Cysts of the lateral meniscus: arthroscopy versus arthroscopy plus open cystectomy.

A retrospective analysis was performed on 32 knees in 31 patients with the diagnosis of cyst of the lateral meniscus. Average follow-up was 41 months, with a range of 16-72 months. Surgical and histological examination demonstrated pathology varying from large meniscal tears with minimal cyst formation to large cysts with no demonstrable meniscal tear. Two theories of etiology emerged: (a) The tear begins in the meniscus and spreads through the periphery. (b) The lesion begins as a compression injury to the vascular periphery and spreads centrally, producing a meniscus tear, or peripherally, producing a cyst, or both. In our series, 20 patients managed by arthroscopic partial meniscectomy and open cystectomy had 80% excellent-good results versus 50% excellent-good results in 12 patients treated with arthroscopy and partial meniscectomy without extraarticular cystectomy. We recommend the following treatment: arthroscopy with a diligent search for a lateral meniscal tear, especially peripherally. If none is found, proceed to extraarticular cystectomy. If a tear is found, remove all unstable meniscal fragments, leaving a rim, if possible, especially adjacent to the popliteus recess, and then proceed to open cystectomy.