A novel methodological approach for measuring symptomatic change following total joint arthroplasty.

The OHS/OKS are PROMs for assessing symptomatic pain and function following TJA. However, actual change in pre-operative/post-operative scores cannot distinguish patients of varying baseline symptom severity. The percentage of potential change (PoPC) is a simple method that accounts for this, expressing the actual change attained, as a percentage of the potential change possible. Measures are described using OHS/OKS at baseline and 6-months (1784 - TKA, 1523 - THA) from the Elective Orthopaedic Centre. Each method identified different proportions of patients as satisfied and importantly, the measures identified different patients. PoPC overcomes floor and ceiling effects and standardises measures to an easy to interpret -100 to +100 scale. In addition to actual change, we recommend using PoPC to assess the overall outcome of patients.