What the meniscus does.
Each knee has two menisci, C-shaped wedges of fibrocartilage sitting between the thigh bone and the shin bone, one on the inner side and one on the outer. They spread load across the joint surface, add stability and help distribute the fluid that lubricates the joint. Remove one entirely and the contact stress on the cartilage beneath rises substantially, which is why total meniscectomy is no longer performed.
Two very different things with the same name.
This is the single most useful distinction in the whole topic.
- A traumatic tear happens to a healthy meniscus, usually in a younger person, from a twisting injury on a loaded knee. There is a moment of injury the patient can name. The knee often swells over hours and may catch, lock or give way.
- A degenerate tear happens to a meniscus that has been softening for years. There is frequently no injury at all, or a trivial one. It is part of the same process as osteoarthritis rather than a separate event, and it becomes steadily more common with age.
Degenerate meniscal tears are extremely common in people with no symptoms. Imaging studies of asymptomatic middle-aged and older adults find meniscal tears in a large proportion, and the rate rises with age. So finding one on your MRI does not establish that it is causing your pain.
What the evidence says about surgery.
This is one of the better-studied questions in orthopaedics, and the answer is consistent.
For degenerate tears, multiple randomised controlled trials have compared arthroscopic partial meniscectomy against physiotherapy, and in some cases against placebo surgery in which an arthroscopy was performed but nothing was resected. They have not shown a meaningful benefit for the surgery. Systematic reviews reach the same conclusion. Guideline bodies now recommend against arthroscopic surgery for degenerative knee disease.
For traumatic tears, particularly in younger patients, surgery retains a clear role. Where the tear is in the outer, better vascularised portion, repair rather than resection is preferred, because preserving the meniscus preserves the joint.
There is one situation that does justify prompt surgery regardless of age: a genuinely locked knee, where a displaced fragment physically blocks the joint from straightening. That is a mechanical problem with a mechanical solution.
Diagnosis.
The history does most of the work: whether there was a real injury, the age of the patient, and whether there is genuine mechanical locking as opposed to pain-related hesitancy. Examination looks for joint line tenderness, effusion and a block to full extension. A weight-bearing radiograph is important because it establishes whether arthritis is present, which changes the interpretation of any MRI entirely.
Treatment.
For a degenerate tear, treatment is that of the underlying arthritis: exercise, weight management, load modification and analgesia. Where arthritis is advanced and symptoms justify it, knee replacement is the operation that helps, not arthroscopy.
For a traumatic tear in a younger knee, referral for arthroscopic repair is appropriate, and that is performed by a knee arthroscopy surgeon.
Where this practice fits.
Professor Rodda's practice is focused on hip and knee replacement. He does not perform joint-preserving surgery such as arthroscopy or osteotomy. If your condition is at a stage where preservation surgery is the right option, you will be told that and referred to a colleague who does it, within Sunshine Coast Orthopaedic Group or elsewhere. Where the joint has reached the point that replacement is the reasonable option, that is the work done here.
Common questions.
My MRI shows a meniscal tear. Do I need surgery?
Usually not, if you are middle-aged or older and the tear is degenerate. Randomised trials, including trials against placebo surgery, have not shown a meaningful benefit from arthroscopic surgery for degenerate meniscal tears. Surgery retains a role for traumatic tears in younger knees and for a genuinely locked knee.
What is the difference between a traumatic and a degenerate tear?
A traumatic tear happens to a healthy meniscus through a specific twisting injury you can usually name. A degenerate tear happens gradually in a meniscus that has been deteriorating with age, often with no injury at all, and it is part of the arthritic process rather than separate from it.
Can a meniscal tear heal?
Only the outer third has a good blood supply, and tears there can heal, especially if repaired. Tears in the inner portion have little blood supply and do not reliably heal. Symptoms can settle even when the tear does not.
What does a locked knee mean?
A knee that physically will not straighten because a displaced fragment of meniscus is caught in the joint. It is different from a knee that is stiff or sore to straighten. True locking is one of the clear indications for prompt arthroscopic surgery.
Will removing the meniscus cause arthritis?
Removing meniscal tissue increases contact stress on the cartilage, and larger resections are associated with a higher rate of later osteoarthritis. This is why repair is preferred where possible and why total meniscectomy is no longer done.
References.
- Thorlund JB, Juhl CB, Roos EM, Lohmander LS. Arthroscopic surgery for degenerative knee: systematic review and meta-analysis of benefits and harms. BMJ. 2015;350:h2747.
- Sihvonen R, Paavola M, Malmivaara A, et al. Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. N Engl J Med. 2013;369(26):2515-2524.
- Englund M, Guermazi A, Gale D, et al. Incidental meniscal findings on knee MRI in middle-aged and elderly persons. N Engl J Med. 2008;359(11):1108-1115.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.