Knee injuries are not unusual among people who are extremely active, especially those involved in sports. These injuries can be the result of a one-time traumatic event, or due to repetitive use of the knee. Injuries range in severity from minor strains to complete tears. Structures within the knee that are most commonly injured include ligaments, tendons and cartilage.
A fairly common example of a knee injury is damage to the anterior cruciate ligament, or ACL. The ACL is usually injured by a sudden twisting motion, which can often occur as the result of athletic activities or in some jobs that require a great deal of twisting.
Other knee ligaments that can suffer injury are the posterior cruciate ligament, called the PCL, and the medial and lateral collateral ligaments. The PCL can be injured by a direct blow to the knee, for example a front on tackle in football.
The medial and lateral collateral ligaments stabilize the knee, limiting side-to-side motion. The medial collateral ligament is often injured due to a blow to the outside of the knee, while the lateral collateral ligament is frequently injured by trauma to the inside of the knee.
Another common knee injury involves the meniscus. The meniscus is a C-shaped piece of cartilage that acts like a pad between the femur, or thigh bone, and tibia, or shin bone. The meniscus can be injured if the knee is twisted while bearing weight, and a partial or total tear can occur. A medial collateral ligament injury may also result in a tear in the medial meniscus. If the tear is small, the meniscus may heal without surgery. However, if the tear is large, a fragment of the meniscus may prevent normal movement of the knee, and surgery may be required.
An example of a repetitive injury to the knee is a condition called chondromalicia, or “runner’s knee.” Chondromalacia is due to an irritation of the undersurface of the kneecap. The undersurface of the kneecap, or patella, is covered with a layer of cartilage. This cartilage normally glides smoothly across the knee when the joint is bent. However, in some cases, the kneecap tends to rub against one side of the knee joint, and the cartilage surface becomes irritated, resulting in knee pain.
Tendons attach the muscles to the bone. Overusing a tendon, which happens frequently in some sports, can result in stretching and inflammation of the tendon. One example of this type of tendinitis is called “jumper’s knee.” In sports that require jumping, such as basketball, the tendon can become inflamed. More severe injuries to the tendon can result in a rupture or tear.