The cartilage in your knee is a crescent shaped disc called the meniscus, that acts as a 'shock absorber' in your knee.
The meniscus is a commonly injured structure in the knee. The injury can occur in any age group. In younger people, the meniscus is fairly tough and rubbery, and tears usually occur as a result of a forceful twisting injury. The entire inner rim of the medial meniscus can be torn in what is called a bucket handle tear. The meniscus can also have a flap torn from the inner rim.
The meniscus grows weaker with age, and meniscal tears can occur in aging adults as the result of fairly minor injuries, even from the up-and-down motion of squatting. Most often, there isn't one specific injury to the knee that leads to the degenerative type of meniscal tear. These tears of the menisci are commonly seen as a part of the overall condition of osteoarthritis of the knee in aging adults. Degenerative tears cause the menisci to fray and become torn in many directions.
The most common problem caused by a torn meniscus is pain. The pain may be felt along the edge of the knee joint closest to where the meniscus is located. Or the pain may be more vague and involve the whole knee. The knee may swell, causing it to feel stiff and tight. This is usually because fluid accumulates inside the knee joint. This is sometimes called water on the knee. This is not unique to meniscal tears, since it can also occur when the knee becomes inflamed. The knee joint can also lock up if the tear is large enough. Locking refers to the inability to completely straighten out the knee. This can happen when a fragment of the meniscus tears free and gets caught in the hinge mechanism of the knee, like a pencil stuck in the hinge of a door. A torn meniscus can cause long term problems. The constant rubbing of the torn meniscus on the articular cartilage may cause the joint surface to become worn, leading to knee osteoarthritis.
Initial treatment for a torn meniscus focuses on decreasing pain and swelling in the knee. Rest and anti-inflammatory medications can help decrease these symptoms. You may need to use crutches until you can walk without a limp. Some patients may receive physiotherapy treatment for meniscal problems. Physiotherapists treat swelling and pain with the use of ice, electrical stimulation, and rest periods with your leg supported in elevation. Exercises are used to help you regain normal movement of joints and muscles.
If the knee keeps locking up and cannot be straightened out, surgery may be recommended as soon as reasonably possible to remove the torn part that is getting caught in the knee joint. But even a less severely torn meniscus may not heal on its own.
If symptoms continue after nonsurgical treatment, surgery will probably be suggested to either remove the torn portion of the meniscus (arthroscopic meniscectomy) or repair the meniscus (meniscal repair).