This paper describes 19 cases of lateral meniscal cysts treated arthroscopically using an outside-in technique. In all patients, a horizontal or radial lesion (or both) of the meniscus was present. After the meniscal lesion was arthroscopically removed, the cyst was decompressed both from inside and percutaneously from outside with a motorized instrument introduced through a transmeniscal approach. The follow-up ranged from 2 to 5 years with an average of 3.3 years. On the basis of the evaluation scale developed by Cerullo et al. (1991), the results were rated excellent or good in 17 patients and fair in 2. No patient had cyst recurrence. The computed tomography follow-up examination, done in 10 of the 19 patients after an average of 3 years, showed a good remodeling of the meniscus. One of the two patients with a fair result had hypermobility of the posterior horn of the lateral meniscus due to the resection of the meniscal tissue overlying the popliteus tendon, whereas the other had pain and patellar crepitation owing to a preexisting patellofemoral abnormality.