About Knee Sprains

The knee is one of the most complicated joints in the body. Injury to any one of the ligaments can cause a knee sprain. The type and degree of a knee sprain depends on the location and severity of the injury. Knee sprains are one of the most common types of sports injuries, often ending the careers of professional athletes.

Misconceptions

• A sprain is not the same as a strain. A strain is a type of injury that occurs in the muscle or in the tendon that attaches the muscle to a bone. A sprain is a type of injury that happens to a ligament. Ligaments are similiar in appearance and composition to a tendon, but do not attach to a muscle. Ligaments only attach bone to bone and are primarily used to stabilize a joint, rather than to move it.

Identification

• Ligaments are the strong, fibrous bands that connect bone to bone to help control the direction and degree of movement in a joint. There are four ligaments that stabilize the knee joint. The anterior cruciate ligament, or ACL, restrains the forward motion of the shin. The posterior cruciate ligament, or PCL, prevents the shin bone from sliding too far backward. The medial collateral ligament, or MCL, runs along the inside of the knee joint, while the lateral collateral ligament, or LCL, runs along the outside of the knee; these two ligaments prevent side-to-side sliding of the thigh over the shin bone.

Types

• There are four degrees of sprains. The first degree involves only the overstretching of the ligament that may or may not result in a minor tear. The second-degree sprain is a tear in the ligament that is severe, but does not completely tear the ligament into two parts. The third-degree sprain is when the ligament is completely ruptured. The fourth sprain breaks the ligament and damages the bone the ligament was attached to.

Function

• The most common type of knee sprain is called an ACL injury. The injury occurs when the knee is forced backward, either in one major incident or with repetitive movements that wear down the ligament over time. When the ACL is sprained, it causes the knee the give out and allows the knee joint to slide. The instability makes pivoting motions difficult. Any athlete that needs to be able to make sudden turns needs a functioning ACL. Women tend to be eight times more likely to sustain an ACL injury than men. Rehabilitation and often surgery is needed to repair ACL sprains.

  PCL sprains are less common and often go undiagnosed. These injuries occur when the knee is forced to flex beyond its normal range of motion. Falling onto the knees can cause the PCL injury. Like the ACL sprain, a PCL causes the knee joint to become unstable. PCL sprains are usually treated with rehabilitation. Surgery is only considered if other structures of the knee have been damaged as well.

  MCL sprains occur when something impacts the outside of the knee, causing the knee to angle medially. This is frequently seen in football when an athlete gets clipped in the knee. Usually if the MCL is sprained, one or more of the other ligaments are damaged as well. Surgery is almost never done for an MCL sprain, but rehabilitation is extensive and can take as long as four months.

  The LCL is almost never injured in a knee sprain.

Prevention/Solution

• To avoid knee sprains, warm-up and cool-down stretches are important. Protective gear and wraps can help to stabilize the knee joints during sports. Strength and flexibility training also can prevent knee injuries by making the ligaments more resilient to injury.

Warning

• After a knee sprain occurs the first course of treatment is referred to as RICE: rest, ice, compression and elevation. The swelling can take a few days to subside. Evaluation by a doctor will determine which ligaments were injured and to what degree. Immobilization with a cast of bandage until the injury heals is the next step. Rehab follows once the injury has had a chance to heal.