Cartilage Diseases: Types, Symptoms, Causes, and Treatments

What are the diseases of the cartilage?

Cartilage, a vital connective tissue, is susceptible to a range of diseases and conditions, primarily characterized by degradation, inflammation, or injury, leading to pain, reduced mobility, and impaired joint function.

Understanding Cartilage: The Foundation

Cartilage is a resilient, semi-rigid form of connective tissue found throughout the body, playing critical roles in support, flexibility, and shock absorption. Unlike bone, cartilage is avascular (lacks blood vessels) and aneural (lacks nerves), meaning it has limited capacity for self-repair once damaged.

There are three main types of cartilage, each with distinct properties and locations:

• Hyaline Cartilage: The most common type, found covering the ends of bones in joints (articular cartilage), in the nose, trachea, and ribs. It provides a smooth, low-friction surface for joint movement and acts as a shock absorber.
• Fibrocartilage: Strongest and most rigid, found in areas requiring high tensile strength and shock absorption, such as the intervertebral discs of the spine, menisci of the knee, and pubic symphysis.
• Elastic Cartilage: Highly flexible, found in the earlobes, epiglottis, and parts of the larynx, allowing for shape retention with significant flexibility.

Diseases of cartilage predominantly affect hyaline and fibrocartilage, given their roles in weight-bearing and joint articulation.

Common Diseases and Conditions Affecting Cartilage

Cartilage can be affected by various conditions, ranging from degenerative wear-and-tear to inflammatory and autoimmune disorders.

Osteoarthritis (OA)

Osteoarthritis is the most prevalent form of arthritis and a leading cause of disability worldwide. It is primarily a degenerative joint disease characterized by the breakdown of articular (hyaline) cartilage, particularly in weight-bearing joints like the knees, hips, spine, and hands.

• Mechanism: Over time, the smooth cartilage surface roughens and wears away, leading to bone-on-bone friction. This triggers bone spur formation (osteophytes) and inflammation of the joint lining (synovium).
• Causes: A combination of mechanical stress (wear and tear), genetic predisposition, age, obesity, previous joint injury, and repetitive joint loading.
• Symptoms: Joint pain (worsened by activity, relieved by rest in early stages), stiffness (especially after inactivity), swelling, tenderness, loss of flexibility, and a grating sensation or popping sound (crepitus).

Rheumatoid Arthritis (RA)

Rheumatoid arthritis is a chronic autoimmune disease where the body's immune system mistakenly attacks its own tissues, primarily the synovium (lining of the joints). While not a direct disease of cartilage, the chronic inflammation caused by RA leads to significant cartilage destruction.

• Mechanism: Inflamed synovium thickens and produces destructive enzymes that erode articular cartilage and underlying bone.
• Causes: Autoimmune response, genetic factors, and environmental triggers.
• Symptoms: Symmetrical joint pain, stiffness, swelling, and tenderness, often affecting smaller joints of the hands and feet first. Fatigue, fever, and loss of appetite are common systemic symptoms.

Traumatic Cartilage Injuries

Acute injuries can directly damage cartilage, especially fibrocartilage structures like the menisci in the knee or articular cartilage on joint surfaces.

• Examples:
  • Meniscal Tears: Common in the knee, often due to twisting or pivoting motions, especially in sports. Tears can be acute (traumatic) or degenerative.
  • Articular Cartilage Defects: Direct impact or sudden forceful movements can cause localized areas of cartilage to detach or become damaged, leading to pain, swelling, and mechanical symptoms like catching or locking.
• Causes: Direct trauma, sudden twisting, falls, or high-impact activities.
• Symptoms: Immediate pain, swelling, joint instability, catching or locking sensations, and difficulty bearing weight.

Chondromalacia Patellae

Chondromalacia patellae refers to the softening and breakdown of the articular cartilage on the underside of the kneecap (patella). It is particularly common in young athletes.

• Mechanism: Often results from patellar maltracking (the kneecap not gliding smoothly in its groove), leading to increased friction and stress on the cartilage.
• Causes: Muscle imbalances (e.g., weak quadriceps), overuse, improper biomechanics, trauma, or flat feet.
• Symptoms: Dull, aching pain around or behind the kneecap, especially when going up or down stairs, squatting, or prolonged sitting with bent knees. Crepitus may also be present.

Gout

Gout is a form of inflammatory arthritis caused by the accumulation of uric acid crystals (monosodium urate) in the joints. These sharp crystals can deposit in and damage articular cartilage.

• Mechanism: Urate crystal deposition triggers a severe inflammatory response, leading to acute, painful attacks. Chronic untreated gout can lead to extensive cartilage and bone erosion.
• Causes: High levels of uric acid in the blood (hyperuricemia), often due to diet, genetics, kidney issues, or certain medications.
• Symptoms: Sudden, severe attacks of pain, swelling, redness, and tenderness, often in the big toe, but can affect other joints.

Infectious Arthritis (Septic Arthritis)

Infectious (septic) arthritis is a joint infection caused by bacteria, viruses, or fungi. This is a medical emergency as the infection can rapidly destroy articular cartilage.

• Mechanism: Pathogens directly invade the joint space, leading to a severe inflammatory response and enzymatic degradation of cartilage.
• Causes: Spread of infection from other parts of the body (e.g., skin infection, UTI), direct inoculation (e.g., surgery, injection), or trauma.
• Symptoms: Sudden onset of severe joint pain, swelling, redness, warmth, fever, and chills.

