This patient-reported outcome-based performance measure uses the same measure specifications as the NQF-endorsed (NQF # 3559) hospital-level risk-standardized improvement rate (RSIR) following elective primary THA/TKA with the following exception: this measure attributes the outcome to a clinician or clinician group. Specifically, this measure will estimate a clinician-level and/or a clinician group-level RSIR following elective primary THA/TKA for Medicare fee-for-service (FFS) patients 65 years of age and older.