Knee Cartilage Tears: Types, Symptoms, Diagnosis, Treatment, and Outlook

What Happens When You Tear Cartilage in Your Knee?

When cartilage in the knee is torn, it disrupts the joint's smooth function, leading to pain, swelling, and mechanical symptoms, often progressing to long-term issues like osteoarthritis due to the tissue's limited healing capacity.

Understanding Knee Cartilage

The knee is a complex hinge joint, crucial for movement and weight-bearing. Its smooth operation relies heavily on specialized cartilage structures:

• Menisci (Fibrocartilage): There are two C-shaped menisci (medial and lateral) located between the femur (thigh bone) and tibia (shin bone). These are made of fibrocartilage, a tough, flexible tissue.
  • Function: They act as shock absorbers, distributing weight across the joint, enhancing joint stability, and facilitating lubrication.
• Articular Cartilage (Hyaline Cartilage): This smooth, glistening tissue covers the ends of the femur, tibia, and the back of the patella (kneecap). It's a type of hyaline cartilage.
  • Function: It provides a low-friction surface, allowing bones to glide effortlessly against each other during movement, and also helps distribute loads.

When either of these vital cartilages sustains damage, the knee's intricate biomechanics are compromised, leading to significant symptoms and potential long-term degeneration.

Types of Knee Cartilage Tears

Tears can affect either the menisci or the articular cartilage, each with distinct implications.

• Meniscus Tears: These are the most common type of knee cartilage injury. They often occur due to twisting motions while the foot is planted, direct impact, or simply through degenerative changes in older individuals.
  • Common Mechanisms: Sudden pivoting, deep squatting, kneeling, or direct impact.
  • Types of Tears: Meniscus tears can vary in pattern (e.g., radial, flap, horizontal, bucket-handle) and location (e.g., red zone, white zone), which impacts healing potential.
• Articular (Hyaline) Cartilage Damage: Unlike meniscus tears, damage to articular cartilage is often referred to as a "defect" or "lesion." It can range from softening (chondromalacia) to full-thickness loss exposing the underlying bone (osteochondral defect).
  • Common Mechanisms: Acute trauma (e.g., direct blow, dislocation), repetitive stress, or chronic wear and tear leading to osteoarthritis.
  • Progression: Articular cartilage has virtually no capacity for self-repair due to its avascular nature, meaning once damaged, it tends to progress, often leading to osteoarthritis.

Immediate Symptoms of a Knee Cartilage Tear

Upon tearing knee cartilage, individuals typically experience a range of immediate symptoms:

• Pain: Often localized to the joint line (for meniscus tears) or deep within the joint (for articular cartilage). It may worsen with certain movements like twisting, squatting, or weight-bearing.
• Swelling: Fluid accumulation within the joint (effusion) is common, occurring gradually over several hours after the injury.
• Stiffness: The knee may feel stiff, especially after periods of rest, and range of motion might be limited.
• Mechanical Symptoms: These are characteristic of cartilage tears:
  • Clicking or Popping: Audible sounds during movement.
  • Catching: A sensation of the knee "catching" or momentarily locking, preventing full extension or flexion.
  • Locking: The knee becoming stuck in a bent or straight position, requiring manipulation to free it. This is often due to a displaced fragment of cartilage.
• Instability: A feeling that the knee might "give way," particularly when weight-bearing or changing direction.

The Healing Process (or Lack Thereof)

A critical aspect of knee cartilage tears is their limited ability to heal, primarily due to their unique blood supply:

• Meniscus Healing Zones: The meniscus has varying healing potential based on its vascularity:
  • Red Zone (Outer Third): This area has a good blood supply, allowing for potential healing, especially if the tear is small and stable.
  • Red-White Zone (Middle Third): Has a limited blood supply, making healing less likely.
  • White Zone (Inner Third): This area is avascular (no blood supply) and therefore has virtually no capacity for self-repair. Tears in this zone typically do not heal spontaneously.
• Articular Cartilage Healing: Articular cartilage is completely avascular, aneural (no nerves), and alymphatic (no lymph vessels). This means it has an extremely poor capacity for self-repair. Damage often leads to the formation of fibrocartilaginous scar tissue, which is mechanically inferior to original hyaline cartilage and prone to further degeneration.

