A torn meniscus is one of the most common knee injuries. Any activity that causes you to forcefully twist or rotate your knee, especially when putting your full weight on it, can lead to a torn meniscus.

Each of your knees has two C-shaped pieces of cartilage that act like a cushion between your shinbone and your thighbone (menisci). A torn meniscus causes pain, swelling and stiffness. You also might feel a block to knee motion and have trouble extending your knee fully.

Conservative treatment — such as rest, ice and medication — is sometimes enough to relieve the pain of a torn meniscus and give the injury time to heal on its own. In other cases, however, a torn meniscus requires surgical repair.

If you've torn your meniscus, you might have the following signs and symptoms in your knee:

• A popping sensation
• Swelling or stiffness
• Pain, especially when twisting or rotating your knee
• Difficulty straightening your knee fully
• Feeling as though your knee is locked in place when you try to move it
• Feeling of your knee giving way

When to see a doctor

Contact your doctor if your knee is painful or swollen, or if you can't move your knee in the usual ways.

A torn meniscus can result from any activity that causes you to forcefully twist or rotate your knee, such as aggressive pivoting or sudden stops and turns. Even kneeling, deep squatting or lifting something heavy can sometimes lead to a torn meniscus.

In older adults, degenerative changes of the knee can contribute to a torn meniscus with little or no trauma.

Performing activities that involve aggressive twisting and pivoting of the knee puts you at risk of a torn meniscus. The risk is particularly high for athletes — especially those who participate in contact sports, such as football, or activities that involve pivoting, such as tennis or basketball.

Wear and tear on your knees as you age increases the risk of a torn meniscus. So does obesity.

A torn meniscus can lead to a feeling of your knee giving way, inability to move your knee normally or persistent knee pain. You might be more likely to develop osteoarthritis in the injured knee.

A torn meniscus often can be identified during a physical exam. Your doctor might move your knee and leg into different positions, watch you walk and ask you to squat to help pinpoint the cause of your signs and symptoms.

Imaging tests

• X-rays. Because a torn meniscus is made of cartilage, it won't show up on X-rays. But X-rays can help rule out other problems with the knee that cause similar symptoms.
• MRI. This uses radio waves and a strong magnetic field to produce detailed images of both hard and soft tissues within your knee. It's the best imaging study to detect a torn meniscus.

Arthroscopy

In some cases, your doctor might use an instrument known as an arthroscope to examine the inside of your knee. The arthroscope is inserted through a tiny incision near your knee.

The device contains a light and a small camera, which transmits an enlarged image of the inside of your knee onto a monitor. If necessary, surgical instruments can be inserted through the arthroscope or through additional small incisions in your knee to trim or repair the tear.

Initial treatment

Treatment for a torn meniscus often begins conservatively, depending on the type, size and location of your tear.

Tears associated with arthritis often improve over time with treatment of the arthritis, so surgery usually isn't indicated. Many other tears that aren't associated with locking or a block to knee motion will become less painful over time, so they also don't require surgery.

Your doctor might recommend:

• Rest. Avoid activities that aggravate your knee pain, especially any activity that causes you to twist, rotate or pivot your knee. If your pain is severe, using crutches can take pressure off your knee and promote healing.
• Ice. Ice can reduce knee pain and swelling. Use a cold pack, a bag of frozen vegetables or a towel filled with ice cubes for about 15 minutes at a time, keeping your knee elevated. Do this every four to six hours the first day or two, and then as often as needed.
• Medication. Over-the-counter pain relievers also can help ease knee pain.

Therapy

Physical therapy can help you strengthen the muscles around your knee and in your legs to help stabilize and support the knee joint.

Surgery

If your knee remains painful despite rehabilitative therapy or if your knee locks, your doctor might recommend surgery. It's sometimes possible to repair a torn meniscus, especially in children and young adults.

If the tear can't be repaired, the meniscus might be surgically trimmed, possibly through tiny incisions using an arthroscope. After surgery, you will need to do exercises to increase and maintain knee strength and stability.

If you have advanced, degenerative arthritis, your doctor might recommend a knee replacement. For younger people who have signs and symptoms after surgery but no advanced arthritis, a meniscus transplant might be appropriate. The surgery involves transplanting a meniscus from a cadaver.

Avoid activities that aggravate your knee pain — especially sports that involve pivoting or twisting your knee — until the pain disappears. Ice and over-the-counter pain relievers can be helpful.

The pain and disability associated with a torn meniscus prompt many people to seek emergency care. Others make an appointment with their family doctors. Depending upon the severity of your injury, you might be referred to a doctor specializing in sports medicine or a specialist in bone and joint surgery (orthopedic surgeon).

What you can do

Before an appointment, be prepared to answer the following questions:

• When did the injury occur?
• What were you doing at the time?
• Did you hear a loud "pop" or feel a "popping" sensation?
• Was there much swelling afterward?
• Have you injured your knee before?
• Have your symptoms been continuous or occasional?
• Do specific movements seem to improve or worsen your symptoms?
• Does your knee ever "lock" or feel blocked when you're trying to move it?
• Do you ever feel that your knee is unstable or unable to support your weight?