Discussion
Older adults who underwent TKR surgery participated in the 4-month home-based intervention using customised exergames, which improved their mobility more than those who exercised by the standard home exercise protocol. In addition, early satisfaction seemed to be more frequent in the IG. In both groups, there were positive changes in knee-related pain and physical function, including knee-related function, walking and lower extremity performance and strength over the 4 months; however, there were no statistically significant differences between the groups. This study’s results align with earlier studies investigating the use of exergames in enhancing physical function and pain in post-TKR rehabilitation.33 34
When observing changes in mobility using the TUG, improvement was greater in the IG than in the CG, both in the middle and at the end of the intervention. For example, a similar difference between guided high-intensity and low-intensity training after TKR has not been observed.35 The difference between IG and CG may be due, for example, to how the exergames may steer the training in a more progressive and goal-oriented direction than the instructions given for standard exercise. Moreover, it should be noted that the TUG did not change in the CG in the 2-month and 4-month follow-up points.
There were no intergroup changes when assessing changes in knee-related function and pain using the OKS. Positive changes were observed in both groups, indicating normal healing after TKR. When evaluating 95% CI, it can be speculated that when increasing the number of participants, CIs would narrow; thus, there may be significant differences in change between the groups.
When evaluating the clinical relevance of changes in knee-related function and pain using the OKS, the mean change in both groups was more than the estimate of the minimal clinically important change (MCIC) in the OKS in patients with TKR.31 In addition, a change in the OKS of 11 points or more 6 months after TKR has been related to satisfaction with the surgery.36 In the IG, this limit was already exceeded at 4 months, and 100% of the participants were either satisfied or very satisfied with the operated knee. In the CG, the percentage was 74%. The TUG MCIC has not been validated in patients with TKR. However, at 4 months, the mean change in the IG was similar to the TUG MCIC in lumbar surgery patients37 and thus may also support the observed early satisfaction. Moreover, gamification may affect patients’ expectations and experience of TKR and, thus, overall satisfaction.38
At 4 months, there were no significant intergroup changes in physical function or pain in the secondary outcomes. However, the pain intensity and lower extremity performance in both groups and walking in the IG changed slightly positively. When observing the results of the muscle force tests and knee ROM measures, there were no within-group changes in knee extension or knee flexion muscle force or knee extension ROM. The only negative change was observed in the knee flexion ROM in the CG, while in the IG, there was neither a negative nor positive change. Bade et al,39 who assessed patients with TKR following a standard rehabilitation programme, observed similar within-group results at 3 and 6 months after surgery; the knee flexion ROM remained below the baseline level.
The participants’ self-reported adherence to home exercise during the intervention was similar between the groups. However, the volume of exergaming and standard exercise varied widely between the participants over the intervention period. This may reflect the positive changes in physical function and pain achieved within 2 months, which may lower interest or motivation for rehabilitation. Moreover, variation may reflect interest or loss of training through novel games or individuals’ choices to exercise in the preferred way.6 In addition, this may be due to an increase in other self-reported PA,40 observed in the IG and is a positive change compared with the finding that PA may remain low during the first months after TKR surgery.41 42
The strength of this study is the accurate design and implementation of a dual-centre RCT.16 The randomisation was successful, and outcome variables selected in collaboration with researchers, orthopaedists and physiotherapists were validated and commonly used to measure the physical function and pain of patients with TKR.22 26 43–47 Self-employed therapeutic exercise implemented at participants’ homes ensured that despite the limitations caused by the COVID-19 pandemic in 2020, participants could continue therapeutic exercise in the assigned group without compromising their rehabilitation.
Study limitations
This study has several limitations. First, the number of participants was low, and half of the planned sample size was achieved in 2020 due to COVID-19. Second, assessors were not blinded after the baseline assessment because of the nature of the interventions and game-specific questionnaires collected from the exergame group. This may pose a risk of bias to the physical function follow-up assessments performed by a research physical therapist. Finally, due to COVID-19, some of the outcomes gathered by physical tests were not measured in this study. Because of the small sample size, the study results of physical function are indicative and will limit the generalisation and interpretation of the results. Future studies should aim to conduct similar studies among a larger cohort of participants.