Knee Replacement

by PhysioAdvisor Staff

InjuriesKnee InjuriesKnee Replacement

(Also known as Total Knee Replacement, Total Knee Joint Replacement, Knee Replacement Surgery, Total Knee Arthroplasty)

What is a knee replacement?

A knee replacement is an invasive surgical procedure that is used to remove a diseased knee joint (most commonly due to osteoarthritis) and replace it with an artificial joint or prosthesis.

The knee joint is a hinge joint that primarily comprises of the union of two bones: the long bone of the thigh (femur) and the shin bone (tibia) (figure 1). Between the bone ends are 2 round discs made of cartilage called the medial (inner) and lateral (outer) meniscus (figure 1). Articular cartilage also lines the joint surfaces. The articular cartilage and menisci act as shock absorbers, cushioning the impact of the femur on the tibia during weight-bearing activity. The knee cap (patella), situated at the front of the knee, also forms a joint with the femur (i.e. the patello-femoral joint). In addition, strong ligaments and connective tissue hold the bones of the knee together, giving it stability.

Relevant Anatomy for a Knee Replacement

Figure 1 – Relevant Anatomy for a Knee Replacement

Structures within the knee (such as the cartilage or bony joint surfaces) may be damaged due to overuse, trauma or certain conditions (e.g. rheumatoid arthritis, tumours etc.). This may lead to degenerative changes within the knee or osteoarthritis. These injuries may be beyond the body’s healing capacity and if severe enough may warrant knee replacement surgery to treat the condition. This may be particularly indicated in patients with severe knee osteoarthritis who have not responded to appropriate physiotherapy treatment and rehabilitation and have severe pain and disability due to their knee condition.

A knee replacement is usually performed under general anaesthetic or occasionally spinal anaesthetic and usually takes approximately 2 – 4 hours. Medication such as antibiotics are usually administered prior to surgery to prevent potential complications such as infection.

Surgery usually involves an incision of approximately 30cm down the front of the knee / knee cap. Soft tissue such as muscle is moved to expose the knee joint, followed by cutting and removal of the damaged joint surfaces of the tibia and femur. The prosthesis is then fixated into position with the use of bone cement to hold the prosthesis in place. The knee cap is removed if required and replaced with a prosthetic ‘button’. Ligaments and muscles are rearranged and a drainage tube is placed into the wound. The wound is closed with stitches or clips. Knee replacement surgery without complications usually involves a 7 – 10 day hospital stay.


Indications for a knee replacement

Knee replacement surgery may be indicated in patients with certain knee conditions, particularly those that do not respond to appropriate physiotherapy treatment and rehabilitation, and, have severe pain and disability.

Some of the more common knee conditions treated with a knee replacement include:

  • Severe osteoarthritis
  • Rheumatoid arthritis
  • Ligament damage or infection that leads to severe osteoarthritis
  • Gout
  • Avascular necrosis (death of bone following loss of blood supply)
  • Bone dysplasias (abnormal growth of bone)
  • Certain tumours

An orthopaedic surgeon can assess a patient and determine the suitability of a knee replacement based on a number of factors. Some of these may include:

  • Injury diagnosis and severity
  • Degree of pain and disability experienced by the patient
  • Patient age, occupation and activity levels
  • Expected symptomatic and functional improvement following surgery
  • Medical history of the patient
  • Potential complications of surgery
  • Cost

Signs and symptoms following a knee replacement

Following knee replacement surgery, symptoms vary significantly from patient to patient depending on a number of factors. These factors may include:

  • the severity of injury prior to surgery
  • degree of trauma to tissue during surgery
  • type of pain relief or anti-inflammatory medication used
  • strength and flexibility of the knee prior to surgery
  • age of the patient
  • pain perception and previous experiences
  • quality of rehabilitation following the procedure

A small percentage of patients may experience only minor symptoms following a knee replacement and may only notice stiffness and minor soreness. This is often the case in:

  • younger patients
  • patients who have excellent strength and flexibility of the knee prior to surgery
  • those patients using appropriate medication
  • patients who adhere to appropriate rehabilitation under physiotherapy guidance

Typical symptoms

Patients usually experience significant swelling, pain and knee stiffness with symptoms ranging from mild to severe. Pain may be felt in the front, back or sides of the knee or occasionally the thigh, calf, ankle or foot. Symptoms typically increase with:

  • excessive weight bearing activity (especially walking up or down hills or on uneven surfaces or standing still for prolonged periods)
  • excessive bending, straightening or twisting of the knee
  • climbing up or down stairs
  • attempting to kneel
  • repetitive, prolonged or forceful squatting, lifting or carrying.

The patient may also walk with a limp or be unable to weight bear due to pain. Symptoms may also increase with rest and may present as an ache, pain or stiffness that is particularly prominent at night or first thing in the morning.

Tenderness is usually experienced when firmly touching the knee, particularly on the surgical scars. The knee may also feel weak or unstable and in some cases may give way or feel like it’s going to collapse with certain movements. Bruising (particularly in the first few weeks), pins and needles or numbness may also be experienced. These symptoms will vary in severity from patient to patient.


