The knee joint is a complex system of bones, cartilage, meniscus, tendons and ligaments. The stresses in weight load, impact, and repetitive motion make this joint particularly vulnerable to a wide variety of acute and chronic conditions. These conditions vary from inconsequential to serious, and may be associated with misalignment, repetitive motion, general wear, injury, trauma, and disease.
Knee Pain: Conditions Associated with Motion Activity
Even in healthy young individuals, adolescent knee pain is not uncommon, and not necessarily a sign of a serious abnormality. A number of factors may be involved, including a disproportionate development of the thigh muscle which supports the knee joint, lack of stretching before activity resulting in diminished flexibility, misalignment of the legs between the hips and the ankles, incorrect sports training or ill-fitting equipment, and excessive training or sports activities.
Injuries of the Knee

The knee is the largest and most complex joint in the body, and with its load-bearing and dynamic range of uses in anything from daily activities to weightlifting and extreme sports, it is particularly vulnerable to a variety of injuries.

Numerous sporting activities, which involve fast-passed activity or repetitive stresses on the knee joint can lead to “runner’s knee.” Runners knee, which is characterized by a dull aching pain located around the kneecap and is particularly painful when walking up or down stairs, kneeling, or squatting. The term “runner’s knee” refers to a group of conditions associated with sports or other motion activities. Common runner’s knee conditions include anterior knee pain syndrome, patellofemoral malalignment, and chondromalacia patella.

Ligament Injuries: In the knee joint, four ligaments joint the thigh bone (femur) to the lower leg bones (tibia and fibula). These ligaments are particularly susceptible to injury from high-strain motions common to sports activities, as well as impact injuries in contact sports such as football.

Three of the four ligaments are more commonly involved in knee join ligament injuries including the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL), followed by the posterior cruciate ligament (PCL).

Injuries to the ACL ligament can result from hard landings and sudden stops, and occasionally direct impact. MCL injuries primarily result from impact injuries to the outside of the knee in contact sports. PCL injuries are common with a direct impact to the front of the knee.
Torn Cartilage (Meniscus)

The meniscus is an elastic cartilage attached to the knee joint ligaments, which provides cushioning for the joint. This cartilage is susceptible to tearing under high-stress motion twists of the knee joint common in fast-paced sports. Direct impact may also be responsible for tears in the meniscus knee cartilage.

Treatment for ligament injuries in the knee joint may involve either surgical or non-surgical treatments. Accurate diagnosis by an orthopedic doctor, as well as the type and extent of the injury will dictate to best treatment approach available.

Disease Conditions of the Knee

Arthritis of the Knee
Arthritis affects both men and women. Approximately one in five Americans of all ages – half under fifty – may develop arthritis, and it leads the list of disabilities in the United States. The primary symptom of arthritis is the loss or degradation of joint cartilage, and subsequent response the body undertakes to attempt correction of the cartilage loss. The elasticity of cartilage provides an ideal surface cushioning within hard bone joints to allow smooth pain-free motion. Diminished or lost cartilage within a joint leads to rough painful motion of the joint. The body’s response to the loss of cartilage within a joint is to infuse the joint lining with fluid to compensate for the lost cushioning effect of the cartilage. However, that fluid ultimately produces joint swelling and stretching of the joint covering (capsule) both of which lead to a painful condition during motion as well as while at rest. Untreated, the joint will continue on a path of degradation, including bone deformation, still furthering the loss of motion and causing additional pain.