What kind of weight vest do you use? How heavy? I was told it should not exceed 10% of body weight—have you heard the same? I was using an REI-fitted backpack filled with flat ankle weights in an interior pocket while using its chest and shoulder straps, but apparently it put too much torque on my hip flexors which stressed my knees and I have been paying the price since. I have stopped carrying any weight, reduced my mileage by 2/3, stopped doing lower body RT, stopped using elevation on a treadmill, and stopped using a stair climber, with no relief. Before using the weighted pack, I was doing all of this with no knee pain. 69YO female w severe osteoporosis in lumbar spine, normal BMI, otherwise in good shape. TIA.