Meniscus tear: repair it, trim it, or leave it alone?

Two problems with one name

The meniscus is the rubbery, C-shaped cushion between the thigh bone and the shin bone. There is one on the inner side of each knee and one on the outer. A torn meniscus can mean two quite different things.

• A tear from an injury. A twist on a planted foot, often in football, cricket or kabaddi, mostly in people under forty. The tissue was healthy until it tore, and these tears often come with an ACL tear.
• A degenerate tear. The meniscus wears and frays with age, much as hair greys. It can tear with no injury at all, or getting up from a squat. By sixty, many knees have one, and most of their owners never know.

They are treated differently. Most of the confusion about meniscus surgery comes from treating the second kind like the first.

When to leave it alone

A degenerate tear in a knee that does not lock usually does best without an operation. This is one of the better-tested questions in orthopaedics. In a Finnish trial published in the New England Journal of Medicine in 2013, patients with a degenerate tear had either keyhole trimming or a sham operation, and neither they nor the people assessing them knew which. A year later the two groups were no different. In 2017 an international panel writing in the BMJ recommended against keyhole surgery for almost all degenerative knee problems.

So for a painful knee with a degenerate tear I start with physiotherapy for the thigh and hip muscles, pain relief, and time. Many settle over a few months.

If the knee is arthritic as well, the pain is more likely coming from the arthritis, and trimming the meniscus will not help it. That knee is treated as knee pain from arthritis, and deciding whether a knee needs replacing covers where that can lead.

When to repair it

I stitch a meniscus whenever the tear allows it. The meniscus spreads load across the joint, and a knee that loses a large piece of it is more likely to become arthritic in later years. Whether a tear can be stitched depends on three things.

• Where it is. The outer third of the meniscus has a blood supply and can heal. The inner part has almost none and will not heal, however well it is stitched.
• Its shape. A clean split running along the meniscus repairs well. A tear frayed into several flaps, or one through worn tissue, will not hold stitches.
• Your age and the knee. Younger tissue heals better. A repair done at the same time as an ACL reconstruction also heals better, probably because drilling for the graft releases blood and healing cells into the joint.

Two kinds of tear are urgent. In a bucket-handle tear a long strip flips into the middle of the joint, and the knee locks and will not straighten. It should be put back and stitched soon, within days to a few weeks, because the displaced strip stops being repairable. A root tear, where the meniscus comes away from its anchor at the back of the knee, leaves the joint almost as if the meniscus had been removed, and in the right patient it is repaired early for the same reason.

When to trim it

When a tear will not heal and is causing mechanical symptoms (catching, a painful click on twisting, or locking), the torn flap is trimmed back to a stable rim. Only the loose piece comes out. The rest of the meniscus stays.

Meniscus surgery is keyhole surgery either way, and almost always a day case. Often the final choice is made in theatre. An MRI shows most tears well but not all of them, and until I see the tear through the camera I can tell you only which is more likely. We agree beforehand what I will do in either case, so nothing comes as a surprise when you wake up.

Planning around the recovery

The two operations look the same from outside, with the same small scars. The months after them are very different.

• After a trim, crutches for a day or two if at all, back to desk work in a week or two, and most activity back within three to six weeks.
• After a repair, four to six weeks of protected weight on crutches, sometimes a brace limiting how far the knee bends, and four to six months before pivoting sport.

For a student in exam season, a farmer at harvest, or anyone whose work keeps them on their feet, that difference is a fair thing to raise before the operation. It is seldom a good reason to trim a tear that could be saved.

Further reading

• Sihvonen R, et al. Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. New England Journal of Medicine, 2013.
• Siemieniuk RAC, et al. Arthroscopic surgery for degenerative knee arthritis and meniscal tears: a clinical practice guideline. BMJ, 2017.
• American Academy of Orthopaedic Surgeons, OrthoInfo: Meniscus tears.

Common questions