Cartilage Injuries

Articular cartilage is the smooth, white tissue that covers the ends of the bones where they meet in a joint. In the knee, it lines the end of the thigh bone (femur), the top of the shin bone (tibia), the back of the kneecap (patella), and the groove the kneecap glides in (trochlea). This tissue allows the bones to glide against each other with almost no friction and helps distribute load across the joint.

Articular cartilage has no blood supply. As a result, once it is damaged, it has very limited capacity to repair itself. When the body does attempt to fill a defect, it typically produces fibrocartilage, a scar-like tissue that is less durable than the original cartilage.

Types of Cartilage Injuries include:

Chondral defects

Damage limited to the cartilage layer, ranging from softening and fraying to a full-thickness defect that exposes the underlying bone.

Osteochondral defects

Injuries involving both the cartilage and the bone beneath it, often from a significant impact or a kneecap dislocation.

Osteochondritis dissecans (OCD)

A condition, most common in adolescents and young adults, in which a segment of bone beneath the cartilage loses its blood supply and can loosen or separate from the surrounding bone.

Degenerative cartilage loss

Gradual, widespread wear associated with arthritis. This differs from a focal defect, which is a well-defined area of damage surrounded by healthy cartilage, and the distinction has a major impact on treatment.

Cartilage injuries can result from a single event or from repetitive overload:

• Traumatic injury: A twisting injury, a hard landing, or a direct blow to the knee.
• Kneecap dislocation: Each dislocation can shear cartilage off the back of the kneecap or the end of the femur.
• Ligament injury: ACL tears and other instability allow abnormal shifting of the joint that damages cartilage, both at the time of injury and over time.
• Meniscus loss: Without a functioning meniscus, the cartilage beneath it absorbs far more load.
• Malalignment: A bowlegged or knock-kneed limb, or a poorly tracking kneecap, concentrates stress on one area of the joint.
• Osteochondritis dissecans: Believed to be related to repetitive stress and blood supply to the bone, often in young athletes.

Symptoms vary with the size and location of the defect. Some cartilage injuries cause few symptoms, while others significantly limit activity. Common symptoms include:

• Pain with activity: Aching during or after running, jumping, squatting, or climbing stairs, often localized to one area of the knee.
• Swelling: Recurrent swelling after activity, as the joint lining becomes irritated.
• Catching or locking: A loose fragment of cartilage or bone can move within the joint and cause catching or a knee that suddenly locks.
• Grinding or clicking: A sensation of roughness with movement.
• Stiffness: Reduced motion, particularly after rest or with swelling.
• Pain at the front of the knee: Cartilage damage behind the kneecap often causes pain with stairs, squatting, or prolonged sitting.

Diagnosis begins with a detailed history and physical exam. Dr. Rynecki Baker asks about how symptoms began, prior injuries or surgeries, and which activities cause pain. The exam assesses swelling, motion, areas of tenderness, ligament stability, kneecap tracking, and alignment, since cartilage injuries rarely occur in isolation.
Imaging defines the injury and the environment around it. X-rays evaluate joint space, arthritis, bone fragments, and osteochondritis dissecans lesions. Full-length standing x-rays measure overall limb alignment, which is critical when planning treatment for a defect on one side of the knee. MRI is the best tool for evaluating cartilage. It shows the size, depth, and location of a defect, the condition of the underlying bone, the stability of an OCD lesion, and associated injuries to the meniscus and ligaments.

Dr. Rynecki Baker considers the full picture, including the defect’s size and location, the patient’s age and activity level, and the health of the meniscus, ligaments, and alignment, before recommending a treatment plan.

Cartilage restoration is one of the most nuanced areas of sports medicine. Success depends not only on choosing the right procedure for the defect, but also on recognizing and correcting the factors that caused it, such as instability, meniscus loss, or malalignment. Dr. Rynecki Baker’s training at NYU Langone Health and Hospital for Special Surgery, along with her research in knee preservation and patellofemoral instability, means patients are cared for by a specialist with deep knowledge of how the knee works as a whole.