. The outer meniscus has a blood supply, so peripheral tears can heal if repaired. Inner tears have no blood supply and can only be managed by removing the torn segment (meniscectomy).
When non-operative care works
- Small degenerative tears in older patients. The knee may be asymptomatic or cause only mild discomfort. Rest, NSAIDs, and activity modification often suffice.
- Tears without mechanical symptoms. No locking or catching means the torn piece isn’t loose; it’s stable. The knee can function despite the tear.
- Partial meniscectomy is not a first option. Removing part of the meniscus is done when repair isn’t possible, but it accelerates cartilage wear over years. The goal is always to save meniscal tissue when possible.
Repair versus meniscectomy
Meniscus repair is the preferred operation when the tear is peripheral and the patient is young enough that blood supply will support healing. The surgeon sutures the tear closed and the meniscus heals in place. Recovery takes 4–6 weeks before return to sports.
Partial meniscectomy is removing only the torn, unstable portion. It’s used for degenerative tears at the inner rim (where there’s no blood supply) or when repair isn’t possible. Recovery is faster — days to weeks — but the long-term consequence is loss of meniscal tissue and slightly accelerated cartilage wear.