There are 2 meniscii (cartilage discs) in the knee. A torn meniscus is a common reason for patients to have a knee arthroscopy (keyhole surgery).
The meniscus can be torn with a simple twist while the knee is bent. Tears produce symptoms such as clicking, locking, pain localized to the joint line and swelling. Often the symptoms can be intermittent with periods of the knee feeling normal.
When a torn meniscus is suspected it can be diagnosed with a scan (MRI) or with an arthroscopy. The advantage of an arthroscopy is it allows the tear to be treated at the same time. A scan is best employed when the chance of a meniscal tear being present is less certain.
The meniscus can tear in a number of different patterns. At the time of arthroscopy there are three options for dealing with a tear.
1. Partial Menisectomy
The most common option is to remove the torn unstable fragments of meniscus but leave the stable parts. Complete recovery from a partial menisectomy takes 6 – 8 weeks but you can walk on the knee straight away and you usually only need crutches for 2 - 3 days. Most patients are 80 – 90% better by 10 days.
2. Meniscal Repair
Sometimes a torn meniscus is repairable. This is done by passing stitches through the tear. To tie the stitches a small 3cm incision is made on the side of the knee where torn meniscus is being repaired. Rehabilitation from a meniscal repair takes 4 – 6 months. After surgery a brace is worn for 6 weeks. The knee is held straight while mobilizing during this 6 week period. Extensive physiotherapy is need.
Most tears are not suitable for repair. The advantage of a repair is that some studies suggest that it may reduce the chance of developing arthritis latter in life when compared to partial menisectomy.
3. Meniscal Debridement
Occasionally small tears are stable and if located in certain parts of the meniscus have the potential to heal. By roughening the edges of the tear (debridement) healing is encourage. The rehabilitation following a debridement is the same as after a partial menisectomy.
A torn meniscus is not a life threatening condition and surgery is always optional, never essential. Most meniscal tears will not heal on their own because 2/3rds of the meniscus has no blood supply (this is why meniscal repairs and debridements are far less common than partial menisectomy). Because symptoms can be intermittent and minor a number of people elect to live with a tear rather than have surgery. The decision to proceed to surgery is the patients.