If you are riding to commute, recreation or just to stay fit, i would forgo the clipless pedals. I would try what fixed gear riders mostly do, they use foot retention straps that dont keep your foot so solidly in one position like clipless pedals and shoes. I ride for fitness and recreation and I ride fixed I have foot retention on both my fixed gear bikes, straps, I have had no trouble at all with my knees since riding fixed for about a year and half and I am 61. I ride 100 to 120 miles a week.