- Meniscal cyst
-
A meniscal cyst is a well-defined cystic lesion located along the peripheral margin of the meniscus, a part of the knee, nearly always associated with horizontal meniscal tears.
Contents
Signs and symptoms
Pain and swelling or focal mass at the level of the joint. The pain may be related to a meniscal tear or distension of the knee capsule or both. The mass varies in consistency from soft/fluctuant to hard. Size is variable, and meniscal cysts are known to change in size with knee flexion/extension.
Cause
Various etiologies have been proposed, including trauma, hemorrhage, chronic infection, and mucoid degeneration. The most widely accepted theory describes meniscal cysts resulting from extrusion of synovial fluid through a peripherally extended horizontal meniscal tear, accumulating outside the joint capsule. They arise more commonly from the lateral joint margin, and occur most often in 20 to 40 year old males.
Diagnosis
Magnetic resonance imaging is the modality of choice for diagnosis of meniscal cysts. In their most subtle form, meniscal cysts present as focal areas of high signal intensity within a swollen meniscus. It is not uncommon for radiologists to miss this type of meniscal cyst because the signal intensity is not quite as great as fluid on T2 weighted sequences.2 When this fluid is extruded into the adjacent soft tissues, the swollen meniscus subsequently assumes a more normal shape, and the extruded fluid demonstrates a higher T2 signal typical of parameniscal cysts.
Medial meniscus horizontal tear extending into a meniscal cyst.
Sagittal T2 images of a medial meniscus horizontal tear extending into a meniscal cyst.
Large medial meniscus cyst.
Treatment
Treatment of meniscal cysts consists of a combination of cyst decompression (intraarticular decompression versus open cystectomy) and arthroscopic repair of any meniscal abnormalities. Success rates are significantly higher when both the cyst and meniscal tear are treated compared to treating only one disease process.
See also
References
- Meniscal Cysts by Rob Gutierrez, M.D.
- Campbell, SE, Sanders, TG, Morrison, WB. MR imaging of meniscal cysts: Incidence, location, and clinical significance. AJR 2001;177:409-413.
- Helms, CA. The meniscus: Recent advances in MR imaging of the knee. AJR 2002;179(5):1115-1112.
There is at least one other form of meniscal cyst. It is multi-loculated with cysts 1-2 mms in diameter and occurs mainly in the substance of the lateral meniscus close to the menisco-capsular boundary. The cysts seem to increase in number, spreading very slowly into the adjoning parts of the meniscus. When the cystic mass distends the meniscus sufficiently a split in the meniscus may develop. It is not normally visible to the arthroscope.
Signs and Symptoms
It presents as a swelling on the joint line sometimes accompanied by an ache.
Causes
It is a multicentric mucoid degeneration of unknown origin.
Diagnosis
A presumptive diagnosis can be made if the swelling becomes less prominent when the knee is bent. It can be visualised on MRI.
Treatment
Treatment is by excising the abnormal tissues by open surgery, approaching through an incision directly over the swelling. Arthroscopic excision is usually not possible.
References
Flynn M & Kelly JP. JBJS Br. 58(1): 88-9.
Also JBJS Br. 58(4): 367
Categories:
Wikimedia Foundation. 2010.
