The Nike Free line was conceived as therapeutic from the start. The idea, which predates the minimalist running movement, is that runners can strengthen the musculature of their feet and lower legs by wearing shoes that are flexible and as light as racing flats, and that let you feel the ground instead of shielding you from it. Getting your foot and leg muscles back into balance might be just what your PT orders for your knee pain, while the combination of stability and cushioned firmness that the Free RN Flyknit 2018 offers has proved effective for many runners.