Of 198 patients with popliteal cyst who were seen during a ten-year period, eighty-two underwent eighty-three operations—total excision of the cyst. The patient had usually complained of a mass and of aching pain in the region of the knee. More than a fifth of the eighty-two patients were less than sixteen years old. Although other disease of the knee joint, which was associated with the cyst in 45 per cent of the 198 patients, apparently did not predispose to recurrence of the cyst after operation, it did seem to increase the chance that the patient would continue to complain of trouble with the joint after operation.

At operation, forty-six of the eighty-three cysts seemed to arise from bursae, twenty-six from herniae, and eleven from indeterminate sites. Communication of the cyst with the joint was evident in fifty-four, twenty-seven of these being hernial in origin, twenty-two being bursal, and five being indeterminate. Failure to close the capsule when the cyst communicated with the knee did not seem to predispose to recurrence.

Pathologically the cysts were classified as fibrous, synovial, inflammatory, and, in a few instances, transitional. No particular type or lining characterized either the bursal or the hernial cyst.

Only five patients had recurrence of the cyst, but twenty-seven had persistence of some degree of symptoms, twenty-one of whom had associated disease of the knee joint.

The name popliteal cyst seems preferable to the names used heretofore, regardless of where the cyst arises, since all these lesions apparently behave alike clinically and pathologically, have the same indications for treatment, and terminate similarly.