ACL INJURY

Post Knee Arthroscopy Exercises
ACL Injury
(Source: Physical Theraphy: About.com)

After undergoing knee arthroscopy, it is important to begin exercising your knee immediately to restore strength and full range of motion. Initial exercises should be non-weight bearing in nature, and should focus on gentle strengthening of the muscles surrounding the knee as well as increasing joint range of motion.
As always, you should discuss starting any exercise program with your orthopedic surgeon prior to initiating it. Most physicians will approve an early rehabilitation program, however others may ask you to wait a week or so after your procedure.
Initially, you will experience some swelling and discomfort in the knee for a few days post operatively. You will most likely be given a prescription for pain medication and an anti-inflammatory drug to help alleviate these symptoms.
You should expect to feel a gentle stretch while performing your beginning exercises, but you should not experience any pain. Any activity that causes significant discomfort should be stopped immediately. It is also a good idea to ice and elevate your leg after performing these exercises to decrease any increase in swelling.
The following exercises are appropriate for immediate post-arthroscopy rehabilitation. The movements should be gentle and steady. Bouncing or over-stretching should be avoided. Read on to review these four exercises.

Lay on your back on a flat surface. Place a rolled towel under your ankle between you and the surface. Push your ankle down into the towel roll. This will cause your knee to straighten as it raises off the surface you are laying on. Straighten your knee as much as possible and hold the position for five seconds. (Avoid any type of bouncing motion!) Relax and repeat 10 more times.

Exercise 2 - Hamstring Contraction
Lie on your back with your knees bent in a 10 to 15 degree angle. Without moving your leg, pull your heel into the floor. This will cause the muscles on the back of your thigh to contract. Hold this for five seconds. Relax and repeat 10 more times.

Exercise 3 - Gluteal Sets
Lie on your back with your knees bent in a 10 to 15 degree angle. Squeeze your buttock muscles together. Hold for five seconds. Relax and repeat 10 more times.

Exercise 4 - Straight Leg Raises

Lay on your back on a flat surface. Bend the knee of your uninvolved leg (the one that wasn't operated on) to a 90-degree angle with your foot flat on the surface. Keep your involved leg straight without the knee bent. Slowly lift the involved leg six inches off the floor. (by contracting the front thigh muscles). Hold for five seconds. Slowly lower your leg to the floor. Relax and repeat 10 more times. (The knee of the raised leg should remain straight throughout this exercise. Focus on lifting by using the muscles on the front of your hip joint.)