Water-based exercises are recommended for people with osteoarthritis (OA), due to the beneficial effects on physical function, quality of life and symptom reduction. However, the effects on muscle strength are still controversial. The aim of this review was to assess and compare the effects of aquatic exercise programs on muscle strength and physical function in people with OA. A systematic search was performed at Pubmed, Scopus and Web of Science databases. Clinical trials with interventions involving aquatic exercises for individuals with OA were included. The methodological quality of the studies was evaluated using the PEDro scale. 296 studies were found and twelve were selected: six studies comparing water-based exercises with land-based exercise, and six comparing water-based exercise groups with the control group. Exercise programs included muscle strengthening, aerobic, balance, flexibility and stretching exercises. Duration of the program, weekly frequency, intensity and progression varied between studies. Beneficial effects of aquatic exercise were found on physical function. However, only two of five studies that assessed muscle strength observed positive effect of aquatic exercise. Although it is difficult to compare studies and establish guidelines for the standardized protocol formulation, it was observed that water-based exercises can be effective on improving physical function and increasing muscle strength, since they are well-structured, with exercise intensity and overload controlled.