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Three bones make up the knee joint:

• the bottom part of the thighbone, called the femur
• the top part of the shinbone, called the tibia
• the kneecap, called the patella.

The ends of these bones are lined with articular cartilage, a smooth protective material that absorbs weight and pressure placed on the joint and helps the bones to move easily while the body is in motion. Meniscus is another form of cartilage found in the knee. Two crescent-shaped discs, the menisci, provide cushioning between the bottom of the femur and the top of the tibia.

Cartilage does not have the capacity to heal without treatment. Unlike muscle and bone, the tissue has no direct blood supply to carry it oxygen and vital nutrients, which would help it recover from injury. Damage to the articular knee cartilage can cause pain, inflammation, a clicking noise and catching sensation, and reduced range of motion of the joint. Cartilage injuries that are wider than a centimeter have the potential to get bigger over time, which may lead to osteoarthritis, a degenerative condition of the joint.

Causes of Knee Cartilage Injuries

Articular cartilage injuries of the knee may be caused by repetitive actions, a traumatic event such as a fall, or engaging in intense physical activity such as running. Articular cartilage can also be damaged through acute injury from participation in contact sports such as football, basketball, and hockey. Sometimes damage to articular cartilage occurs alongside other injuries of the knee, including meniscus tears and anterior cruciate ligament tears.

Your doctor may refer to the injury as a full-thickness lesion, meaning a cartilage injury that reaches the underlying bone, or a partial-thickness lesion, which goes partway into the articular cartilage.

�ٺ���Ƶ doctors conduct a comprehensive history and physical examination and use advanced imaging tests to diagnose knee cartilage injuries.

Medical History and Physical Examination

Your doctor asks about your symptoms and the impact that they have on your daily activities and ability to exercise. You may discuss what treatments you have tried and how they have impacted your symptoms and function. Your doctor then performs a thorough physical examination, looking for signs of swelling, assesses range of motion of the joint, and touches and presses on the knee to check for tenderness and pain.

Imaging Tests

Your doctor may order an X-ray to create images of the knee bones and to rule out other causes of your symptoms, such as fractures or degenerative osteoarthritis.

An MRI, which creates images of soft tissues, helps your doctor determine whether you have an acute injury to the knee cartilage. This sensitive imaging test allows the doctor to evaluate the size and depth of the cartilage injury, whether or not loose pieces of cartilage are floating in the joint, and the status of other important structures, including the meniscus and knee ligaments.