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Questions and Answers About Knee Problems

Savvy Consumer: Questions and Answers About Knee Problems
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Questions and Answers About KNEE PROBLEMS

National Institute of Arthritis and Musculoskeletal and Skin Diseases

This fact sheet contains general information about knee problems. It includes descriptions and a diagram of the different parts of the knee, including bones, cartilage, muscles, ligaments, and tendons. Individual sections of the fact sheet describe the symptoms, diagnosis, and treatment of specific types of knee injuries and conditions. (See table below.) Information is also provided on the prevention of knee problems.

What Causes Knee Problems?

Some knee problems result from wear of parts of the knee, such as occurs in osteoarthritis. Other problems result from injury, such as a blow to the knee or sudden movements that strain the knee beyond its normal range of movement.

How Can People Prevent Knee Problems?

What Kinds of Doctors Treat Knee Problems?

Extensive injuries and diseases of the knees are usually treated by an orthopaedic surgeon, a doctor who has been trained in the nonsurgical and surgical treatment of bones, joints, and soft tissues (for example, ligaments, tendons, and muscles). Patients seeking nonsurgical treatment of arthritis of the knee may also consult a rheumatologist (a doctor specializing in the diagnosis and treatment of arthritis and related disorders).

What Are the Major Structures of the Knee? What Do They Do?

The knee joint works like a hinge to bend and straighten the lower leg. It permits a person to sit, stand, and pivot. The knee is composed of the following parts (see diagram):

Structures of the Knee

Bones and Cartilage

The knee joint is the junction of three bones—the femur (thigh bone or upper leg bone), the tibia (shin bone or larger bone of the lower leg), and the patella (kneecap). The patella is about 2 to 3 inches wide and 3 to 4 inches long. It sits over the other bones at the front of the knee joint and slides when the leg moves. It protects the knee and gives leverage to muscles.

The ends of the three bones in the knee joint are covered with articular cartilage, a tough, elastic material that helps absorb shock and allows the knee joint to move smoothly. Separating the bones of the knee are pads of connective tissue called menisci, which are divided into two crescent-shaped discs positioned between the tibia and femur on the outer and inner sides of each knee. The two menisci in each knee act as shock absorbers, cushioning the lower part of the leg from the weight of the rest of the body, as well as enhancing stability.


There are two groups of muscles at the knee. The quadriceps muscle comprises four muscles on the front of the thigh that work to straighten the leg from a bent position. The hamstring muscles, which bend the leg at the knee, run along the back of the thigh from the hip to just below the knee.


Ligaments are strong, elastic bands of tissue that connect bone to bone. They provide strength and stability to the joint. Four ligaments connect the femur and tibia:

Other ligaments are part of the knee capsule, which is a protective, fiber-like structure that wraps around the knee joint. Inside the capsule, the joint is lined with a thin, soft tissue, called synovium.


Tendons are tough cords of tissue that connect muscle to bone. In the knee, the quadriceps tendon connects the quadriceps muscle to the patella and provides power to extend the leg. The patellar tendon connects the patella to the tibia. Technically, it is a ligament, but it is commonly called a tendon.

How Are Knee Problems Diagnosed?

Doctors use several methods to diagnose knee problems.


Cartilage Injuries and Disorders


Injuries to the Meniscus

Arthritis of the Knee

Ligament Injuries

Anterior and Posterior Cruciate Ligament Injury

Medial and Lateral Collateral Ligament Injury

Tendon Injuries and Disorders

Tendinitis and Ruptured Tendons

Medial and Lateral Collateral Ligament Injury

Osgood-Schlatter Disease

Iliotibial Band Syndrome

Other Knee Injuries

Osteochondritis Dissecans

Plica Syndrome

Other Sources of Information of Knee Problems


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