The injury can be an overstretching of one or more ligaments, a tear of one or more ligaments, or an overstretching and a tear. Ligaments are tough bands of tissue that hold two bones together. How bad a sprain is depends on whether the ligament is just stretched, torn completely, or just partially torn. Also, the more ligaments involved, the more severe the injury. Most sprains are minor injuries.

Like a sprain, a strain involves an overstretch or a complete or partial tear, but of a muscle or tendon instead of a ligament. Tendons are similar to ligaments in that they are tough bands of tissue, but they attach a muscle to a bone instead of holding two bones together. Like sprains, most strains are minor injuries.

The most common site is the ankle. In fact, ankle sprains are the most common injury in the U.S. An ankle sprain most often occurs when the foot turns inward as a person runs, turns, falls, or lands on the ankle after a jump. This type of sprain is called an inversion injury. It sprains the ligaments on the outside of the ankle.

A sprain can also occur when you fall and land on an outstretched arm, or twist the knee when your foot is already planted on the ground. In sports, sliding into base or getting a blow to the body that forces a joint out of its normal position can also result in a sprain. Any event that forces a joint from its normal position can overstretch or tear a ligament.

This doesn't happen in all cases. Usual symptoms of a sprain include pain, swelling, and bruising at the joint. You may not be able to move the joint or it may be very painful to move it. The symptoms vary in intensity, depending on the severity of the sprain.

Other times to see your healthcare provider for a sprain:

• The injured joint is tender to touch.
• The injured area looks crooked or has bumps not visible on an uninjured joint.
• Your leg buckles when you try to use your injured knee or ankle.
• The injured area is numb.
• The injured area has been injured in the past.

Another common site is the hamstring muscle, at the back of the thigh. People who play contact sports such as soccer, football or hockey are at risk for strains. Hand and forearm strains are more common among people who play tennis, row or golf. Elbow strains can occur if you play racquet sports. Overuse of a joint can result in a chronic strain. For a chronic strain, the damage accumulates slowly, rather than all at once as in a fall or a blow to the joint.

Other symptoms include pain and muscle weakness. At the site of the injury, there may be swelling, cramping or inflammation. A severe strain involving a muscle or tendon tear can be very painful and disabling.

You should follow the RICE (rest, ice, compression, elevation) treatment for the first 1 to 2 days after the injury:

• Rest the injured joint.
• Put an ice pack on it. Wrap the ice pack in a thin towel. Use the ice pack 4 to 8 times a day for 20 minutes each time.
• Wrap the joint with a compression bandage.
• Raise it above the level of your heart.

Your healthcare provider may recommend a nonsteroidal anti-inflammatory medicine such as ibuprofen to help ease pain and swelling. A moderate to severe sprain or strain may need a cast or brace to hold the joint still while it heals. A severe sprain or strain may need surgery to fix the tear. How long it takes a sprain or strain to heal depends on how severe the injury is. A moderate ankle sprain might need up to 6 weeks to heal. A severe sprain might take 6 months to a year.

Other ways to prevent sprains and strains include maintaining a healthy weight; avoiding falls by keeping walkways in and around your home clear of clutter and by using sand or salt on icy patches in the winter; and wearing protective equipment when a playing a sport that puts you at risk for a sprain or strain.