Tibial cartilage is the smooth, protective tissue covering the top surface of the shin bone (tibia) within the knee joint. This tissue is composed of a dense matrix of water, collagen, and proteins, with very few cells and no blood vessels or nerves. Its structure allows the knee to move with minimal friction, facilitating fluid motion during daily activities.
The Role of Tibial Cartilage in the Knee
The top of the tibia, known as the tibial plateau, is capped with a 2 to 4 mm thick layer of articular cartilage. This tissue serves two primary functions. First, it provides a slick, lubricated surface that allows the femur (thigh bone) to glide across the tibia as the knee bends and straightens. This quality is a result of its high water content and a lubricating protein.
Second, the tibial cartilage acts as a shock absorber. Its composition, which includes large molecules called proteoglycans, allows it to retain water and resist compressive forces during high-impact activities. It is important to distinguish this articular cartilage from the menisci, which are C-shaped fibrocartilage pads that sit between the bones and provide additional cushioning and stability.
Common Causes of Tibial Cartilage Damage
Damage to the tibial cartilage falls into two categories: acute injury or chronic degeneration. Acute traumatic injuries occur during sports or from accidents, such as a direct blow to the knee, a fall, or a sharp pivoting motion. These events can cause the cartilage to tear, create a fissure, or break off a piece, exposing the underlying bone.
The other pathway to damage is through gradual wear and tear, a process linked with osteoarthritis. Over time, factors such as age, genetics, excess body weight, or joint misalignment can lead to the progressive thinning of the cartilage. This degenerative process leads to increased friction and deterioration within the joint.
Symptoms of a Tibial Cartilage Injury
Pain is a common complaint, frequently described as a sharp, localized sensation during weight-bearing activities like climbing stairs. Swelling, or joint effusion, is also a frequent sign as the body responds to irritation within the knee. A symptom that points toward a cartilage injury is a mechanical sensation of catching, popping, or locking. These feelings can occur when a loose fragment of detached cartilage becomes lodged between the moving surfaces of the joint, physically blocking the knee’s motion.
Diagnosis and Treatment Pathways
Diagnosing tibial cartilage damage starts with a physical examination and a review of the patient’s symptoms. While an X-ray can rule out bone-related issues, a magnetic resonance imaging (MRI) scan is the most effective tool. An MRI provides detailed images of the knee’s soft tissues, allowing doctors to assess the location, size, and depth of the cartilage defect.
Once a diagnosis is confirmed, non-surgical approaches are the first line of defense, aimed at managing symptoms and slowing further damage. Common strategies include:
- Physical therapy to strengthen the muscles that support the knee.
- Activity modification to avoid painful movements.
- Weight management to lessen stress on the knee.
- Use of anti-inflammatory medications.
In some cases, injections such as corticosteroids to reduce inflammation or hyaluronic acid to improve joint lubrication may be recommended.
Surgical intervention is considered when conservative methods do not provide relief or for larger cartilage defects. The choice of procedure depends on the patient’s age, activity level, and the specific characteristics of the injury. One technique is microfracture, where small holes are created in the bone to stimulate the growth of new scar-like cartilage called fibrocartilage. For larger defects, an osteochondral autograft transplantation system (OATS) procedure involves transplanting small plugs of healthy cartilage and bone from a non-weight-bearing area of the knee to the damaged site. Another option is matrix-induced autologous chondrocyte implantation (MACI), a two-stage procedure that uses the patient’s own lab-grown cartilage cells to regenerate the tissue.