A retrospective study was performed on 122 patients with 124 lateral meniscal cysts, selected from a series of 8100 knee arthroscopies (1.5 per cent). Eight of the patients were lost for follow up, 11 patients had chronic anterior cruciate ligament deficiency or previous medial meniscectomy. Therefore 105 of 124 patients were included in this study. Average follow-up was 5 years (range of 1 to 12.5 years).
Mean age was 33 years (range of 12 to 69 years). All patients had pain over the joint line with a palpable mass. All were noted to have a meniscal tear at the time of surgery and 60 (57 per cent) had a horizontal cleavage component. They were all arthroscopically treated.
Meniscal tears were treated by arthroscopic partial meniscectomy in 104 cases and meniscal repair in one case. Cysts were treated by intra-articular debridement in 91 cases and open cystremoval in 14 cases. Eleven cysts recurred and a second arthroscopy was required. The clinical results, including cysts recurrence, were excellent or good in 87 per cent of cases. Osteoarthritis following treatment of these meniscal cysts occurred in 9 per cent of cases.
When there is a cyst and no other intra-articular damage, the prognosis was excellent at 5 year follow-up. For lateral meniscal cysts; arthroscopic partial meniscectomy with intra-articular debridement yields predictable results.