Pigmented villonodular synovitis (PVNS) is a proliferative disorder that may lead to joint destruction and activity limitation. We conducted a retrospective study to determine the long-term results of localized PVNS (LPVNS) treated with arthroscopic excision, specifically with respect to postoperative activity level and symptom resolution. We reviewed the cases of 11 patients who had been treated with arthroscopic excision and partial synovectomy of LPVNS and were observed for a mean of 112 months. Preoperative and postoperative Ogilvie-Harris scores, Tegner activity level scores, and UCLA activity level scores were calculated to determine disease-specific and general functional outcomes, respectively. We noted recurrence of posteromedial lesions in 2 cases, moderate resolution of preoperative symptoms in most cases, and the development of secondary osteoarthritis requiring surgical intervention in 2 cases. Arthroscopic excision of LPVNS can improve symptoms with a return to preoperative activity levels, but patients may develop secondary osteoarthritis after treatment, as noted in long-term follow-up.