A healthy meniscus acts as a shock absorber and provides a smooth surface for your knee to glide on. A tear in the meniscus prevents your knee from rotating, causing pain and locking. Injuries to the meniscus are common, particularly among athletes.
The meniscus is a structure in the knee joint that spans and cushions the space between the femur (thighbone) and the tibia (shinbone). There are two menisci in each knee – one on the inside (the medial meniscus) and one on the outside (the lateral meniscus).
Each is made of strong fibrocartilage and is shaped like a crescent or the letter “C.” These menisci look like suction cups that are carefully molded to the shape of the joint surfaces of the femur and tibia.
The shape and size of the meniscus allows it to serve several functions. When you stand up, your weight is borne evenly through your legs and down to your knees. The stress this weight places on the knee becomes even higher while walking, running and jumping. The meniscus functions as cushion to keep the bones of the knee joint from grinding against one other and causing damage. It also transmits the load of your weigh evenly across the knee joint. This load-sharing helps to prevent knee injuries and is extremely important to the function and health of the knee.
An injury to the meniscus can affect the knee’s ability to function normally. The most common type of meniscus injury is a meniscal tear.
There are two basic types of meniscal tears. A traumatic meniscal tear often happens when an athlete quickly turns the body, pivoting on the knee while the foot is planted in place on the ground. A degenerative meniscal tear is caused by wear over time, and usually affects older people.
Traumatic tears in the meniscus usually occur during forceful twisting of the knee and are common among players of sports such as football, basketball and soccer, but they can occur during any activity involving knee twisting. Less often, repetitive kneeling or rising from a squatting position while lifting can lead to a tear.
Degenerative or atraumatic tears usually in older populations and are caused by biology and degeneration and breakdown of the meniscal structure. People with degenerative tears may have twisted their knee and accelerate the tear. However, the tear pattern in a degenerative tear is very different from that of a traumatic tear. This is important because the treatment for a degenerative tear may be very different from that of a traumatic tear.
The key symptom of a meniscus tear is pain in the knee joint. A locking or catching sensation may also be felt in the knee, and it will often become inflamed (swollen). There may also be a feeling of weakness in the leg and a sense of the knee buckling or “giving way.” This is because displaced, fragmented tissue from a torn meniscus and swelling in the knee can affect the thigh muscles that support knee function.
Pain is usually felt in the knee above the meniscus while bearing weight on the affected knee and/or when twisting, turning, or pivoting on the knee, such as while getting in and out of a car. Walking up or down stairs may be particularly painful, and may also cause increased swelling in the knee.
Your doctor will ask about your symptoms and the circumstances of your injury, and conduct a physical examination. Radiological imaging studies will be ordered to confirm a diagnosis: X-rays will help rule out fractures or other bone injuries as the cause of pain, and high-resolution magnetic resonance imaging (MRI) studies will help reveal the type and location of the tear.
If you suspect a meniscus tear, it is important to be evaluated by a physiatrist, primary care sports medicine physician, or an orthopedic surgeon who specializes in sports medicine. (Find a doctor at HSS who treats meniscal tears.)
The meniscus has a limited blood supply and, therefore has limited ability to heal on its own. Only the outer one-third of the meniscus contains blood vessels required for healing. This is known as the “red zone.” The inner two-thirds of the meniscus is avascular (meaning there is no blood supply) and is also known as the “white zone.” Most meniscus tears that affect the white zone cannot heal on their own.
Simple walking and other activities that do not require twisting, pivoting, rapid change of direction, etc., are generally well-tolerated after a meniscus tear. Tears can progress over time, but the rate of progression is generally gradual and highly variable. Pain is the guide. If a tear is being made worse, there will generally be associated symptoms of increased pain.
Untreated tears can progress and become worse over time. Progressive meniscus loss can increase the risk that a person will develop degenerative knee arthritis. It is important to get a diagnosis and seek treatment early.
Nonsurgical treatments, such as anti-inflammatory medications and rehabilitation with a physical therapist may help some people with a torn meniscus. Other patients will need surgery, usually either a trimming or repair of the meniscus. Treatments may also depend on whether the tear is traumatic or degenerative.
A non-operative physical therapy treatment program will often focus first on reducing pain and maintaining the full motion of the knee. Oral nonsteroidal anti-inflammatory medications (such as ibuprofen) may also be prescribed. After the initial injury pain has decreased and the knee motion is restored, treatment may move to muscle strengthening. Plasma-rich platelet (PRP) injections may be beneficial to some patients.
Degenerative tears may not have any separated meniscal fragments that are causing mechanical symptoms in the knee. These can often be treated without surgery through conservative treatment.
Fragmented degenerative tears and most acute, traumatic tears will need surgery.
If surgery is required, a knee arthroscopy is most common. Minimally invasive incisions in the knee will be made using an arthroscope (or “scope”), a fiberoptic camera fixed with specialized surgical instruments. These instruments allow careful trimming (removal) of the torn meniscal fragments or, for some cases, a repair of the meniscal tear with sutures.
Since the meniscus has an important role in the long term health and function of the knee, the surgeon will always attempt to retain and repair any part of the meniscus that has the blood supply and the potential to heal. Most meniscal tears occur in the “avascular” part of the meniscus and cannot be repaired. In this case, the torn portion of the meniscus is removed. If the tear is large and occurs in a part of the meniscus with a good blood supply, then a repair may be performed.
In some degenerative meniscus tears, a portion will fragment and this loose fragment will cause symptoms of knee catching or locking. These may require surgical treatment. However, repair is generally not an option, since in most cases, the degenerated meniscus fragment has poor vascular supply and is thus not amenable to repair. Surgical treatment most often involves removal of the torn piece.
In a knee arthroscopy, two small incisions will be made. An arthroscope (or “scope”) will be passed through one of these to deliver saline solution that will expand the knee joint. The scope’s camera allows the surgeon to see inside the joint.
A surgical instrument is then inserted in through the other incision to perform one of the two basic operative treatments for meniscus tears:
View animations of knee arthroscopy surgery to trim and repair a torn meniscus.
The time that may be required to achieve a complete recovery after surgery will depend on the injury and the extent of meniscal surgery necessary. If a meniscus tear is repaired, then limited weightbearing with crutches may be required for approximately four to six weeks. On the other hand, if the torn portion of the meniscus is removed, then protected weightbearing may only be required for a few days.
A well-directed rehabilitation plan is important to achieve an excellent result. The early rehabilitation will focus on achieving full knee motion and reducing the swelling from surgery. After this has been achieved, the primary focus will be on restoring muscle strength. The treating physician and physical therapist or athletic trainer will carefully guide the rehabilitation after surgery.
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