Cartilage is a smooth, lubricated tissue in joints that enables effortless movement and absorbs forces. When this specialized tissue completely erodes, a condition known as full thickness cartilage loss, it profoundly impacts joint function and mobility.
Understanding Cartilage and Full Thickness Loss
Cartilage is a resilient, smooth connective tissue covering bone ends in joints, such as the knee and hip. It provides a low-friction surface for bones to glide and distributes mechanical loads. This tissue, typically 2 to 4 millimeters thick, lacks blood vessels, nerves, and lymphatic tissue, relying on synovial fluid for nourishment. Its composition of water, collagen, and proteoglycans gives it viscoelastic properties, allowing it to withstand significant loads.
Full thickness cartilage loss occurs when the entire layer of articular cartilage wears away, exposing the underlying bone. This severe damage is a Grade IV defect, indicating complete erosion. In contrast, partial thickness loss affects only part of the cartilage layer, without exposing bone. Full thickness loss leads to direct bone-on-bone friction, causing significant pain and joint dysfunction.
Common Causes and Risk Factors
Full thickness cartilage loss often stems from osteoarthritis (OA), a degenerative condition where cartilage gradually wears down, exposing bone. OA commonly affects weight-bearing joints like the knees, hips, and hands.
Traumatic injuries, such as blows, twists, or falls, are another cause of cartilage damage, resulting in acute tears or detachment. Repetitive stress or overuse from continuous impact can also degrade cartilage. Inflammatory conditions like rheumatoid arthritis can cause cartilage destruction due to immune system attacks on the joint lining, leading to inflammation.
Several risk factors increase the risk of full thickness cartilage loss. Advancing age is a factor, as cartilage naturally degenerates. Obesity significantly increases mechanical load on weight-bearing joints, accelerating breakdown. Fat tissue also releases inflammatory substances that contribute to degradation. Genetic predisposition plays a role, as genetic factors influence osteoarthritis risk and cartilage repair ability.
Recognizing the Signs
Signs of full thickness cartilage loss include progressively worsening symptoms. Joint pain is a primary indicator, often intensifying with activity or weight-bearing.
Other symptoms include joint stiffness, especially after rest or in the morning. Swelling around the affected joint is common. A reduced range of motion can develop, making it difficult to fully bend or straighten the joint. Grinding, clicking, or popping sensations, known as crepitus, are often felt or heard during joint movement due to irregular surfaces. The joint may also feel unstable or prone to “locking” if loose cartilage fragments interfere with movement.
Diagnosis and Identification
Diagnosing full thickness cartilage loss involves a detailed medical history and a thorough physical examination. During the exam, doctors assess the affected joint for tenderness, swelling, range of motion limitations, and grinding or popping sounds. These assessments help pinpoint the issue’s location and nature.
Imaging tests are used to visualize joint structures and confirm damage. X-rays can reveal joint space narrowing, indicating cartilage loss, and may show bone spurs. While X-rays don’t directly show cartilage, they infer its absence by bone-on-bone contact. Magnetic Resonance Imaging (MRI) provides a detailed view of soft tissues, including cartilage, for precise assessment of defects. Computed tomography (CT) scans or arthroscopy, a minimally invasive surgical procedure inserting a small camera into the joint for direct visual assessment and immediate grading, may also be performed.
Management and Treatment Approaches
Managing full thickness cartilage loss involves conservative and, if needed, surgical interventions. Conservative measures include pain management with medications or injections, and physical therapy to strengthen muscles, improve flexibility, and restore mobility. Lifestyle modifications, especially weight management, reduce mechanical load and slow disease progression. Assistive devices like braces or canes can offload pressure. If conservative treatments fail, surgical options are considered.
Surgical interventions range from joint replacement, especially for severely damaged large joints like the knee or hip, to various cartilage repair procedures. Techniques include microfracture, creating small holes in the bone to stimulate new, less durable fibrocartilage growth. Autologous Chondrocyte Implantation (ACI/MACI) involves harvesting and reimplanting a patient’s own lab-cultivated cartilage cells. Another option is osteochondral autograft or allograft transfer, transferring healthy bone and cartilage plugs from a less weight-bearing area or a donor. Treatment choice depends on factors like age, activity level, defect size and location, and overall joint health.