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A sprained ankle with bruising.
A sprain is an injury in a joint, caused by the ligament being stretched beyond its own capacity. A muscular tear caused in the same manner is referred to as a strain. In cases where either ligament or muscle tissue is torn, immobilization and surgical repair may be necessary. Ligaments are tough, fibrous tissues that connect bones to other bones. Sprains can occur in any joint but are most common in the ankle and wrist.
- Decreased ability to move the limb
- If the ligament is ruptured, one may hear a popping sound
- Difficulty using the affected extremity
- First degree sprain - is a tear of only a few fibers of the ligament.
- Second degree sprain - is a tear of part of a ligament, from a third to almost all its fibers.
- Third degree sprain - is a complete tear of the ligament.
The diagnosis of a sprain injury is made by a physical examination. In most cases an x-ray (or stress x-ray) of the affected joint is obtained to ensure that there are no fractures. If a tear in the ligament is suspected, then an MRI or arthroscopy is obtained. MRI is usually ordered after swelling has subsided and can readily identify the presence of a ligament injury.
Sprains typically occur when the joint is overextended. This can cause over stretching of the joints, tear or slipping of the ligament.
Joints involved 
Although any joint can experience a sprain, some of the more common include:
- The ankle. It is the most common, and has been said that sprains such as serious ankle sprains are more painful and take longer to heal than actually breaking the bones in that area. See sprained ankle for more details.
- The knee. Perhaps one of the more talked about sprains is that to the anterior cruciate ligament (ACL) of the knee. This is a disabling sprain common to athletes, especially in American football, football (soccer), basketball, pole vaulting, softball, baseball and some styles of martial arts. See Anterior cruciate ligament injury.
- The fingers.
- The wrist.
- The toes.
Risk factors 
There are certain factors which increase risk of sprains. Fatigue of muscles generally leads to sprains. When one suddenly starts to exercise after a sedentary lifestyle, sprains are quite common. While scientific studies are lacking, it is often thought that not warming-up is a common cause of sprains in athletes. Warming-up is thought to loosen the joint, increases blood flow and makes the joint more flexible.
Diagnosis of sprains is not difficult but in most cases X-rays are obtained to ensure that there is no fracture. In many cases, if the injury is prolonged, magnetic resonance imaging (MRI) is performed to look at surrounding soft tissues and the ligament.
The first modality for a sprain can be remembered using the acronym RICE. The treatment of sprains depends on the extent of injury and the joint involved. Medications like non-steroidal anti-inflammatory drugs can relieve pain. Weight bearing should be gradual and advanced as tolerated.
- Rest: The sprain should be rested. No additional force should be applied on site of the sprain. In case of, for example, a sprained ankle, walking should be kept to a minimum.
- Ice: Ice should be applied immediately to the sprain to reduce swelling and pain. It can be applied for 10–15 minutes at a time (longer application of ice may cause damage instead of healing), 3-4 times a day. Ice can be combined with a wrapping to minimize swelling and provide support.
- Compression: Dressings, bandages, or ace-wraps should be used to immobilize the sprain and provide support. When wrapping the injury, more pressure should be applied at the far end of the injury and decrease in the direction of the heart; the reason for this is that it more easily causes unnecessary fluid to be flushed back up the blood stream in order to be recycled. Compression should not cut off the circulation of the limb.
- Elevation: Keeping the sprained joint elevated (in relation to the rest of the body) will also help minimize swelling.
Ice and compression (cold compression therapy) will not completely stop swelling and pain, but will help to minimize them as the sprain begins to heal itself. Careful management of swelling is critical to the healing process as additional fluid may pool in the sprained area.
The joint should be exercised again fairly soon, in milder cases from 1 to 3 days after injury. Special exercises are sometimes needed in order to regain strength and help reduce the risk of ongoing problems. The joint may need to be supported by taping or bracing, helping protect it from re-injury.
Functional rehabilitation 
Prolonged immobilization delays the healing of a sprain, as it usually leads to muscle atrophy and stiff joint. The components of an effective rehabilitation for all sprain injuries include increasing range of motion and progressive muscle strengthening exercise. These should be taken care of without delay.
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