Thorborg K, Hölmich P, Christensen R, et al. The Copenhagen Hip and Groin Outcome Score (HAGOS): development and validation according to the COSMIN checklist (Br J Sports Med 2011;45:478–491). In table 2, in rows A1 Walking down stairs and A2 Walking up stairs the data was inadvertently swapped. The journal apologises for this error.