Fig. 2

a Timed Up and Go Test (TUGT): results are presented in seconds. b Thirty-second Chair Stand Test (CST): results are presented as number of cycles. c Numeric pain rating scale (NPRS). Pre-op (Leg 1): when patients were discharged from pre-operative physiotherapy. D0 post-op (leg 1): at the first post-operative rehabilitation, in the same-stage group and the first knee in two-stage group. D/C from PT (leg 1): when patient was discharged from physiotherapy for the first knee in the two-stage group. Pre-op (leg 2): when patient was discharged from pre-operative physiotherapy for the second knee in two-stage group. This time point did not exist for the same-stage group. D0 post-op (leg 2): the first post-operative rehabilitation in the second knee in the two-stage group. For the same-stage group, this time point is the same as D0 post-op (leg 1). D/C from PT the moment when the patient was discharged from physiotherapy (PT) at the end of all rehabilitation. The dotted line with the arrow indicates the time spared in same-stage, bilateral total knee replacement (TKR) group