Meniscal rupture

A meniscal rupture is one of the most common knee injuries, particularly affecting athletes and individuals engaged in activities that require twisting or pivoting movements. The menisci play a critical role in shock absorption, load distribution, and joint stability within the knee. Understanding the anatomy, mechanism, and classification of meniscal tears is essential for accurate diagnosis and effective management.

Anatomy and Function of the Meniscus

Structure of the Menisci

The menisci are two crescent-shaped fibrocartilaginous structures situated between the femoral condyles and the tibial plateau. Each knee joint contains a medial and a lateral meniscus, both composed primarily of type I collagen fibers arranged circumferentially to resist compressive and shear forces. The outer region of the meniscus is thicker and more vascular, while the inner region is thinner and avascular.

Types: Medial and Lateral Meniscus

The medial meniscus is C-shaped and more firmly attached to the tibial plateau, making it more susceptible to injury. The lateral meniscus is nearly circular, more mobile, and less frequently injured due to its loose attachment and greater capacity for movement during joint motion.

Blood Supply and Innervation

The menisci receive blood supply from the perimeniscal capillary plexus derived from the genicular arteries. Vascularization is limited to the outer third (red-red zone), while the inner two-thirds (red-white and white-white zones) are relatively avascular and rely on synovial diffusion for nutrition. Sensory innervation is present mainly in the peripheral region, contributing to proprioception and pain sensation following injury.

Biomechanical Role in the Knee Joint

• Distributes load across the tibiofemoral joint to reduce stress on articular cartilage.
• Provides shock absorption during weight-bearing and impact activities.
• Enhances joint stability by deepening the articular surface of the tibia.
• Facilitates lubrication and nutrition of the knee joint through synovial fluid distribution.

Definition and Classification of Meniscal Rupture

Definition

A meniscal rupture, or meniscal tear, refers to a partial or complete disruption of the fibrocartilaginous tissue of the meniscus. The injury may result from trauma, degeneration, or repetitive stress and can vary in severity and pattern depending on the mechanism involved.

Types of Tears

• Longitudinal tear: A vertical tear that runs parallel to the circumferential fibers, often progressing into a bucket-handle tear.
• Radial tear: Extends from the inner free edge toward the periphery, disrupting circumferential fiber continuity.
• Horizontal tear: Splits the meniscus into upper and lower portions, commonly associated with degeneration.
• Bucket-handle tear: A displaced longitudinal tear where a fragment folds inward, causing joint locking.
• Complex tear: A combination of different tear patterns, often seen in chronic or degenerative conditions.

Zones of Involvement (Red-Red, Red-White, White-White)

Zone	Vascular Supply	Healing Potential
Red-Red Zone	Well vascularized	High healing potential
Red-White Zone	Partially vascularized	Moderate healing potential
White-White Zone	Avascular	Poor healing potential

Etiology and Risk Factors

Traumatic Causes

Traumatic meniscal ruptures are commonly associated with sudden twisting or pivoting movements of the knee, particularly when the foot is planted on the ground. These injuries are frequent in sports such as football, basketball, and skiing. Direct trauma to the knee, such as a collision or fall, may also result in meniscal damage.

Degenerative Causes

Degenerative tears occur gradually as the meniscal tissue weakens with age or repetitive mechanical stress. These are more common in older adults and individuals with osteoarthritic changes in the knee joint. The meniscus becomes less elastic and more prone to tearing even with minimal stress.

Predisposing Factors

• Age: The risk of degenerative meniscal tears increases after the age of 40 due to reduced vascularity and tissue elasticity.
• Activity level: High-impact sports and occupations requiring kneeling or squatting increase the likelihood of meniscal injury.
• Previous knee injuries: Ligamentous injuries, particularly anterior cruciate ligament (ACL) tears, predispose the knee to secondary meniscal damage.
• Joint instability or malalignment: Abnormal knee biomechanics and varus or valgus deformities place uneven stress on the menisci.

Pathophysiology

Mechanism of Injury

The meniscus can tear when subjected to excessive shear or compressive forces, especially during combined flexion and rotation of the knee. The medial meniscus is more frequently injured because of its firm attachment to the tibial plateau and joint capsule, whereas the lateral meniscus is more mobile and relatively protected.

Biomechanical Disruption in Knee Stability

A meniscal rupture compromises the ability of the meniscus to distribute joint loads effectively. The resulting uneven pressure increases stress on the articular cartilage, accelerating degenerative changes and predisposing the joint to osteoarthritis. Additionally, the loss of the meniscus’s wedge effect can lead to instability during movement.

Inflammatory Response and Degeneration

Following a meniscal tear, an inflammatory response occurs with the release of cytokines and enzymes that contribute to pain, swelling, and cartilage degradation. Over time, chronic inflammation and altered joint mechanics can lead to progressive joint degeneration, reduced mobility, and persistent discomfort.

