Objective: We aim to predict the probability of a benefit from two contrasting exercise programs for a woman with a new diagnosis of mild knee osteoarthritis (OA). The short and long-term effects of aquatic resistance training (ART) and high-impact aerobic land training (HLT) compared with the control will be estimated.

Methods: Original data sets from two previously conducted randomised controlled trials (RCT) were combined and used in a Bayesian meta-analysis. Group differences in multiple response variables were estimated. Variables included cardiorespiratory fitness, dynamic maximum leg muscle power, maximal isometric knee extension and flexion force, pain, other symptoms and quality of life. The statistical model included a latent commitment variable for each female participant.

Results: ART has 55% - 71% probability of benefits in the outcome variables and as the main effect, the intervention outperforms the control in cardiorespiratory fitness with a probability of 71% immediately after the intervention period. HLT has 46% - 63% probability of benefits after intervention with the outcome variables, but differently from ART, the positive effects of physical performance fade away during the follow-up period. Overall, the differences between groups were small and the variation in the predictions between individuals was high.

Conclusions: Both interventions had benefits but ART has a slightly higher probability of long-term benefits on physical performance. Because of high individual variation and no clear advantage of one training method over the other, personal preferences should be considered in the selection of the exercise program to ensure highest commitment to training.