Osteochondritis Dissecans (OCD)

Osteochondritis dissecans is a condition where a segment of bone and its overlying cartilage (osteochondral fragment) loses its blood supply, leading to its softening and potential detachment from the surrounding bone. It commonly affects the knee (femoral condyle), elbow, and ankle.

• Mechanism: Thought to be caused by repetitive microtrauma, ischemia (lack of blood supply), or genetic factors, leading to necrosis of the subchondral bone and subsequent cartilage damage.
• Causes: Often seen in adolescents and young adults involved in sports.
• Symptoms: Pain, swelling, joint locking, catching, weakness, and reduced range of motion.

Relapsing Polychondritis

Relapsing polychondritis is a rare, chronic autoimmune disease characterized by recurrent inflammation and destruction of cartilaginous tissues throughout the body.

• Mechanism: The immune system attacks cartilage in various locations, leading to inflammation, pain, and eventual degradation.
• Causes: Autoimmune, exact triggers unknown.
• Symptoms: Can affect cartilage in the ears (painful, swollen, reddened), nose (saddle nose deformity), joints (arthritis-like symptoms), trachea and bronchi (airway collapse), and eyes.

Factors Contributing to Cartilage Degradation

Several factors can increase the risk and progression of cartilage diseases:

• Age: Cartilage naturally loses some elasticity and water content with aging, making it more susceptible to damage.
• Genetics: Family history plays a role in conditions like osteoarthritis and rheumatoid arthritis.
• Obesity: Excess body weight significantly increases mechanical stress on weight-bearing joints, accelerating cartilage wear.
• Repetitive Stress/Overuse: Certain occupations or sports involving repetitive joint movements or high impact can contribute to cartilage breakdown over time.
• Trauma/Injury: Acute injuries, even if seemingly minor, can predispose a joint to accelerated cartilage degeneration in the future.
• Inflammation: Chronic systemic inflammation, whether from autoimmune diseases or metabolic conditions, can directly or indirectly damage cartilage.
• Nutritional Deficiencies: While less direct, severe deficiencies can impact overall tissue health and repair processes.

Diagnosis and Management Approaches

Diagnosing cartilage diseases typically involves a comprehensive approach:

• Physical Examination: Assessing joint pain, tenderness, swelling, range of motion, and stability.
• Imaging Studies:
  • X-rays: Can show joint space narrowing, bone spurs, and changes in bone structure, but don't directly visualize cartilage well.
  • Magnetic Resonance Imaging (MRI): Provides detailed images of soft tissues, including cartilage, menisci, and ligaments, making it excellent for detecting cartilage defects and inflammation.
  • Ultrasound: Can visualize joint effusion and some cartilage irregularities.
• Blood Tests: Used to rule out or confirm inflammatory or autoimmune conditions (e.g., rheumatoid factor, anti-CCP antibodies, uric acid levels, inflammatory markers).
• Joint Fluid Analysis (Arthrocentesis): Drawing fluid from the joint to check for crystals (gout), infection (septic arthritis), or inflammatory markers.

Management strategies vary widely depending on the specific disease, its severity, and the patient's overall health:

• Conservative Management:
  • Lifestyle Modifications: Weight loss, activity modification, assistive devices.
  • Physical Therapy: Strengthening surrounding muscles, improving joint mechanics, flexibility, and balance.
  • Medications: Pain relievers (NSAIDs), corticosteroids (oral or injected), disease-modifying anti-rheumatic drugs (DMARDs) for autoimmune conditions, uric acid-lowering drugs for gout.
  • Injections: Viscosupplementation (hyaluronic acid) for OA, platelet-rich plasma (PRP), or stem cell injections (still largely experimental for cartilage repair).
• Surgical Interventions:
  • Arthroscopy: Minimally invasive surgery to debride (clean out) damaged cartilage, remove loose bodies, or repair meniscal tears.
  • Cartilage Repair Procedures: Microfracture, osteochondral autograft transplantation (OATS), autologous chondrocyte implantation (ACI) for specific cartilage defects.
  • Osteotomy: Realignment of bone to shift weight off damaged areas.
  • Joint Replacement Surgery: For severe, end-stage cartilage destruction (e.g., total knee or hip replacement).

Prevention and Cartilage Health

While some cartilage diseases are unavoidable, several strategies can help maintain cartilage health and potentially slow progression:

• Maintain a Healthy Weight: Reduces stress on weight-bearing joints.
• Engage in Appropriate Exercise: Regular, low-impact activities (swimming, cycling, walking) strengthen muscles around joints without excessive impact. High-impact activities should be performed with proper form and progressive loading.
• Practice Proper Biomechanics: Ensure correct form during exercise and daily activities to minimize undue stress on joints.
• Prevent Injuries: Use proper safety equipment during sports, warm up adequately, and listen to your body to avoid overtraining.
• Balanced Nutrition: A diet rich in anti-inflammatory foods, antioxidants, and essential nutrients supports overall joint health. Adequate hydration is also crucial for cartilage integrity.
• Manage Chronic Conditions: Effectively managing underlying conditions like diabetes, gout, or autoimmune diseases can prevent secondary cartilage damage.

Understanding the various diseases that affect cartilage is crucial for early detection, appropriate management, and maintaining long-term joint health and mobility.