Chondral Defects in the Knee

A chondral defect occurs when the articular cartilage in the knee joint is damaged or worn away in a specific area. This condition can be likened to a “missing tile on a floor”—a defect in the cartilage leaves the underlying bone exposed, leading to discomfort and joint instability. The damage is typically graded based on its severity:

• Grade I: Mild damage to the cartilage surface.
• Grade II: Partial thickness injury that extends into deeper layers of the cartilage.
• Grade III: Deep injury affecting more than 50% of the cartilage thickness.
• Grade IV: Full-thickness damage, exposing the underlying bone.

Chondral defects are particularly concerning because articular cartilage does not regenerate well on its own, making early diagnosis and treatment essential for preventing further complications, such as osteoarthritis.

The most common cause of a chondral defect is acute trauma to the knee. This can result from a sudden twist or pivot during sports, a fall, or a direct blow to the knee. In some cases, the injury can extend beyond the cartilage to include the underlying bone, leading to what is known as an osteochondral injury. Other contributing factors to chondral defects include:

• Repetitive stress on the knee joint due to sports or physical activity.
• Congenital defects that affect cartilage structure or function.
• Degenerative conditions like osteoarthritis, which cause gradual wear and tear of the cartilage over time.

Since articular cartilage is essential for smooth joint movement, any disruption can lead to significant symptoms. Common signs of a chondral defect in the knee include:

• Pain: Typically localized to the area of the cartilage injury, especially during activities that put stress on the knee.
• Joint stiffness: Difficulty moving the knee, especially after periods of inactivity or after waking up.
• Swelling: Intermittent swelling of the knee, which may worsen after physical activity.
• Catching or locking sensation: If a piece of damaged cartilage becomes loose within the joint, it can cause a “catching” or “locking” sensation when trying to move the knee.

Early intervention is important for managing symptoms and preventing further damage to the joint.

Diagnosing a chondral defect requires a combination of a thorough medical history, physical examination, and imaging techniques. During the initial consultation, a doctor will ask about the circumstances surrounding the injury, any ongoing pain, and the patient’s future activity goals. The physical exam will assess joint stability, range of motion, and gait, though these tests may not always reveal the full extent of cartilage damage.

Imaging tests such as X-rays can help rule out other conditions like arthritis or bone fractures. However, magnetic resonance imaging (MRI) is often more effective at detecting cartilage injuries. In some cases, a more definitive diagnosis can be made using knee arthroscopy—a minimally invasive procedure in which a small camera is inserted into the joint to directly visualize and assess the extent of the cartilage injury.