Knee Cartilage Injuries
There are three bones that make up the knee joint – the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). Articular cartilage covers both the bones and functions to reduce friction for smooth joint movement.
A cartilage defect refers to a specific, localized area of damage to the articular cartilage that lines the ends of the bones (like a tile missing in the floor). Cartilage allows for a smooth motion of two ends of the bones (for example thighbone and shin bone at the knee). It is a common injury affecting 5-10% of people over age 40, but it can also affect young patients who experience traumatic injuries.
Focal cartilage damage is typically caused by an acute traumatic injury such as a sudden pivot or twist with a bent knee, or a fall or direct blow to the knee. When the underlying bone beneath the cartilage is also damaged it is called an osteochondral injury.
Cartilage injuries can be classified as focal or diffuse. Diffuse cartilage damage (osteoarthritis) involves thinning of the cartilage in a large area. In a focal defect, only one portion of the cartilage is affected but the rest is relatively healthy (similar to a pothole in the street). Focal chondral defects are graded by severity. Grade I is the mildest and grade IV is the most severe describing full-thickness injury of the cartilage.
Cartilage does not have nerves and therefore does not cause pain when damaged. However, irritation of the bone beneath the cartilage or the lining of the joint (synovium) that results from cartilage loss can cause pain. Symptoms can vary depending on how much cartilage is injured. The bigger the lesion the more chances a patient can experience locking, catching or grinding sensation.
- Joint Pain: A focal cartilage defect typically causes pain in the knee joint. The pain is typically a dull ache, with intermittent sharp pain, felt on either side of the knee or in the front of the knee. The pain often worsens with activity and improves with rest.
- Stiffness: People with a focal cartilage defect may experience stiffness in the knee joint, making it difficult to move the knee through its full range of motion.
- Reduced range of motion: As the condition progresses, the range of motion in the knee joint may become limited, making it challenging to perform activities like walking, bending, or climbing stairs.
- Crepitus: Some people with a cartilage defect may notice a grinding or grating sensation in the knee joint, which is known as crepitus.
- Catching/locking: Catching or locking of the knee joint can occur in cases where a loose body of cartilage is present within the knee joint or when the cartilage defect is large
- Swelling
Physical Exam
A comprehensive physical exam will be conducted to assess the range of motion in your knee joint, look for signs of inflammation or swelling, and feel for areas of tenderness or crepitus (grating or grinding sensations). Your gait (the way you walk) will also be evaluated to identify any abnormalities.
Imaging
Diagnostic imaging is necessary to definitively diagnose a focal cartilage defect of the knee. X-rays will allow Dr. Chahla to assess the degree of remaining joint space, the extent of cartilage damage, and possible subchondral involvement. Dr. Chahla will also recommend an MRI of the knee to further assess the size and extent of the focal cartilage defect, subchondral involvement, and any possible concomitant injuries to the meniscus or surrounding structures.
Diagnostic Knee Arthroscopy
The most reliable diagnostic tool is a diagnostic knee arthroscopy, in which Dr. Chahla uses a small camera inserted into the knee joint. This allows Dr. Chahla to accurately assess and measure the lesion or biopsy it if further treatment is needed down the line.
At a Glance
Dr. Jorge Chahla
- Triple fellowship-trained sports medicine surgeon
- Performs over 700 surgeries per year
- Assistant professor of orthopedic surgery at Rush University
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