A 58-year-old woman from rural Maharashtra presents with chronic knee pain and progressive varus deformity. On examination, there is crepitus over the medial knee joint line and restricted flexion. Which is the most common meniscal structure injured in degenerative knee disease?

Explanation

## Meniscal Injury Patterns in Degenerative Knee Disease **Key Point:** The medial meniscus posterior horn is the most common site of degenerative meniscal tears, particularly in patients with progressive osteoarthritis. ### Why the Posterior Horn of the Medial Meniscus? 1. **Anatomical vulnerability:** The posterior horn of the medial meniscus is firmly attached to the joint capsule and has limited mobility. With repetitive loading and age-related degeneration, it becomes prone to horizontal cleavage tears. 2. **Load concentration:** During flexion and weight-bearing, the posterior horn of the medial meniscus bears significant compressive load, accelerating cartilage and meniscal degeneration. 3. **Degenerative pattern:** Unlike traumatic tears (which are often vertical), degenerative tears are typically horizontal cleavage tears affecting the posterior horn. ### Meniscal Injury Patterns: Comparison | Meniscus | Horn | Frequency in Degenerative Disease | Tear Type | Clinical Significance | | --- | --- | --- | --- | --- | | **Medial** | **Posterior** | **Most common (60–70%)** | **Horizontal cleavage** | **Contributes to varus deformity and medial compartment OA** | | Medial | Anterior | 15–20% | Horizontal or radial | Less common in pure degenerative disease | | Lateral | Posterior | 10–15% | Horizontal cleavage | Often associated with lateral compartment OA | | Lateral | Anterior | <5% | Horizontal or radial | Rare in degenerative disease | **High-Yield:** The posterior horn of the medial meniscus is the most frequently affected structure in degenerative knee disease and is a classic NEET PG question. Remember: **medial = posterior** in degenerative disease. **Mnemonic:** **PMHM** = Posterior horn of Medial Meniscus (most common in degenerative disease). **Clinical Pearl:** Patients with posterior horn medial meniscal tears often report: - Pain along the medial joint line (localized to the posterior aspect) - Restricted flexion due to mechanical obstruction - Crepitus and grinding sensations - Progressive varus deformity as the tear widens ### Distinction: Traumatic vs. Degenerative Tears | Feature | Traumatic Tear | Degenerative Tear | | --- | --- | --- | | **Common site** | Lateral meniscus, anterior horn (McMurray's tear) | Medial meniscus, posterior horn | | **Tear pattern** | Vertical (bucket-handle) or radial | Horizontal cleavage | | **Age** | Young, active individuals | Older adults (>50 years) | | **Mechanism** | Acute twisting injury | Chronic loading and degeneration | | **Associated findings** | Acute swelling, locking, giving way | Chronic pain, crepitus, progressive OA | ### Pathophysiology ```mermaid flowchart TD A[Chronic weight-bearing load on medial compartment]:::action --> B[Medial meniscus posterior horn subjected to repeated compression]:::action B --> C[Age-related collagen degeneration and water loss]:::action C --> D[Horizontal cleavage tears develop]:::outcome D --> E[Meniscal extrusion and loss of shock absorption]:::outcome E --> F[Accelerated cartilage degeneration and OA progression]:::urgent F --> G[Varus deformity and functional limitation]:::urgent ```