Meniscal Lesions: Diagnosis and Treatment

Robert S. P. Fan, MD, Richard K. N. Ryu, MD

Disclosures
In This Article

Meniscal Cysts

Parameniscal cysts occur relatively infrequently. They are usually associated with horizontal cleavage tears. However, isolated cysts without meniscal pathology have also been reported. Although the incidence of cysts is usually higher on the lateral side, some studies report an equal incidence. [53,54]

Meniscal cysts were first described by Ebner[55] in 1904. Their incidence ranges from 1% to 22%.[56,57,58] Several theories have been proposed regarding cyst etiology, including traumatic origin, as well as purely degenerative origin. Barrie[59] performed histopathologic studies that provided great insight into cyst etiology. He postulated that meniscal cyst formation originated by influx of synovial fluid through microscopic and gross tears in the substance of the meniscus. In 112 cysts, he demonstrated a meniscal tear with a horizontal component, as well as a tract that provided an exchange of fluid between the joint and the cyst. Meniscal cysts typically are multilocular and are lined with synovial endothelial tissue. Meniscal cysts have been reported, however, in the absence of meniscal pathology, a factor that may alter the surgical treatment of the meniscal cyst.

In the absence of a meniscal tear, it has been proposed that a parameniscal cyst may develop from a compression injury to the periphery of a meniscus that has central degeneration.[60] A meniscal cyst may then develop more peripherally, leaving the body of the meniscus abnormal, but not torn. In addition, cyst-like structures may develop that are histologically different from those associated with meniscal tears.[61]

A meniscal cyst may present with signs and symptoms consistent with typical meniscal pathology. Intermittent swelling at the joint line is variable, while pain over the area is quite common. Pisani[62] described that a lesion that decreases in size with knee flexion and increases with extension is consistent with a meniscal cyst.

The MRI is valuable for confirming the presence of a suspected meniscal cyst and identifying any concurrent meniscal tear (Figure 16).

MRI finding of complex serpiginous tract (arrow) associated with lateral meniscal tear, with cyst presenting adjacent to the patellar tendon. (Reprinted with permission.)

Ryu RKN, Ting AJ. Arthroscopic treatment of meniscal cysts. Arthroscopy. 1993:591-595, Figure 3.

The management of a meniscal cyst consists of diagnostic arthroscopy to determine the presence of a meniscal tear. In the presence of a meniscal tear, partial meniscectomy followed by arthroscopic cyst decompression is the treatment of choice. If a tear is not confirmed at the time of arthroscopy, then open-cyst decompression with peripheral meniscal repair becomes the logical treatment option, thereby leaving the body of the meniscus unviolated. In the presence of a small meniscal tear, an arthroscopic limited partial meniscectomy may be performed, and if no tract is identified, then conversion to an open cystectomy may similarly preserve the peripheral meniscal body.[52,53,63]

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