Knee Joint Cartilage Defects: Overview

Knee Joint Cartilage Defects: Overview

The knee is a major weight-bearing joint that supports the body during everyday movements. It is made up of three bones: the femur, or thigh bone; the tibia, or shinbone; and the patella, or kneecap. The ends of the femur and tibia, as well as the undersurface of the patella, are lined with articular cartilage.

Articular cartilage reduces friction with movement and allows the bones of the knee to glide smoothly as the joint bends and straightens. Damage to this cartilage affects the knee’s ability to move normally and support activity, often resulting in stiffness and pain. When cartilage wears down to the underlying bone, painful bone-on-bone friction can occur.

Widespread cartilage damage is commonly seen with osteoarthritis. In contrast, cartilage damage that occurs primarily in one area of the knee is referred to as an osteochondral defect, or cartilage defect.

Cartilage defects often result from a traumatic event, such as a fall or an injury where the knee is forcefully impacted or jammed in a straightened position. Dislocation of the kneecap is another common cause of cartilage damage.

Cartilage defects can also occur in association with other knee injuries. Injury to the medial collateral ligament, or MCL, or the lateral collateral ligament, or LCL, can create instability on one side of the knee. Twisting injuries, particularly those involving damage to the anterior cruciate ligament, or ACL, may also lead to instability.

When the knee is unstable or repeatedly gives way, cartilage surfaces may collide abnormally, resulting in further cartilage damage. In some cases, repeated stress over time can gradually break down a portion of the articular cartilage.

In athletic populations, cartilage defects most commonly develop along the patellofemoral surfaces, including the underside of the kneecap and the front portion of the end of the thigh bone. The femoral condyles are the next most common location, followed by the tibial plateau at the top of the shinbone.

Cartilage defects of the knee can produce a wide range of symptoms, including pain, swelling, instability, limited range of motion, difficulty bearing weight, locking, and clicking. Some patients may also experience the sensation that something is caught within the knee.

This sensation may be caused by a loose body, which is a fragment of cartilage or bone that has broken off and is floating within the joint.

To help establish a diagnosis, a health care provider will typically order imaging studies. X-rays are taken from multiple angles, including weight-bearing, side, and top-down views. An MRI may also be used to evaluate the cartilage in greater detail. These findings, along with the patient’s symptoms, help guide appropriate treatment recommendations.