Meniscal cyst

The incidence of meniscal cysts varies in report form 1 tot 20 percent and they are much more common laterally. They usually present in young adult males and are often associated with horizontal meniscal tears. The lateral meniscal cyst also can be associated with a peroneal nerve compression syndrome.

Anatomy

The lateral meniscus is C-shaped and has attachments at front and backside to the intercondylar eminence. There are peripheral attachments to the lateral capsule, but no attachments to the lateral ligament of the knee. during flexion of the knee the meniscus moves from the front to the backside of the tibial plateau. A discoid meniscus is found at the lateral side 50 times more then at the medial side, and this form prone to injury.

Diagnosis
With inspection or palpation local tenderness and swelling can be found at the joint line.
The diagnosis can be evaluated by ultrasound, or magnetic resonance imaging when necessary, as in the latter also an internal derangement of the meniscus can be distinguised.

Treatment
Conservative treatment is recommended in the patient with few symptoms. Should the cyst become significantly symptomatic, it is necessary to treat the meniscal pathology by resecting the meniscus arthroscopically back to normal meniscus residue. Aspirating and injecting the cyst or local cystic excision is a less favorable way of resolving the problem, meaning that this gives no possibility to inspect the condition of de meniscus.
In the rehabilitation program emphasis must given to training of the adductors of the hip with exercises in closed chain.

References
Maffuli, N. Petricciuolo F. Pintore E. Lateral meniscal cyst: arthroscopic management. Med Sci Sports Exerc 23 (7) 1991, 779-782.
Lantz, B. Singer KM. Meniscal cysts. Clinics in sports medicine 9 (3) 1990, 707-725.