Knee Injuries

Overview :

Because the knee joint is both vulnerable and used extensively in many activities, it is prone to injuries. The American Academy of Orthopaedic Surgeons estimates that 19.5 million visits to doctors' offices in 2002 were for knee problems. In some sports including football, skiing, and gymnastics, and racket sports, injury rates to avid practitioners can near 50 percent, and knee injuries are the most common reason patients visit orthopedic doctors. An estimated one in five runners gets a knee injury. The majority of knee injuries, however, are minor and do not require intensive treatment.

The knee, the largest joint in the body, connects the thighbone (femur) to the lower leg (tibia). It is a complex and efficient joint consisting of ligaments, cartilage, and the bone of the kneecap (patella). All of these parts can be injured. Inside the knee joint is synovial fluid that protects and lubricates the parts, which during injuries may increase and cause swelling. The bursa are sacs in the knee that contain synovial fluid and provide cushioning and lubrication.

Four ligaments comprise the knee joint. The medial collateral ligament (MCL) runs along the inside of the knee, while the lateral collateral ligament (LCL) is on the outside of the knee. The cruciate ligaments cross inside the knee. The anterior cruciate ligament (ACL) is deep inside the knee and limits rotation of the joint. The posterior cruciate ligament (PCL) is also inside the knee and limits the backward movement of the joint. Ligaments in the knee can be partially or completely torn, depending on the extent of the injury.

The minisci cartilage are two thin, oval-shaped tissues that act as cushions between the ends of the leg bones. The medial miniscus is the cartilage closest to the other leg while the lateral miniscus is nearer the outside of the knee. Injuries to the minisci include tears from injuries and impact and degenerative wearing away of the structure. The minisci can be partially or completely torn during injury.

The bones around the knee, including the kneecap, can be broken, fractured, or chipped. The patellar tendon connects the kneecap to the shinbone, while the quadriceps tendon connects the quadriceps muscle to the patella. The patellar tendon can be torn or can develop injury and pain from degeneration. It can also be fully dislocated or partially dislocated (called subluxation). The tendons in the knee may develop pain and inflammation known as tendonitis.

The bones of the knee joint are covered with tissue known as articular cartilage. This cartilage can be injured or fractured, and can also develop a degenerative condition called chondromalacia. Osteoarthritis is the pain associated with the wearing down of this cartilage.