The question remains as to whether aquatic physical therapy is superior to land-based physical therapy for OA. Other authors have failed to demonstrate any additional benefit of hydrotherapy over home exercises or over a gym-based strengthening program for people with OA; those results may have been related to the aquatic physical therapy program content in those published trials. Given the association of quadriceps femoris muscle strength with pain severity and physical function in OA it is essential that aquatic programs incorporate a resistance training intensity comparable to that of land-based programs. To increase resistance for muscle strengthening in the water, it may be necessary to further decrease the depth of immersion with closed-chain exercises, to use floats in buoyancy-resisted positions, or to increase resistance from turbulence by increasing speed or surface area (with the addition of flippers or boots) with open-chain exercises. Further studies of aquatic physical therapy should aim to refine program content by maximizing the use of the hydrostatic and hydrdynamic properties of water and thus the potential benefits of aquatic physical therapy for people with
lower-limb OA. Future research also should be directed toward evaluating the characteristics of people who respond to land- and water-based exercises, as it is possible that certain types of exercise regimens are more suitable for particular sub groups of people