As with any exercise regimen, and especially for post-operative recovery, seek the advice of a physician who specializes in sports medicine and injury before beginning. Your doctor will be able to tell if your knee is ready for exercise.
Use low-impact aerobics to warm up the muscles. Walking or slowly pedaling on a bicycle (or stationary bike) will warm up your muscles and loosen the ligaments and tendons before you exercise. This will prevent other injuries as well as knee aggravation.
Stretch before exercising. Three main muscle groups (hamstring, calf and quadricep or "quad") must be stretched before strength training.
To stretch the calf, place your left foot behind you and your right in front of you. Lean over your right foot and hold for 10 seconds, making sure both feet remain flat on the ground. Do the same for your right foot.
To Stretch your hamstring, place your feet together and lean over, but do not touch your toes. Hold for 10 seconds, then repeat three to five more times.
To stretch your quadricep, stand facing a wall and raise your left shin up toward your buttocks, gripping the toes lightly with your left hand and pulling. Hold for 10 seconds and stabilize yourself by placing your right hand on the wall (if necessary). Repeat for your right leg.
Perform simple exercises to strengthen your muscles.
To strengthen calf muscles, stand with your feet together and raise yourself up onto your toes. Slowly raise and lower your body, adding weight as your muscles regain strength by holding barbells or dumbbells. Repeat 10 times.
To strengthen your hamstring, place ankle weights on your ankles and lay face down on a bench. Raise your legs toward your buttocks slowly. Repeat 10 times. You may add heavier weights as you regain strength.
To strengthen your quads, lunges work best. Step forward with your left leg and bend at the hips over your left leg. Straighten up and step forward with your right leg and repeat. Repeat 10 times per leg, adding weight as your strength increases by holding dumbbells in your hand.