Post knee replacement surgery rehabilitation

A patient’s guide to rehabilitation post knee replacement surgery

Colin Walker Orthopaedic Knee Specialist

Frank Gilroy BSc MSCP

Georgia Bouffard Student Physiotherapist

Anatomy of the knee

The knee is the largest joint in the body. It must be strong to support your body weight and flexible to allow bending and twisting movements. It joins the femur and tibia bones surfaces which are covered with cartilage to allow smooth movement between the two bones. The joint is surrounded in a synovial membrane that produces synovial fluid which lubricates, nourishes and reduces friction within the joint. Two C-shaped pieces of cartilage, called the menisci, sit between the femur and tibia for shock absorption.

The quadriceps at the front of the thigh straighten the knee. The hamstrings and calf muscles both bend the knee. Two pairs of ligaments are responsible for stabilising the knee, the cruciate ligaments and the collateral ligaments. The patella, known as the knee cap, sits on the front of the knee and acts an anatomic pulley for the quadriceps muscle.

Why do you need a knee replacement?

Knee replacement surgery is suited for people suffering from advanced arthritis or damage to the joint by trauma, fractures, or congenital deformities. The procedure may be recommended when your ability to walk is limited, pain is experienced at night, and your quality of life is affected. Your specialist will likely recommend non-operative treatment before surgery. X-ray and MRI scans will confirm that arthritis has caused significant changes to the joint and that the articular cartilage has worn down to the bone. The surgery aims to reduce pain and improve function.

About the surgery

Knee replacement, also called arthroplasty, is a surgical procedure to resurface a knee damaged by arthritis. It is frequently performed, with over 75000 procedures carried out in the UK very year, and highly successful. There a two types of knee replacements. A total knee replacement completely replaces the articular surfaces of the femur, tibia and patella and removes the cruciate ligaments. A partial knee replacement is possible if only one part of the knee is damaged. The healthy parts of the articulation surface and the cruciate ligaments are preserved improving function and recovery post-surgery.

ou will be seen in a pre-admission clinic prior to your surgery. On the day of the surgery, you will receive a spinal anaesthetic that will put you to sleep for the entire operation. An 8 to 10-inch incision is made down the front of the knee and the patella is rotated to the side to allow access to the joint. Damaged bone and cartilage is removed and replaced with a metal prosthesis. Most commonly, cement is used to fix the new prosthesis onto the remaining bone, however a non-cement method uses a porous surface onto which the bone grows. A flexible cushion made of polyethylene is attached on top of the tibia surfaces to act as shock absorber. The wound is then closed using stiches or clips, and a dressing is applied

What to expect after the surgery?

Knee replacements have a limited life expectancy before they will wear out or become loose. Applying excessive stress on the prosthesis through running, manual work or high impact sports will decrease its longevity. The prosthesis can be replaced but this is a complicated procedure.
After the surgery, you should expect freedom of pain and good mobility within your knee. Knee replacements will allow you to fully straighten your knee but they may not allow you to bend as far as a natural knee. Regular exercise will enable you to regain strength, movement and function.

Pre-operative rehabilitation

Arthritis and age weakens the musculature surrounding the joint. It is important to exercise these muscle before the operation because swelling and pain post-surgery will affect your ability to your exercises post-op.

Exercises must be performed 5 times a week, ideally 4-6 weeks prior to the surgery. Repeat exercises until muscle is fatigued, aim for 10-20 repetitions. Hold stretches for 30 seconds and repeat 3 times.

  1. Cardiovascular exercises:

    To improve your general cardiovascular fitness, do 10 to 20 minutes of cycling, walking or swimming before your exercises.

2. Stretching:

  • Calf stretch: stand facing a wall, step one foot back and lean forwards. Keep your leg straight and both hips facing the wall. Hold
    for 30 seconds on both legs.
  • Hamstrings stretch: lie on your back, lift one leg up towards your trunk and apply stretch by straightening your knee.

3. Flexibility exercises:

  • Straightening/extension: with a rolled-up towel under your ankle, allow the weight of your leg to straighten your knee. Hold for as long as comfortable, aim for 10
  • Bending/flexion: Sitting or lying, use a towel or strap to bend your leg as far as it will go.

4. Strengthening exercises:

  • Straight leg raises: keeping your knee straight, lift your leg up. Progression: tie TheraBand around your ankles or attach an ankle
  • Inner-range quads: place towel under your knee and straighten your knee by lifting your heel off the bed.
  • Step-ups: lead with your operated leg.

  • Chair leg strengthening: bend your leg as far as possible, then straighten it fully.
  • Chair squats: slowly lower yourself into the chair, making sure you don’t “fall” onto the seat and you are using both legs equally. Stand up and repeat.

5. Proprioception and balance

  • 1 leg stand: Lift one leg up from the floor and try to balance (stand near to a wall for safety). Repeat on both legs.
  • Tandem walking: Walking slowly along a line, placing one foot in front of the other (as if on a tightrope). Try to keep to the line.
  • Heel-raises: holding on the wall, lift your heels off the wall and balance for 5 seconds.

Post-operative rehabilitation
Immediately post-operation: Day 0-2

PROTECTION– To optimise healing process
REST– Walk with crutches and progress to a stick as able
ICE– Apply ice for 20minutes every 2 hours. This can be within an ice pack or pack of frozen peas wrapped in a cloth before applying to the skin
COMPRESSION– To reduce swelling around your knee during the day and remove at night time
ELEVATION– Elevate your knee above the height of the hips in resting to reduce the blood flow to the area which in turn reduces the swelling

How to use your crutches?

