A 58-year-old woman from rural India presents with chronic knee pain and swelling. On examination, there is a palpable click and occasional locking of the knee. MRI reveals a torn fibrocartilage disc. Which is the most common site of meniscal tear in the knee?

Explanation

## Most Common Site of Meniscal Tear **Key Point:** The posterior horn of the medial meniscus is the most frequently torn region, accounting for approximately 50–60% of all meniscal injuries. ### Why the Posterior Horn of Medial Meniscus? 1. **Biomechanical vulnerability**: The posterior horn is the most mobile and load-bearing segment during flexion and rotation 2. **Firm capsular attachment**: Unlike the lateral meniscus, the medial meniscus is firmly attached to the joint capsule, limiting its ability to escape from between the femur and tibia during rotational movements 3. **Degenerative changes**: The posterior horn is prone to degenerative tears in middle-aged and older patients ### Frequency Distribution of Meniscal Tears | Location | Frequency | Mechanism | |---|---|---| | Posterior horn (medial) | 50–60% | Rotation + flexion, firm capsular attachment | | Posterior horn (lateral) | 20–25% | Less common due to greater mobility | | Anterior horn (medial) | 10–15% | Less load-bearing | | Anterior horn (lateral) | 5–10% | Rare; lateral meniscus more mobile | | Body (both) | <5% | Uncommon | ### Clinical Presentation **High-Yield:** Posterior horn tears present with: - Pain in the posteromedial knee - Clicking or popping sensation - Intermittent locking (if the tear is unstable) - Positive McMurray test (pain with flexion + external rotation) ### Mnemonic **PHMM** — **P**osterior **H**orn **M**edial **M**eniscus (most common tear site). ### Clinical Pearl **Warning:** Do not confuse the most common tear site with the most common meniscal injury overall. While posterior horn medial meniscus tears are most frequent, degenerative tears in older patients may be asymptomatic and discovered incidentally on imaging.