🦵 Lateral Meniscal Tear: Comprehensive Scientific Overview

Introduction

The lateral meniscus is a crucial fibrocartilaginous structure located on the outer aspect of the knee joint. Alongside the medial meniscus, it functions to distribute load, absorb shock, and contribute to joint stability. Though less commonly injured than the medial meniscus, lateral meniscal tears can significantly impair knee function, particularly in athletes and active populations. A deep understanding of the anatomy, mechanisms, classification, and clinical presentation of lateral meniscal tears is essential for physiotherapists to optimize diagnosis, management, and rehabilitation strategies.

Definition

• The lateral meniscus is a C-shaped fibrocartilaginous cartilage that sits between the lateral femoral condyle and lateral tibial plateau.

• It plays a role in load transmission, shock absorption, joint stability, and proprioception.

• A lateral meniscal tear refers to a disruption or damage to the integrity of this cartilage, ranging from minor fraying to complex full-thickness tears that compromise knee biomechanics.

• Due to the more circular shape and greater mobility compared to the medial meniscus, lateral meniscal tears often have distinct clinical characteristics.
  

Cause

• Traumatic injury: Often due to twisting or pivoting motions on a flexed knee, common in sports like soccer, basketball, and skiing. The lateral meniscus is more vulnerable during forced rotation combined with valgus stress.

• Acute injuries often occur in younger, athletic populations during sudden directional changes or collisions.

• Degenerative tears: In older adults, chronic wear and tear or underlying osteoarthritis can weaken the lateral meniscus, causing tears even with minimal trauma.

• Associated ligament injuries: Lateral meniscal tears frequently occur concomitantly with anterior cruciate ligament (ACL) injuries, due to the biomechanical stresses on the lateral compartment during pivoting injuries.
  

Classification

• Tear patterns:

• Longitudinal (vertical) tears: Parallel to circumferential fibers; may progress to bucket-handle tears.

• Radial tears: Extend from the inner free edge toward the periphery, disrupting circumferential fibers and compromising load transmission.

• Horizontal cleavage tears: Split the meniscus into superior and inferior leaflets, often degenerative.

• Complex tears: Combination of patterns with irregular shapes, often unstable.

• Flap tears: Displaced tears causing mechanical symptoms.

• Location-based classification:

• Red zone: Outer third with good blood supply; better healing potential.

• White zone: Inner two-thirds with poor vascularity; limited healing capacity.

• Severity grading:

• Grade I: Minor fraying or intrasubstance changes.

• Grade II: Partial thickness tear without surface disruption.

• Grade III: Full-thickness tear extending through the meniscus.

• Associated injuries: Important to note concomitant ligament injuries (especially ACL) which influence treatment decisions.
  

Signs and Symptoms

• Pain: Usually localized to the lateral aspect of the knee, exacerbated by activities that load the joint such as squatting, twisting, or pivoting.

• Swelling: May develop acutely or gradually within 24-48 hours post-injury.

• Mechanical symptoms: Locking, catching, or clicking sensations due to displaced meniscal fragments or unstable tears.

• Joint line tenderness: Palpation along the lateral joint line typically reproduces pain.

• Reduced range of motion: Particularly with knee flexion or extension due to pain or mechanical blockage.

• Instability or giving way: Less common than with ligament injuries but can occur with large tears affecting joint congruity.

• Positive special tests: McMurray’s test and Thessaly test often reproduce symptoms and assist clinical diagnosis.
  

Conclusion

Lateral meniscal tears represent a significant pathology that can impair knee function and quality of life, especially in active individuals. Prompt and accurate diagnosis, aided by clinical evaluation and imaging, is critical. Treatment ranges from conservative management with physiotherapy to surgical intervention depending on tear type, location, patient activity level, and associated injuries. A thorough understanding of lateral meniscal tear pathology enables physiotherapists to tailor rehabilitation programs that restore function, alleviate symptoms, and reduce long-term joint degeneration.