The knee joint is one of the most easily injured joints in the body. Knee pain is a common reason for visits to a doctor or the emergency room, according to MayoClinic.com. One in three people aged 45 or older reports some type of knee pain. The knee is a complicated structure that includes four different bones and many ligaments, tendons and muscles. The frequency of use and the complexity of the structure make it easy to injure.
Trauma
One type of injury to the knee is trauma of some sort. This may come from a sports injury, slipping on the ice or an automobile accident. In each situation, a sudden quick twisting or a sharp blow to the knee can cause damage to ligaments, muscles and even nerves. Ligaments are thick bands of tissue that connect the bones together. There are many different ligaments in the knee that can be torn in trauma. Deep inside the knee are the anterior and posterior cruciate ligaments, or ACL and PCL. These ligaments can easily be torn in many different sporting situations and can end an athlete's career.
Osteoarthritis
According to The American Academy of Orthopaedic Surgeons, osteoarthritis of the knee is one of the five leading causes of disability among elderly men and women. Normally, the surfaces of the knee joint are covered with an articular cartilage that allows for smooth movement. Osteoarthritis destroys this cartilage and causes bones to rub directly on other bones during movement. Eventually this causes the joint to wear out and become destroyed. Because of the additional stress on the bones of the joint, they thicken and develop bone spurs. Some common symptoms involved with osteoarthritis of the knee are pain, stiffness, loss of range of motion and grinding or crackling noises with movement.
Rheumatoid Arthritis
Rheumatoid arthritis, or RA, is a chronic inflammatory condition that affects the entire body. It causes inflammation of the synovial lining of joints and is common in the knee. The American Academy of Orthopedic Surgeons says that RA usually affects both knees, as opposed to osteoarthritis, which will often affect only one. As the disease progresses, the synovial lining of the joints thickens and is destroyed. It leads to bone erosions and joint deformation.
Repetitive Stress
Activities that are repetitive in nature and stressful on the biomechanics of the knee can cause injury to muscles, ligaments and joints surfaces. One particular condition that can cause injury is IT band syndrome. The IT band is a thick ligamentous bands that runs down the lateral portion of the thigh and several muscles connect to it. When it becomes overused and stressed, the band thickens and becomes inflamed, leading to pain in the knee joint, according to Rice University. Over time, the altered biomechanics of the tight IT band can cause joint destruction and lead to osteoarthritis. Most repetitive stress injuries can be avoided by ensuring proper training, stretching and good biomechanics.
