The meniscus is a crescent-shaped cartilage structure that plays a crucial role within the knee joint, acting as a shock absorber.

Meniscus injury disorder, often colloquially referred to as a torn meniscus, represents one of the most common orthopedic knee problems and can significantly impair mobility and quality of life.

Anatomy and Function of the Meniscus

Within each knee joint, two menisci—the medial (inner) and lateral (outer) serve to distribute weight and reduce friction during knee movement. Composed of tough, rubbery cartilage, these structures absorb impact and contribute to joint stability by deepening the articulation of the knee bones. Their unique composition and limited blood supply, especially in the central zones, influence their capacity for healing following injury.

Etiology: How Meniscus Injuries Occur

Meniscus injuries arise primarily from two mechanisms: acute trauma and degenerative wear. Acute meniscus tears typically result from sudden twisting or pivoting movements when the foot is firmly planted, often seen in athletes engaging in sports like basketball, soccer, and tennis.

Such maneuvers exert rotational forces exceeding the meniscal tensile strength, leading to tears. Traumatic injuries can also be accompanied by other knee ligament damages, such as anterior cruciate ligament tears.

Conversely, degenerative meniscus injuries pertain to the gradual deterioration of cartilage over time, usually affecting older adults or individuals with osteoarthritis. This degeneration weakens the meniscal tissue, making it susceptible to tears even during minimal stress or routine activities like rising from a chair or stepping awkwardly.

Types and Patterns of Meniscus Tears

Meniscus tears manifest in distinct patterns, each with specific implications for treatment and prognosis:

Vertical Longitudinal Tears: These run lengthwise and are often located in the vascularized outer meniscal zone, permitting potential healing.

Bucket-Handle Tears: A subtype of longitudinal tear where a fragment detaches and flips into the joint, causing mechanical symptoms like locking.

Radial Tears: These extend perpendicular from the inner rim outward and usually disrupt meniscal integrity, challenging repair potential due to limited blood supply.

Horizontal (Intrasubstance) Tears: Common in degenerative cases, characterized by cleavage between meniscal layers.

Complex Tears: Combinations of the above patterns, frequently requiring surgical intervention.

Clinical Presentation: Recognizing Symptoms

Patients with meniscus injuries typically present with knee pain localized to the inner or outer joint line, often exacerbated by twisting or squatting movements. Swelling and stiffness may develop within hours or days following the injury, limiting knee flexion or full extension.

Mechanical symptoms such as catching, locking, or a sensation of knee instability often accompany displaced tears, notably bucket-handle types. An audible or palpable "pop" at the time of injury is a hallmark sign. In degenerative tears, symptoms may be insidious, with intermittent discomfort and gradual functional decline.

Diagnostic Evaluation

Thorough clinical assessment includes physical examination maneuvers such as McMurray's test and joint line palpation to localize pain and evaluate meniscal integrity. Imaging plays a pivotal role in confirming diagnosis and planning treatment.

Magnetic resonance imaging (MRI) is the gold standard non-invasive modality, offering detailed visualization of meniscal morphology and associated intra-articular pathology. Radiographs, although primarily excluding fractures or advanced osteoarthritis, can supplement the diagnostic workup.

Treatment Modalities: From Conservative to Surgical

Management strategies depend on tear type, patient age, activity level, and symptom severity. Conservative treatment for minor or stable tears includes rest, ice application, compression, elevation (RICE), and nonsteroidal anti-inflammatory drugs (NSAIDs) to alleviate pain and swelling. Physical therapy focuses on strength and flexibility to support joint function.

Surgical intervention is considered for persistent symptoms, mechanical blockage, or unstable tears. Arthroscopic procedures allow minimally invasive partial meniscectomy (removal of damaged cartilage) or meniscal repair by suturing in vascularized zones to promote healing.

Criteria for repair include tear location, chronicity, and tissue quality. Emerging tissue engineering and regenerative approaches hold promise for enhanced recovery in meniscal pathology.

"In a young person with a significant injury, a sporting injury, maybe they have a torn ACL as well, a meniscus tear can be a significant factor in their final outcome a few years down the road," says Dr. John-Paul Rue, orthopedic surgeon.

Meniscus injury disorder epitomizes a complex spectrum of knee cartilage damage ranging from acute traumatic tears to degenerative lesions. The menisci's essential biomechanical roles underscore the significance of timely and precise diagnosis coupled with tailored therapeutic approaches.

Through a combination of conservative management and advanced surgical techniques, functional restoration and mitigation of long-term joint degeneration are achievable, preserving mobility and quality of life.