Meniscus tear

The meniscus is a crucial structure within the knee joint that plays a significant role in load distribution, shock absorption, and joint stability. Meniscus tears are a common knee injury, particularly among athletes and older adults with degenerative changes. Understanding the anatomy, function, and clinical implications of meniscus tears is essential for accurate diagnosis and effective management.

Anatomy and Function of the Meniscus

Structure of the Knee Joint

The knee joint is a hinge joint formed by the femur, tibia, and patella. It is stabilized by ligaments, tendons, and cartilage. The menisci are crescent-shaped fibrocartilaginous structures situated between the femoral condyles and the tibial plateau, providing cushioning and stability to the joint.

Medial and Lateral Menisci

There are two menisci in each knee: the medial meniscus and the lateral meniscus. The medial meniscus is C-shaped and firmly attached to the medial collateral ligament, making it less mobile. The lateral meniscus is more circular and mobile, allowing it to better accommodate joint movements. Both menisci work together to distribute load across the knee.

Role in Load Distribution, Shock Absorption, and Joint Stability

The menisci absorb compressive forces generated during weight-bearing activities, reducing stress on the articular cartilage. They also enhance joint stability by deepening the tibial articulating surfaces and facilitate smooth movement of the knee. Damage to the meniscus can compromise these functions, leading to pain, instability, and early degenerative changes.

Definition and Types of Meniscus Tears

Traumatic vs Degenerative Tears

Meniscus tears can be classified as traumatic or degenerative. Traumatic tears typically occur in younger individuals due to sudden twisting or impact during sports or accidents. Degenerative tears are more common in older adults and result from gradual wear and weakening of the meniscal tissue over time.

Common Tear Patterns

• Vertical/Longitudinal Tear: Runs along the length of the meniscus and may progress to a bucket-handle tear.
• Horizontal Tear: Splits the meniscus into upper and lower layers, often associated with degeneration.
• Radial Tear: Extends from the inner edge toward the periphery, disrupting hoop stress transmission.
• Flap or Complex Tear: Irregular tears with fragments that can interfere with joint movement and cause locking.

Etiology and Risk Factors

Sports and Physical Activities

Meniscus tears frequently occur during sports that involve sudden twisting, pivoting, or direct impact to the knee. Activities such as football, basketball, soccer, and skiing are common causes of traumatic meniscus injuries.

Age-related Degeneration

As people age, the meniscal tissue becomes less elastic and more prone to tearing. Degenerative tears often develop gradually in individuals over 40 and may be associated with minor movements or normal daily activities.

Pre-existing Knee Conditions

• Osteoarthritis: Degenerative changes in the joint increase stress on the meniscus, making it more susceptible to tears.
• Ligament Injuries (e.g., ACL tear): Damage to stabilizing ligaments can alter knee mechanics, increasing the risk of meniscus injury.

Pathophysiology

Mechanisms of Meniscus Injury

Meniscus tears result from either acute trauma or chronic degeneration. In traumatic cases, rotational forces or sudden impact cause the meniscal fibers to split. In degenerative cases, repetitive stress and reduced tissue elasticity lead to fraying and tearing over time.

Impact on Knee Biomechanics

Meniscus damage disrupts the normal distribution of load across the knee, leading to increased stress on the articular cartilage. This can result in joint instability, altered movement patterns, and accelerated cartilage wear.

Consequences of Untreated Tears

Untreated meniscus tears can lead to persistent pain, swelling, mechanical symptoms such as locking or catching, and progressive cartilage degeneration. Chronic meniscus injury increases the risk of developing osteoarthritis and long-term knee dysfunction.

Clinical Presentation

Symptoms

• Pain: Localized to the joint line, often worsened by twisting, squatting, or stair climbing.
• Swelling: May develop immediately or gradually after injury.
• Locking or Catching: A sensation of the knee getting stuck, often due to displaced meniscal fragments.
• Reduced Range of Motion: Difficulty fully bending or straightening the knee.

Physical Examination Findings

• Joint Line Tenderness: Pain elicited along the medial or lateral joint line on palpation.
• Positive McMurray Test: Pain or a clicking sound during rotation of the flexed knee indicating meniscus injury.
• Thessaly Test: Pain or locking when the patient stands on one leg and rotates the knee, suggestive of meniscal tear.

Diagnosis

Imaging Studies

• MRI: The gold standard for detecting meniscus tears, providing detailed visualization of meniscal structure and associated injuries.
• X-ray: Helps rule out fractures or advanced arthritis, but does not show meniscal tears directly.
• Ultrasound: Limited use, mainly for detecting peripheral or displaced meniscal fragments.

Arthroscopy

Arthroscopy is a minimally invasive procedure used both for diagnosis and treatment. It allows direct visualization of the meniscus and enables simultaneous repair or partial meniscectomy if indicated.

Treatment and Management

Conservative Management

• Rest, Ice, Compression, Elevation (RICE): Initial management to reduce pain and swelling.
• Physical Therapy: Exercises to restore range of motion, strengthen surrounding muscles, and improve joint stability.
• Activity Modification: Avoiding activities that exacerbate symptoms until healing occurs.

Surgical Management

• Meniscus Repair: Suturing the torn meniscal tissue to promote healing, preferred in younger patients with tears in the vascular zone.
• Partial Meniscectomy: Removal of the damaged portion of the meniscus when repair is not feasible, preserving as much tissue as possible.
• Total Meniscectomy: Rarely performed due to increased risk of early osteoarthritis and long-term joint degeneration.

Rehabilitation and Recovery

Post-treatment rehabilitation focuses on gradual restoration of knee strength, flexibility, and function. Recovery timelines vary depending on the type of treatment, tear location, and patient age, ranging from a few weeks for minor tears to several months for repaired tears.

Prevention

Strengthening Exercises

Regular exercises targeting the quadriceps, hamstrings, and hip muscles improve knee stability and reduce the risk of meniscus injury.

Proper Techniques in Sports

Using correct techniques during running, jumping, pivoting, and landing helps minimize excessive rotational forces on the knee.

Joint Protection Strategies

Maintaining a healthy body weight, wearing supportive footwear, and avoiding repetitive high-impact movements can decrease stress on the meniscus and prevent injury.

Prognosis

Factors Affecting Healing

The prognosis of a meniscus tear depends on the tear type, location, patient age, and overall knee health. Tears in the outer vascular zone have a higher healing potential, while inner avascular zone tears may require surgical intervention. Early diagnosis and appropriate treatment improve outcomes.

Long-term Outcomes

Most patients experience significant improvement in pain and function following appropriate management. Surgical repair generally preserves knee function better than meniscectomy, but some individuals may have residual symptoms or minor limitations in high-impact activities.

Risk of Osteoarthritis

Meniscus damage, particularly when combined with meniscectomy or pre-existing joint degeneration, increases the risk of developing osteoarthritis over time. Preserving meniscal tissue and implementing preventive strategies can help reduce this risk.

References

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