BACKGROUND:We aimed to compare the performance of EQ-5D-3 L and howRu, which are short generic patient-reported outcome measures (PROMs), in assessing the outcome of hip and knee replacements, using the Oxford Hip Score (OHS) and the Oxford Knee Scores (OKS) for comparison. METHODS:Outcome was assessed as the difference between pre-surgery and 6-month post-surgery scores. We used a large sample from the NHS PROMs database, which used EQ-5D-3 L, and a small cohort of patients having the same operations collected by MyClinicalOutcomes (MCO), which used howRu. Both cohorts completed the OHS (hips) or the OKS (knees). RESULTS:The change (outcome) between pre-op and post-op scores as measured by howRu was greater than that measured by EQ-5D, relative to that measured by OHS or OKS. For hip replacements, the correlation for change measured by howRu and OHS was r = 0.77 (0.66-0.85). The corresponding correlation for change measured by EQ-5D Index and OHS was r = 0.64 (0.63-0.64). For knee replacements the correlation between change in howRu and OKS was r = 0.86 (0.75-0.92); between EQ-5D Index and OKS r = 0.59 (0.58-0.60). CONCLUSIONS:For hip and knee replacement, the outcome measured by howRu was more highly correlated with that measured by the condition-specific Oxford Hip and Knee Scores than were EQ-5D Index or EQ-VAS. The magnitude of change before and after surgery was also greater.