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ACL Surgery Rehabilitation


This is just as important as rehab after the surgery. If you don’t have strength and a good range of movement in the knee before the surgery it will be very hard to get it back afterwards. It also allows you get started on your recovery earlier than if you wait. You should work with your physio to achieve a full range of movement (both flexion and extension) as well as quadriceps and hamstring strengthening exercises. Avoid any running or sporting activities that could allow your knee to collapse under you.


The graft is at its strongest on day 1 post op, of course the knee will be sore from the surgery, but this will settle fairly quickly. The new ligament actually gets weaker as new tissue grows into the graft substance. When the knee is feeling great at 8-10 weeks post op, the graft is actually at its weakest. Thereafter the graft will get stronger and stronger for a full 12 months after the surgery at which point it’s roughly the same strength as the original native tissue before the injury.

First 6 weeks

Start slowly, work regularly, persist, aim for gradual progression with slight improvement every second day.

Aim to get “the knee fit”, not the rest of the body

If the knee is swelling a lot after activity and is restricting movement you have done too much and need to ease off next time. Take the anti-inflammatories that have been prescribed and rest the knee until the swelling resolves.

Order of goals and exercises

  • Restore extension, (straightening) of knee.
  • Reduce swelling.
  • Start quads strengthening using “closed chain” exercises.
  • Restore flexion (bending) of knee.
  • Gentle controlled hamstring stretches.
  • Start balance work (proprioception).
  • Gentle exercise bike (not regular bike though) or similar for functional strength and cardio.

Restore full extension

Heel prop

Passive extension of the knee by using a rolled towel under the ankle.

  • Remove the knee immobilizer from your knee every 2 - 3 hours while awake.
  • Position the heel on a pillow or rolled blanket with the knee unsupported.
  • Passively let the knee sag into full extension for 10 - 15 minutes. Relax your muscles, and gravity will cause the knee to sag into full extension.

This exercise can also be done by sitting in a chair and supporting the heel on the edge of a stool, table or another chair and letting the unsupported knee sag into full extension.

Leg extensions

Active-assisted extension is performed by using the opposite leg and your quadriceps muscles to straighten the knee from the 90-degree position to 0 degrees.

Hyperextension should be avoided during this exercise. Use the non-injured leg to help straighten the knee.

Reduce swelling

  • Take the anti-inflammatories for the first 2 weeks post op.
  • Ice icepacks intermittently especially after exercise.
  • Don’t sit with the leg hanging down for prolonged periods.
  • Remove the brace every few hours at least and move the knee, foot and ankle around.

Exercising Quadriceps

You should start quadriceps isometric contractions with the knee in the fully extended position as soon as possible.

Static Quadriceps Contraction (Thigh Squeeze)

  • Lie or sit up in bed with your legs straight out in front of you and pull you toes upwards. Tense the thigh muscles to try and push the back of your knee down into the bed.
  • Hold for 10 seconds and repeat 10 times.
  • Do 5 sets of 10 repetitions 3 times a day.
  • This exercise helps to prevent shut down of the quadriceps muscle and decreases swelling by squeezing fluid out of the knee joint.

Begin straight leg raises (SLR) with the knee immobilizer on 5 sets of 10 repetitions 3 times a day.

  • Start by doing these exercises while lying down.
  • This exercise is performed by first performing a quadriceps contraction with the leg in full extension. The quadriceps contraction "locks" the knee and prevents excessive stress from being applied to the healing ACL graft.
  • The leg is then kept straight and lifted to about 45-60 degrees and held for a count of six.
  • The leg is then slowly lowered back on the bed. Relax the muscles.
  • Remember to relax the muscles each time the leg touches down.
  • This exercise can be performed out of the brace when the leg can be held straight without sagging (quads lag). Once you have gained strength, straight leg exercises can be performed while seated.
  • Remember – always start with the leg out straight!

Start Partial Squats

  • Place feet at shoulder width in a slightly externally rotated position.
  • Use a table for stability, and gently lower the buttocks backward and downward.
  • Hold for 5 seconds and repeat.
  • Do 3 sets of 10 repetitions each day.

Achieve good flexion range

Passive flexion (bending) of the knee to 90 degrees.

  • Sit on the edge of a bed or table and letting gravity gently bend the knee.
  • The opposite leg is used to support and control the amount of bending.
  • This exercise should he performed 4 to 6 times a day for 10 minutes. It is important to achieve at least 90 degrees of passive flexion by 5 - 7 days after surgery.

Heel slides are used to gain final degrees of flexion.

  • Pull the heel toward the buttocks, flexing the knee. Hold for 5 seconds.
  • Straighten the leg by sliding the heel downward and hold for 5 seconds.
  • Heel slide – leg is pulled toward the buttocks.
  • In later stages of rehabilitation, do heel slides by grasping the leg with both hands and pulling the heel toward the buttocks.

Exercising Hamstrings

  • Slow gentle stretches of the hamstrings early will help ensure that they heal up at the correct length, not short and stiff. Be very careful though and don’t “push through” hamstrings pain.
  • The hamstring muscles need about 6 weeks to heal, and excessive hamstring stretching during this period can result in a "pulled" hamstring muscle and increased pain.
  • Unintentional hamstring stretching commonly occurs when attempting to lean forward and put on your socks and shoes, or when leaning forward to pick an object off the floor.

6-16 weeks

  • Ongoing quads and start gentle hamstring strengthening in gym (use squats, lunges, leg press, deadlifts).
  • No weighted leg extensions! Add calf strengthening if you like.
  • More balance exercises.
  • Use exercise bike, incline treadmill, rower, stepper, elliptical or skipping to improve cardio-respiratory fitness.
  • No open chain quads exercise or running yet - the graft is very weak at this stage and will stretch and get loose if stressed.

4-6 months

  • Keep going on the gym work.
  • Start very gentle jogging on flat, even surface, slow treadmill or mini trampoline, build up slowly to regular straight-line jogging.
  • No cutting or sprinting.
  • No open chain leg extensions.

6-9 months

  • Start agility training.
  • Add gentle, controlledchanges of direction.
  • Build up to sport specific training drills over next 2 months.
  • Then start regular sport training, avoid contact and cutting at first.

9+ months

  • May add open chain quads strengthening (if you really must!).
  • Full on” unrestricted sport training.
  • If able to train for 3 weeks without problems may return to play (consider change of sport or position to reduce risk of recurrent injury).