To treat arthritis in the hips and knees with physical therapy, start with low-impact exercises like cycling or swimming to reduce joint stiffness and improve mobility. Strengthen surrounding muscles with targeted exercises like leg lifts, step-ups, and squats to support the joints. Stretching exercises for the hamstrings, quadriceps, and hip flexors improve flexibility. Use heat therapy before exercise to ease stiffness and cold therapy afterward to reduce inflammation. Gradually increase activity levels while avoiding joint strain.