  • Walking with crutches: Place the crutches forward with the operated leg and then step through with the other leg by itself.
  • Ascending stairs with crutches: Hold onto the rail with one hand, and both crutches in the other hand. Using the hand rail and pushing through your crutches lift yourself up onto the step, and follow with your operated leg.
  • Descending stairs with crutches: Hold onto the rail and both crutches in the other hand. Lower your operated leg onto the step, and using the crutches and handrail to support your weight step your other leg down.
  • Sit to stand with crutches: To sit down remove arms out of the crutches and hold both on one side and sit. To stand up hold crutches on one side and push through the chair’s arms.

Immediately post-operation (IPO) exercises:

Repeat all exercises 10 times, 4 times a day. If these are uncomfortable or your leg feels tired, do not push through pain. Do what you can, and gradually increase repetitions as you get stronger.

  1. Flexibility exercises
  • Ankle pumps: point your toes, and flex your ankles.
  • Straightening/extension:
    With a rolled towel under your ankle, let the weight of your leg straighten your knee. Hold for as long as comfortable, aim for 10 minutes.
  • Bending/flexion:
    Using a towel or strap bend your knee as far as possible. This may feel uncomfortable at first, but don’t worry you are not doing any damage to your knee.

2. Strengthening exercises:

  • Quadriceps contraction:
    Lying on your back with legs straight, flex your ankles and push your knees down firmly against the bed to contract your thighs. Hold for five seconds, then relax for five seconds.
  • Glute contraction:
    Lying down squeeze your buttocks firmly together. Hold for five seconds then relax
    for five seconds.
  • Straight leg raises: Keeping your knee straight, lift your leg up from the bed.

During your rehabilitation, movement in your knee will be measured in degrees. Flexion is how much you can bend your knee and extension is how much you can straighten it.

Phase 1: Week 1-2

• Safe independent ambulation with walker or crutches as needed
• 90 degrees of flexion, 0 degrees of extension
• Control of swelling and pain levels.

Guidelines for phase 1:

– No kneeling or sitting crossed-legged
– Weight bearing as tolerated 2 crutches or rollator frame
– Continue applying ice pack, for 20 minutes, 3 times per day
– Continue with previous exercises, add on exercises for weeks 1-2

Exercises for phase 1:

Continue with IPO exercises

• Ankle pumps
• Straightening/extension
• Bending/flexion
• Quadriceps contraction
• Glute contraction
• Straight leg raises

Add on the following exercises:

  • Hip abduction: in standing or side-lying raise your leg to the side.
  • Chair exercise: sitting on a chair bend your
    leg as far as it will, then straighten it fully.

Phase 2: Weeks 2-4

Criteria to enter phase 2:
• 0-90 degrees movement
• Able to perform a straight leg raise
• Minimal pain and swelling
• Independent ambulation/transfers

• Increase movement to 100 degrees of flexion and 0 degrees of extension
• Establish return to functional activities
• Wean off walking aids

Phase 2 exercises:

Continue with the following exercises from phase 1:

• Straightening/extension
• Bending/flexion
• Hip abduction
• Chair exercise

Add on the following exercises:

  1. Flexibility exercises
  • Knee hanging: lying on your front, have your ankles hanging off the edge of the bed. Hold for as long as comfortable, aim for up to 5 minutes.

2.Strengthening exercises

• Straight leg raise with TheraBand: Tie a green TheraBand around your ankles, and raise your leg against the resistance. If this is too difficult, continue the exercise without the TheraBand.

• Inner-range quad exercise with TheraBand: place a towel under your knee and lift your leg off the bed. Tie a green TheraBand around your ankles, and raise your leg against the resistance.

• Hamstrings stretch: stand in front of a wall or furniture that you can lean onto. Straighten your operated leg in front of you, bend your other leg and lean forwards. You should feel a stretch at the back of your thigh.

• Calf stretch: Facing a wall, step your operated back behind you. Bend your front leg keeping your back leg straight.

Phase 3: Weeks 4-6

Criteria to enter phase 3:
– 100 degrees of flexion and 0 degrees of extension
– Walking without any walking aids

• 110 degrees of flexion and 0 degrees of extension
• Improve balance and proprioception

Exercises for Phase 3:

• Continue with the following exercises:
• Straightening/extension
• Bending/flexion
• Hip abduction
• Progress straight leg raises and inner-range quad exercise to a yellow TheraBand.

  1. Exercises for function
  • Sit-to-stand practice: repeatedly practice sitting down in chair in a controlled manner, making sure you don’t “fall” into the chair and you are using both legs equally. Count to 3 when sitting down,
    and to 2 when standing up
  • Step-ups: practice stepping up onto a step, leading with the
    operated leg.

2. Balance and proprioception exercises:

  • 1 leg stand: Holding onto a wall, lift one leg off the floor. Try to leg go off the wall. Hold for 10 seconds
  • Tandem walking: walk on a straight line
  • Heel-raises: holding on the wall, lift your heels off the wall and balance for 5 seconds. Try to let go of the wall and find your balance.

3. Cardiovascular fitness training:

• Start hydrotherapy program if consultant has given all clear.

• Aqua-jogging 2-3 a week, for 20-30 minutes. The buoyancy of the water will allow you to build strength without applying stress to the joint.

• Start cycling on an exercise bike for 10 minutes 3 times per week

Phase 4: Weeks 6-12

Criteria to enter phase 4:

  • Between 100 and 110 degrees of flexion, 0 degrees of extension
  • Able to perform leg exercises using a yellow TheraBand


  • Improve cardiovascular fitness

    Continue with phase 3 exercises:

  • Increase cycling to 20 minutes 3-time weekly
  •  Progress to red TheraBand if you feel the yellow one is becoming easy.

DISCLAIMER: You must consult a chartered physiotherapist or your specialist before embarking on this program. If you do experience pain or discomfort as a result of any of the exercises, stop immediately and speak to a health professional.