The hypermobile lateral meniscus (HLM) is one of the causes of lateral knee pain and a locking sensation. In children the cause tends to be due to congenital absence of posterior capsular attachments, whilst in adults it is more likely traumatic.
There is a bimodal age distribution pattern of patients with hypermobile lateral meniscus. In children, the onset is in older preteens and teenagers. The majority of pediatric patients cannot recall a traumatic event and most cases are bilateral.
In adults, on the other hand, a remembered history of trauma is usually present.
The main symptoms are lateral knee pain and intermittent locking and catching of the joint. On physical examination, a provocative maneuver known as the Figure-4 test which places the affected knee in flexion, varus and external rotation may reproduce locking in patients with a hypermobile lateral meniscus 3.
In pediatric population, it is thought to be secondary to the congenital absence of the meniscotibial ligament or meniscocapsular attachments.
In adults, the disruption of the popliteomeniscal fascicles is usually secondary to trauma which may lead to hypermobility of the lateral meniscus.
In cases of hypermobile lateral meniscus, the posterior portion of the lateral meniscus shows paradoxical excessive forward translation with knee flexion and posterior translation with knee extension 4.
High incidence of abnormal posterosuperior and anteroinferior popliteomeniscal fascicles is present in patients with recurrent lateral meniscal subluxation. Posterosuperior fascicle abnormality can be seen in asymptomatic patients, but an abnormal anteroinferior popliteomeniscal fascicle is essential to allow lateral meniscal subluxation, and is consistently seen in hypermobile lateral meniscus.
Treatment and prognosis
Meniscal preservation and stabilisation by fixation of the meniscus to the posterior capsule, usually via an arthroscopic approach is the treatment of choice 3,5.
- 1. The Diagnosis and Treatment of Hypermobile Lateral Meniscus. (1992) Japanese Journal of Rheumatism and Joint Surgery. 11 (2): 143. doi:10.11551/jsjd1982.11.143
- 2. Peduto AJ, Nguyen A, Trudell DJ, Resnick DL. Popliteomeniscal fascicles: anatomic considerations using MR arthrography in cadavers. (2008) AJR. American journal of roentgenology. 190 (2): 442-8. doi:10.2214/AJR.07.2643 - Pubmed
- 3. LaPrade RF, Konowalchuk BK. Popliteomeniscal fascicle tears causing symptomatic lateral compartment knee pain: diagnosis by the figure-4 test and treatment by open repair. (2005) The American journal of sports medicine. 33 (8): 1231-6. doi:10.1177/0363546504274144 - Pubmed
- 4. Garofalo R, Kombot C, Borens O, Djahangiri A, Mouhsine E. Locking knee caused by subluxation of the posterior horn of the lateral meniscus. (2005) Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 13 (7): 569-71. doi:10.1007/s00167-004-0581-x - Pubmed
- 5. Van Steyn MO, Mariscalco MW, Pedroza AD, Smerek J, Kaeding CC, Flanigan DC. The hypermobile lateral meniscus: a retrospective review of presentation, imaging, treatment, and results. (2016) Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 24 (5): 1555-9. doi:10.1007/s00167-014-3497-0 - Pubmed