Clinical Presentation

Symptoms

• Pain: Localized pain along the joint line, often exacerbated by twisting, squatting, or climbing stairs.
• Swelling: Mild to moderate effusion may appear within a few hours after injury, indicating intra-articular irritation.
• Locking or clicking sensation: A torn fragment may interfere with normal joint movement, causing mechanical locking or audible clicks.
• Restricted range of motion: Flexion and extension of the knee may be limited due to pain or obstruction by the displaced tear.

Physical Examination Findings

• Joint line tenderness: Palpation along the medial or lateral joint line reveals localized pain corresponding to the site of the tear.
• McMurray test: A palpable or audible click during knee flexion and rotation suggests a meniscal tear.
• Apley grind test: Pain produced during compression and rotation of the flexed knee indicates possible meniscal damage.
• Thessaly test: Pain or locking while the patient twists on a slightly flexed knee is a strong indicator of meniscal injury.

Diagnostic Evaluation

Imaging Studies

• X-ray findings: While X-rays do not show soft tissue injuries, they help exclude associated fractures or degenerative joint disease.
• MRI features: MRI is the gold standard for non-invasive diagnosis, revealing the tear pattern, location, and associated ligamentous injuries.
• Ultrasound assessment: Useful in detecting large tears or displaced fragments in superficial regions of the knee joint.

Arthroscopy as a Diagnostic Tool

Diagnostic arthroscopy allows direct visualization of the meniscus, enabling accurate identification of tear type, location, and severity. It is both diagnostic and therapeutic, as repair or debridement can be performed in the same procedure.

Differential Diagnosis

• Ligamentous injuries, particularly anterior cruciate ligament (ACL) tears
• Patellofemoral pain syndrome
• Osteoarthritis of the knee
• Plica syndrome or synovial fold irritation
• Loose bodies within the joint space

Classification Systems

Based on Morphology

Meniscal ruptures are classified according to the pattern and orientation of the tear within the fibrocartilage. Morphological classification assists clinicians in determining the appropriate treatment strategy and predicting healing potential.

• Longitudinal tear: Vertical split following the circumferential fibers, often seen in young athletes.
• Radial tear: Extends from the inner margin toward the periphery, disrupting hoop stress and stability.
• Horizontal tear: Separates the meniscus into superior and inferior portions, frequently degenerative in origin.
• Bucket-handle tear: A displaced longitudinal tear that may cause locking or catching of the knee joint.
• Complex tear: Combination of multiple tear patterns, typically associated with chronic degeneration.

Based on Vascular Zone Involvement

This classification categorizes tears according to their location relative to the meniscus’s vascular supply, influencing the healing potential and management plan.

Zone	Description	Healing Potential
Red-Red Zone	Peripheral, well-vascularized region	Excellent potential for healing with repair
Red-White Zone	Intermediate region with partial vascularity	Moderate healing potential
White-White Zone	Inner avascular region	Poor healing; often requires partial meniscectomy

Based on Chronicity (Acute vs. Chronic)

• Acute tears: Result from sudden trauma, typically in younger individuals with healthy cartilage.
• Chronic tears: Develop gradually due to degenerative processes and repetitive stress, often in older adults.

Management and Treatment

Conservative Treatment

Initial management is often non-surgical, particularly for small or stable tears located in vascular zones. Conservative care aims to reduce inflammation, restore mobility, and strengthen surrounding musculature.

• Rest, Ice, Compression, Elevation (RICE): Reduces pain and swelling during the acute phase.
• Physiotherapy: Includes range-of-motion exercises, quadriceps strengthening, and proprioceptive training.
• Bracing and activity modification: Knee braces and avoidance of twisting or pivoting movements aid healing.
• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to manage pain and inflammation.

Surgical Management

When conservative therapy fails or when the tear affects function, surgical intervention is indicated. The type of procedure depends on tear location, pattern, and vascularity.

• Meniscectomy: Partial removal of the damaged meniscal portion to alleviate symptoms while preserving as much tissue as possible.
• Meniscal repair: Suturing of the tear, typically in the red-red or red-white zones, to preserve meniscal integrity and function.
• Meniscal transplantation: Performed in younger patients with prior total meniscectomy and persistent joint pain or dysfunction.

Postoperative Care and Rehabilitation

Rehabilitation following surgery focuses on gradual restoration of knee motion, muscle strengthening, and progressive weight-bearing. Physiotherapy protocols are individualized, emphasizing joint stability and prevention of re-injury.

Complications

Post-Traumatic Osteoarthritis

One of the most significant long-term complications of meniscal rupture or meniscectomy is the development of osteoarthritis. Loss of meniscal integrity disrupts normal load distribution, leading to increased contact stress on the articular cartilage and subsequent degeneration of the joint surface.

