The short answer
- Most runners can keep running if the knee isn't more swollen or stiff the next morning.
- Meniscus tears are common in knees that don't hurt at all. In people over 50, 61% of those with a tear on MRI had no knee symptoms in the previous month.
- For degenerative tears, surgery to trim the meniscus did no better than sham surgery, and exercise therapy did as well as surgery over two to ten years.
- In adults aged 18 to 40, early surgery wasn't better than exercise and education either. About a quarter of the exercise groups had surgery later, so starting with exercise keeps both options open.
- A knee that is locked and won't straighten, or that swells within hours of a twist, needs a medical assessment soon.
The knee has ached on the inside for a few weeks. You finally get a scan, and the report comes back with a sentence that sounds final: "Horizontal tear of the posterior horn of the medial meniscus."
It is easy to read that as damage that needs repairing before you can run again. For most runners, that isn't what it means.
What the scan is telling you
The menisci are two crescent-shaped pads of fibrocartilage between the thigh bone and the shin bone. They spread load across the joint. Like other tissues, they change with age and use, and some of those changes show up on MRI as tears.
That study didn't include people in their 30s and 40s, and it wasn't a study of runners. The point still carries: finding a tear doesn't prove the tear is causing the pain. An international guideline panel put it plainly, describing meniscus tears as common, usually incidental and unlikely to be the cause of knee pain, aching or stiffness2.
The history matters more than the picture. Researchers and guideline panels separate two broad situations.
- How it started
- Gradual or degenerativeCame on over weeks, or after an ordinary movement such as a squat or a run
- After a clear injuryA twist or impact you remember, often in sport
- Swelling
- Gradual or degenerativeLittle, or it comes and goes with load
- After a clear injuryThe knee swelled noticeably within hours
- Typical age
- Gradual or degenerativeMost often over 35
- After a clear injuryOften younger and active
- What the knee does
- Gradual or degenerativeAches, may catch or click
- After a clear injuryMay lock, give way or refuse to straighten
What the surgery trials found
The operation usually offered is arthroscopic partial meniscectomy, where the torn part of the meniscus is trimmed away. It is one of the few operations that has been tested against sham surgery.
Trials comparing surgery with exercise point the same way. In a Norwegian trial of 140 people with a mean age of 50, twelve weeks of supervised exercise did as well as surgery over two years, and thigh strength was better in the exercise group at three months5. Ten years later the two groups had similar knee function and similar rates of new osteoarthritis6. In a Dutch trial of 321 people aged 45 to 70 without a locked knee, 16 sessions of physical therapy over eight weeks were non-inferior to surgery for knee function over two years7.
Taken together, the evidence led an international panel of surgeons, physiotherapists, doctors and patients to make a strong recommendation against arthroscopic surgery for nearly all patients with degenerative knee disease, including those with a meniscal tear2.
Younger runners often assume their case is different. There is now a trial for them too.
What the exercise needs to be
The programmes in the trials weren't exotic. The Norwegian one used progressive strength and neuromuscular exercises two to three times a week for 12 weeks5. The Dutch one used 16 sessions over eight weeks of coordination work and strength exercises with the foot planted, such as squats and leg presses7.
You also don't need to spend those weeks in a clinic. The largest trial so far included 879 people aged 45 to 85 with knee pain, a degenerative meniscal tear and osteoarthritis. A three-month home exercise programme did as well for pain as the same programme with text-message reminders, and as well as adding in-clinic physical therapy10.
That trial was in an older group with osteoarthritis, not in runners. For runners the strength work usually has to go further, because running asks more of the knee than walking and stairs.
Can you keep running?
No trial has tested running itself in people with a meniscal tear, so here we're relying on reasoning and on what we know about running and knees.
That second part is reassuring. In a meta-analysis of 17 studies, hip or knee osteoarthritis was found in 3.5% of recreational runners, 10.2% of non-running controls and 13.3% of competitive runners11. Those studies can't prove cause and effect, but they give no support to the idea that recreational running wears the knee out.
If you've already stopped running, restart with short walk-run sessions on alternate days, and let the next-morning check decide how fast to build.
When surgery or a scan is worth discussing
A locked knee is the one mechanical symptom that the guideline panel left open as a possible reason for surgery2. A knee that swells quickly after a twist can mean a ligament injury or a tear that is worth repairing, and the evidence in this article wasn't built on those cases.