To quantify the magnitude of change seen with pain, function, and quality of life outcomes 6 months after total hip and knee arthroplasties (THA, TKA) within a community based cohort of a regional health district. An inception cohort of 504 patients who received primary THA (228) or TKA (276) was prospectively followed. All patients resided in the community and were assessed within one month prior to surgery and 6 months postoperatively. Health related quality of life measures were evaluated with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and the Medical Outcome Survey Short Form SF-36. Perioperative factors were extracted from medical charts. Health services utilization data were collected from regional health databases. Over 75% of patients reported improvement in joint-specific pain and function, regardless of the type of joint replaced. Other health dimensions such as social function, bodily pain, physical function, vitality, and general health showed significant improvement after surgery. Those psychosocial dimensions with modest changes had baseline values comparable to age and sex adjusted normal values; whereas, bodily pain and physical function, which had large changes, had values lower than the normal values. Ninety-one percent of patients receiving THA were satisfied with their surgery, whereas 77% were satisfied with their TKA. The average length of stay was 7 days and the in-hospital complication rate was 0.34 per patient. Large improvements were reported for pain and function after joint arthroplasties, while small to moderate changes were seen in other areas related to quality of life. Patients with hip arthroplasties showed greater improvement in pain and function and were more satisfied with their outcomes than patients with knee arthroplasties. Although pain and function show large improvements, bodily pain and physical function were less than the values reported in the general population.