Hello, As the pain is in his knee and feet I wish to know If it s radiating in nature. If so we can suspect it to be nerve entrapment. If the pain is dull ache then due to arthritis of the knee it may be caused. Regarding the feet you mentioned about the plantar fasciitis, have you been diagnosed before with it or it s just a speculation. I will try to give a solution which covers all the three joints. As history is quite not clear. Your age is close to 60, so we can expect some degenerative changes in the joints of the spine, hip and knee. You can start exercising which includes the core stability, spinal muscle strengthening, hip strengthening, static Quadriceps and static Hamstring, ankle toe movements. This exercise are in general for the pain in the hip and ankle. If you have a specific diagnosis with plantar fasciitis than stretching of the calf muscle and balance board training should help. Due to single joint trouble like knee or ankle or back, there will be a change in the biomechanics of the joint and the muscles may undergo some physiological changes. Doing exercises will help improve the overall strength and also allow the joint space to be maintained. By which the joint pain can be reduced. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Jay Indravadan Patel, Physical Therapist or Physiotherapist