A tool for measuring functional outcomes after total hip arthroplasty.

To describe a functional milestone scale (FMS) for measuring functional progression following total hip arthroplasty and to demonstrate that this scale meets accepted standards of scale construction.Inter-observer reliability of the scale was determined for 30 patients using a kappa coefficient of concordance (k) for ordinal data, representing 221 pairs of observations. There were 79, 54, 44, and 44 pairs of observations for transfer, walker, crutch, and stair ambulation, respectively.The k coefficient ranged from 0.82 to 0.91. Agreement between therapists was almost perfect according to the criteria of Feinstein.The FMS exhibits substantial inter-observer reliability and moderate to substantial validity. We have demonstrated its clinical applications as well as showing it to be a useful management and research tool.