The operation for a worn meniscus performed no better than a fake one.

PRP FOR A MENISCUS TEAR

That is not an opinion about arthroscopy. It is what happened when a degenerative meniscal tear was randomized against sham surgery, and it is the single most useful thing to know before agreeing to anything.

Two kinds of tear, and only one of them is a lesion

A traumatic tear happens to a healthy meniscus in a defined event — a twist, a tackle, a fall — usually in a younger knee. It can lock the joint, catch, or give way. That is a mechanical problem in otherwise sound tissue, and where it is repairable it should be repaired.

A degenerative tear is different in kind, not just in degree. The meniscus frays and splits as part of the same process that is thinning the cartilage around it. It is found on scans of enormous numbers of people who have no knee pain whatsoever. It is better understood as a marker of osteoarthritis than as a separate fixable injury.

Almost everyone who arrives here with “a meniscus tear” on a report has the second kind. The word makes it sound like the first.

What the sham trial actually showed

Patients with a degenerative meniscal tear and no arthritis were randomized either to arthroscopic partial meniscectomy or to a sham procedure — an anesthetic, incisions, the sounds and sensations of the operation, and no meniscal resection. At twelve months the groups were the same.

The implication is uncomfortable and worth sitting with: for this population, the benefit people reported after the operation was not coming from removing the torn tissue. Guidelines followed the evidence, and current knee osteoarthritis guidance does not support arthroscopic meniscectomy for degenerative tears in the absence of true mechanical locking.

Removing meniscal tissue is also not free. The meniscus distributes load across the joint surface. Taking some out raises contact pressure on cartilage that is already thinning, which is why meniscectomy is associated with later arthritis rather than protection from it.

So what is the tear actually telling you

In a degenerative knee the tear is a finding, not the diagnosis. The diagnosis is usually osteoarthritis, and the meniscal fraying is one of its features. That reframing changes the whole plan: you stop trying to fix a piece of tissue and start treating the joint it belongs to, which is set out on PRP for knee osteoarthritis.

It also changes what success looks like. Nobody is going to knit the meniscus back together with an injection, and we will not suggest otherwise. What is being aimed at is the environment of the whole joint — the synovium, the cartilage surface, the inflammatory tone inside the capsule.

What happens to these knees over twenty years

The decision about a meniscus is not really about the next six months. It is about the joint you will be standing on in twenty years, and there is long-horizon data on exactly that.

A cohort of 317 patients was re-examined 15 to 22 years after meniscal resection, alongside 68 unoperated people from population records. Symptomatic radiographic osteoarthritis was present in 27% of the operated knees against 10% of the controls — a relative risk of 2.6 (95% CI 1.3 to 6.1).

Then the part that belongs on this page rather than a surgical one. Within that operated group, the knees that did worst were distinguished by things that are not the meniscus:

• Obesity. Patients with a BMI of 30 or above had more radiographic osteoarthritis than those under 25.
• A degenerative tear rather than a longitudinal one — that is, the tear that was a symptom of the joint's condition rather than an injury to a healthy one.
• How much was taken. Total meniscectomy fared worse than partial resection.

The authors' own summary is the sentence this practice is built on, and it was published in 2004: systemic factors and local biomechanical factors interact. A degenerative tear in a metabolically unwell knee is not the same clinical object as a traumatic tear in a healthy one, even when the MRI report uses identical words for both. Which one you have changes the whole conversation — and what we measure to find out is on the metabolic health page.

Where the biology fits, honestly

The evidence here is thinner than for knee osteoarthritis generally, and the honest summary has three parts.

As an adjunct to surgical repair, in genuine repairable tears, PRP has the most support: systematic review of randomized trials in meniscal repair surgery suggests better healing rates when it is added. That is a question for the surgeon doing the repair, not an alternative to them.

For degenerative tears treated without surgery, the outcomes reported are variable — some people do well, some do not, and the imaging changes do not track the symptom changes reliably. That is a small and honest evidence base, and it is presented here as such rather than dressed up.

For the arthritic knee that happens to contain a degenerate tear, the case rests on the knee osteoarthritis evidence rather than on anything meniscus-specific. That is the strongest ground, and it is where most of these patients actually belong.

When it genuinely is mechanical

There is a group for whom none of the above applies, and missing them would be the real failure. A knee that truly locks — that physically will not straighten, because a displaced bucket-handle fragment is caught in the joint — is a mechanical block. That is the one presentation here where an operation is clearly indicated, and it is worth having the knee examined properly first so the surgical conversation is about a confirmed mechanical block rather than a reported tear. So does a large unstable flap causing genuine giving way, and so does a repairable tear in a young athletic knee.

“Locking” is worth defining carefully, because most people who report it mean something else: a knee that catches, twinges, or is stiff after sitting. That is not a block, and treating it as one leads to an operation that the sham trial says will not help.

What happens at the assessment

The examination establishes whether there is a true mechanical block, whether the joint line tenderness matches the reported tear, and how much arthritis is actually present — which is usually more than the patient has been told, because the report led with the tear. Imaging is read against the examination rather than instead of it.

And the metabolic picture gets looked at, for the same reason it does everywhere else on this site. A joint degrading in the presence of insulin resistance and metabolic inflammation is degrading for reasons an injection does not reach on its own.

What people ask when a scan finds a torn meniscus

Do I need surgery for a meniscus tear?

If the knee truly locks, or the tear is traumatic and repairable in a young knee, a surgical opinion is the right next step. For the far more common degenerative tear without locking, the randomized evidence says the operation does not outperform a sham, and guidelines have moved accordingly.

Can PRP heal a torn meniscus?

It will not knit the tear closed, and we will not claim it does. Where it is used, the target is the environment of the whole joint rather than the tear itself — which is a smaller and more defensible claim.

My knee catches. Is that locking?

Usually not. True locking means the knee physically cannot be straightened because something is caught inside it. Catching, twinging and stiffness after sitting are common in a degenerative knee and are not a mechanical block. The distinction decides whether a surgeon is the right answer.

If the tear is not the problem, why does my knee hurt where the tear is?

Joint line tenderness is common in arthritic knees whether or not a tear is present, because the structures at the joint line are all irritable in a degenerate joint. It is a genuinely confusing finding, which is why it is examined rather than assumed.

Related reading

• PRP for knee osteoarthritis
• PRP compared with surgery
• PRP compared with cortisone
• What we treat
• Metabolic health and tissue repair
• Am I a candidate?
• The knee injured in an event