Knee Joint Cartilage Defects: Overview

Knee Joint Cartilage Defects: Overview

The knee is a major weight-bearing joint that supports the body with everyday movements. The knee is made up of 3 bones: the femur, or thigh bone; tibia, or shinbone; and patella, or kneecap. The ends of the femur and tibia, as well as the undersurface of the patella, are all lined with articular cartilage. This cartilage reduces friction with movement and helps the bones glide smoothly, allowing the knee to bend and straighten.

Damage to the articular cartilage affects the ability of the knee to move smoothly and support movement. This can result in stiffness of the joint as well as pain if the cartilage wears down to the underlying bone and creates bone-on-bone friction. Damage across most of the articular cartilage occurs with osteoarthritis, but cartilage damage that primarily occurs in one location is called an osteochondral defect, or cartilage defect.

Cartilage defect injuries commonly result from a traumatic event, such as a fall or an injury where the knee is impacted or jammed in a straightened position, causing forceful compression in the knee. Dislocating the kneecap is another cause of cartilage damage. Cartilage defects in the knee can also occur with other knee injuries. Injury to the MCL, the medial collateral ligament, or the LCL, the lateral collateral ligament, can cause instability on one side of the knee. Twisting injuries, especially when the ACL, or anterior cruciate ligament, is injured can also result in instability. If the knee is unstable or gives way, it can result in damage to the cartilage surfaces as they come into contact with one another.

Sometimes, cartilage defect injuries can occur with repeated stress that breaks down a portion of the articular cartilage over time. In athletic populations, the most common areas to develop a cartilage defect are the patellofemoral surfaces, which include the underside of the kneecap and front portion of the end of the thigh bone. The femoral condyles are the next most common at the end of the thigh bone, followed by the tibial plateau at the top of the shinbone.

Cartilage defects of the knee can produce a variety of different symptoms, including pain, swelling, instability, limited range of motion, difficulty bearing weight through the knee, locking, and clicking. There may also be the feeling that there is something stuck inside the knee causing irritation. This is referred to as a loose body, which is a piece of cartilage or bone that has broken off within the joint.

To help make a diagnosis, a health care provider will likely perform imaging studies. A multiview x-ray looks at the knee from different angles, including weight-bearing; a lateral, or side view; and a merchant, or top-down view. An MRI can also be used to examine the cartilage. On this MRI, there is cartilage damage at the end of the thigh bone, which causes the bright white bruising of the bone. A health care provider will use these findings, along with a patient's symptoms, to recommend the appropriate treatment options.