Diagnosis of a Knee Cartilage Tear

Accurate diagnosis is crucial for appropriate management:

• Clinical Examination: A healthcare professional will assess your symptoms, medical history, and perform specific physical tests:
  • Palpation: Checking for tenderness along the joint line.
  • Range of Motion: Assessing flexion, extension, and any mechanical blocks.
  • Special Tests: Maneuvers like the McMurray Test, Apley Compression Test, or Thessaly Test can help identify meniscus tears.
• Imaging Studies:
  • X-rays: Primarily used to rule out fractures or identify signs of osteoarthritis, but they do not show cartilage directly.
  • Magnetic Resonance Imaging (MRI): This is the gold standard for visualizing soft tissues like cartilage, ligaments, and tendons. An MRI can effectively identify the location, type, and severity of a cartilage tear.
• Arthroscopy (Diagnostic): In some cases, a surgeon may perform a diagnostic arthroscopy, where a small camera is inserted into the joint to directly visualize the cartilage and confirm the diagnosis.

Treatment Options

Treatment for a knee cartilage tear depends on the type, size, location of the tear, the patient's age, activity level, and overall knee health.

• Conservative Management: Often the first line of treatment, especially for smaller, stable tears or those in the vascular "red zone."
  • R.I.C.E. Protocol: Rest, Ice, Compression, Elevation.
  • Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): To manage pain and inflammation.
  • Physical Therapy: Strengthening exercises (quadriceps, hamstrings, glutes), range of motion exercises, proprioception training, and activity modification to reduce stress on the knee.
  • Bracing: To provide support and limit certain movements.
• Surgical Interventions: Considered when conservative measures fail, for larger tears, or for tears causing significant mechanical symptoms (e.g., locking).
  • Arthroscopic Meniscectomy (Partial or Total): Removal of the torn portion of the meniscus. While effective in relieving symptoms, it increases the risk of future osteoarthritis by reducing the knee's natural shock absorption.
  • Arthroscopic Meniscus Repair: Suturing the torn edges of the meniscus back together. This is preferred when possible, especially for tears in the vascular "red zone," as it preserves the meniscus and its protective function. Rehabilitation is longer than meniscectomy.
  • Articular Cartilage Repair/Restoration Procedures: For articular cartilage defects, these include:
    • Microfracture: Small holes are drilled into the bone beneath the defect to stimulate new fibrocartilage growth.
    • Osteochondral Autograft Transplantation (OATS) / Mosaicplasty: Healthy cartilage and bone plugs are harvested from a non-weight-bearing area of the knee and transplanted into the defect.
    • Autologous Chondrocyte Implantation (ACI): Healthy cartilage cells are harvested, grown in a lab, and then reimplanted into the defect.

Long-Term Implications and Management

A torn knee cartilage, especially if not adequately managed, can have significant long-term consequences:

• Increased Risk of Osteoarthritis: The primary long-term concern. Loss of meniscus tissue or damaged articular cartilage leads to increased stress on the remaining joint surfaces, accelerating the wear and tear process.
• Chronic Pain and Dysfunction: Persistent pain, stiffness, and reduced functional capacity can impact daily activities and quality of life.
• Importance of Rehabilitation: Post-injury or post-surgery, a structured rehabilitation program is critical. It focuses on restoring strength, flexibility, balance, and proprioception to protect the joint and optimize function.
• Lifestyle Modifications: Maintaining a healthy weight, avoiding high-impact activities that exacerbate symptoms, and choosing joint-friendly exercises (e.g., swimming, cycling) can help manage symptoms and slow progression.
• Ongoing Management: Regular follow-ups with a healthcare provider, adherence to exercise programs, and potentially pain management strategies are often necessary for long-term knee health.

Prevention Strategies

While not all tears are preventable, several strategies can reduce the risk of knee cartilage injuries:

• Strength Training: Develop strong muscles around the knee, including quadriceps, hamstrings, and glutes, to provide dynamic stability to the joint.
• Proper Warm-up and Cool-down: Prepare muscles for activity and aid in recovery, improving joint flexibility.
• Correct Biomechanics and Technique: Learn and practice proper form for sports and exercises to avoid awkward movements that stress the knee.
• Appropriate Footwear: Wear shoes that provide good support and cushioning for your activity.
• Listen to Your Body: Avoid pushing through pain, especially sharp or sudden pain, during physical activity. Allow adequate rest and recovery.
• Maintain a Healthy Weight: Excess body weight significantly increases the load on knee joints, accelerating wear and tear on cartilage.