Recurrent Tears

Recurrent meniscal tears may occur after incomplete healing or following surgical repair, particularly if patients return to high-impact activities prematurely. Repeated injury can result in progressive loss of meniscal tissue and further compromise joint function.

Joint Instability

A meniscal tear may alter the normal biomechanics of the knee, leading to rotational instability or an increased risk of associated ligament injuries. Chronic instability can exacerbate wear on cartilage and accelerate degenerative changes.

Persistent Pain and Stiffness

Residual pain, stiffness, and swelling may persist after injury or surgical intervention. These symptoms are often due to incomplete rehabilitation, scar tissue formation, or concurrent chondral damage within the joint.

Prognosis and Outcomes

Healing Potential by Zone

The prognosis of a meniscal rupture depends largely on the vascularity of the affected zone. Tears in the outer vascular regions (red-red and red-white zones) have a better chance of healing spontaneously or after repair. In contrast, tears within the avascular white-white zone rarely heal without surgical intervention.

Factors Affecting Recovery

• Age: Younger individuals exhibit better healing capacity due to increased tissue vascularity and cellular activity.
• Tear type and location: Longitudinal tears near the periphery heal more effectively than complex or degenerative tears in the inner region.
• Associated injuries: Concurrent ligament injuries, such as ACL tears, may delay recovery and require combined treatment.
• Postoperative compliance: Adherence to physiotherapy and rehabilitation significantly influences long-term outcomes.

Long-Term Functional Outcomes

With appropriate management, most patients regain satisfactory knee function and return to normal activities. Early diagnosis and preservation of meniscal tissue improve long-term joint stability and reduce the likelihood of degenerative changes. However, untreated or inadequately managed tears may lead to chronic pain, reduced mobility, and early onset of osteoarthritis.

Prevention and Patient Education

Preventive Strategies

Prevention of meniscal rupture focuses on minimizing excessive knee stress and maintaining optimal joint health. Proper training, muscle conditioning, and protective techniques are key to reducing the risk of injury, especially among athletes and physically active individuals.

• Warm-up and stretching: Engaging in adequate warm-up routines before sports or exercise enhances muscle flexibility and joint mobility.
• Use of proper technique: Correct landing and pivoting mechanics reduce torsional stress on the knee joint.
• Appropriate footwear: Wearing supportive and sport-specific shoes helps maintain alignment and stability during movement.
• Strengthening programs: Regular exercises targeting quadriceps, hamstrings, and calf muscles improve joint stability and balance.

Strengthening and Flexibility Programs

Structured exercise regimens play a major role in protecting the menisci and surrounding structures. Strengthening programs should include both isotonic and isometric exercises to build muscle endurance without overloading the knee. Flexibility routines, such as stretching and yoga, help maintain optimal range of motion and prevent soft tissue tightness that could predispose to injury.

Patient Counseling and Lifestyle Modifications

Patient education is essential in preventing re-injury and promoting long-term joint health. Individuals recovering from meniscal tears should be advised to avoid deep squatting, twisting, and high-impact sports until full rehabilitation is achieved. Maintaining a healthy body weight reduces stress on the knees and lowers the risk of recurrent tears or degenerative joint disease.

References

1. Standring S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. London: Elsevier; 2020.
2. Reicher MA, Hartzman S, Duckwiler GR, Bassett LW, Anderson LJ, Gold RH. Meniscal Tears: Pathologic Correlation with MR Imaging. Radiology. 1986;160(2):343–347.
3. Verdonk PC, Almqvist KF, Huysse W, Verdonk R. Meniscal Allograft Transplantation: Long-term Clinical Results. Knee Surg Sports Traumatol Arthrosc. 2006;14(8):694–706.
4. Fox AJ, Wanivenhaus F, Burge AJ, Warren RF, Rodeo SA. The Human Meniscus: A Review of Anatomy, Function, Injury, and Advances in Treatment. Clin Anat. 2015;28(2):269–287.
5. Makris EA, Hadidi P, Athanasiou KA. The Knee Meniscus: Structure–Function, Pathophysiology, Current Repair Techniques, and Prospects for Regeneration. Biomaterials. 2011;32(30):7411–7431.
6. Stein T, Mehling AP, Welsch F, von Eisenhart-Rothe R, Jäger A. Long-term Outcome after Arthroscopic Meniscal Repair versus Arthroscopic Partial Meniscectomy for Traumatic Meniscal Tears. Am J Sports Med. 2010;38(8):1542–1548.
7. Brindle T, Nyland J, Johnson DL. The Meniscus: Review of Basic Principles with Application to Surgery and Rehabilitation. J Athl Train. 2001;36(2):160–169.
8. Neumann DA. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 4th ed. St. Louis: Elsevier; 2020.