First, strengthen and stretch the muscles that support the knees. The calf muscles and shins also need to be stretched and strengthened as they contribute to the structure of the leg. Leg curls strengthen the hamstrings and can be done on a leg curl machine or with ankle weights. Select a weight that allows you to complete two or three sets of eight or twelve repetitions. Follow steps 3 and 4 above.
Leg extensions strengthen the quadriceps.
Perform two or three sets of eight or twelve repetitions for each leg. Do not increase weights too quickly because you may injure your knees. Pause briefly and then slowly lower to starting position. Throughout the exercise, support your back and sit straight. Again, make sure the weight stack does not touch in-between repetitions.