Treatment following a knee replacement

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Prognosis following a knee replacement

Approximately 90% of patients who have a knee replacement experience less pain and improved mobility compared to before surgery. Recovery times vary significantly from patient to patient. Rehabilitation typically lasts 3 – 12 months or longer. It is important to note that a knee replacement will not function the same as a normal knee.

Some patients may require an extended period of rehabilitation following surgery. This may be the case in patients with more severe knee injuries, with subsequent severe weakness or knee stiffness prior to surgery, or in those who experience other surgical complications such as infection, or damage to local blood vessels or nerves. Following surgery, patients who do not rest adequately from aggravating activities (e.g. excessive walking or standing) or those who do not perform appropriate rehabilitation exercises may also prolong their recovery.

A knee prosthesis typically lasts 20 years or longer although excessive wear and tear may reduce prosthesis longevity. It is important to maintain a healthy body weight as obesity may reduce the life span of a knee replacement.


Physiotherapy following a knee replacement

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Potential complications following a knee replacement

Although mostly uncommon, some of the potential complications of knee replacement surgery may include:

  • Temporary or permanent numbness around the incision
  • Wound infection
  • Lung infection
  • Deep vein thrombosis
  • Allergic reaction to the anaesthetic
  • Joint dislocation
  • Failure of the prosthesis (breaking or loosening)
  • Damage to blood vessels in the leg
  • Amputation of the leg due to severe wound infection or blood vessel damage
  • Paralysis of the foot due to nerve damage
  • Pulmonary emboli
  • Heart Attack
  • Stroke
  • Death

Please note that most of these complications are extremely uncommon and very rarely encountered in Physiotherapy clinical practise. One exception being temporary or permanent numbness around the incision which typically affects the majority of patients.


Other intervention following a knee replacement

Despite appropriate physiotherapy management, some patients fail to improve adequately following surgery. When this occurs the treating physiotherapist, doctor or orthopaedic surgeon can advise on the best course of management. This may include further investigations, pharmaceutical intervention, manipulation under anaesthetic (to improve range of motion) or in rare cases, further surgery.


Exercises following a knee replacement

The following exercises are commonly prescribed to patients following a knee replacement. These can usually commence once the orthopaedic surgeon or physiotherapist have indicated it is safe to do so. You should discuss the suitability of these exercises with your physiotherapist prior to beginning them. Generally, they should be performed 3 – 4 times daily and only provided they do not cause or increase symptoms.

Your physiotherapist can advise when it is appropriate to begin the initial exercises and eventually progress to the intermediate, advanced and other exercises. As a general rule, addition of exercises should take place provided there is no increase in symptoms.


Initial Exercises

Knee Bend to Straighten

Bend and straighten your knee as far as possible and comfortable without increasing your pain (figure 2). Aim for no more than a mild to moderate stretch in each direction. Repeat 10 – 20 times provided there is no increase in symptoms.

Exercises Following a Knee Replacement - Knee Bend to Straighten

Figure 2 – Knee Bend to Straighten (right leg)

Static Quadriceps Contraction

Tighten the muscle at the front of your thigh (quadriceps) by pushing your knee down into a small towel (figure 3). Put your fingers on your inner quadriceps to feel the muscle tighten during contraction. Hold for 5 seconds and repeat 10 times as hard as possible and comfortable without increasing your symptoms.

Exercises Following a Knee Replacement - Static Quadriceps Contraction

Figure 3 – Static quadriceps contraction (left leg)

Quads over Fulcrum

Begin this exercise lying on your back with a rolled towel or foam roller under your knee and your knee relaxed. Slowly straighten your knee as far as possible tightening the front of your thigh (quadriceps) (figure 4). Hold for 5 seconds and repeat 10 times as hard as possible without increasing your symptoms.

Exercises Following a Knee Replacement - Quads over Fulcrum

Figure 4 – Quads over fulcrum (left leg)


More Initial Exercises

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Intermediate Exercises

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Advanced Exercises

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Other Exercises

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Rehabilitation Protocol following a knee replacement

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Physiotherapy Products following a Knee ReplacementPhysiotherapy products following a knee replacement

Some of the most commonly recommended products by physiotherapists to hasten healing and speed recovery in patients who have had a knee replacement include:

    1. Crutches, Walking Frames or Walking Sticks
    2. Ice Packs or Hot Packs
    3. Compression Bandages
    4. Foam Rollers (for self massage)
    5. Spikey Massage Balls (for self massage)
    6. Resistance Band (for strengthening exercises)
    7. Swiss Balls (for strengthening exercises)
    8. Protective Tape
    9. Orthotics

To purchase physiotherapy products following a knee replacement click on one of the above links or visit the PhysioAdvisor Shop.


More Exercises following a Knee Replacement More exercises following a knee replacement


Useful Links following a knee replacement Useful links following a knee replacement


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