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Knee 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). Between the bone ends are two round discs made of cartilage called the medial (inner) and lateral (outer) meniscus. 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. In addition, strong ligaments and connective tissue hold the bones of the knee together, giving it stability.
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 the use of 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 anesthetic or occasionally spinal anesthetic 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 5 – 5 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 physical therapy 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 tumors

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 such as 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 and 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 usually the case in younger patients who have had excellent strength and flexibility of the knee prior to surgery, have appropriate medication and are adhering to appropriate rehabilitation under physiotherapy guidance.
  • 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 hills or on uneven surfaces or standing still for prolonged periods), with excessive bending, straightening or twisting of the knee, when climbing stairs, attempting to kneel or when squatting. 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 and 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, pins and needles or numbness may also be experienced which will vary in severity from patient to patient.

Treatment following a knee replacement
Directly following knee replacement surgery the knee is usually covered with a dressing and a drainage tube is used to remove excess fluid from the wound. Antibiotics and blood thinning medication are usually given to reduce the risk of infection and blood clot formation. Strong pain relief is administered often via an epidural or drip. Early exercises to move the feet and other leg are encouraged as soon as possible, along with the use of compressive TED stockings, to reduce the risk of clot formation. Patients are usually encouraged to sit out of bed on the first day after surgery (with assistance from the physical therapist) and to walk around on the second day after surgery with the assistance of crutches or a walking frame, and, under physiotherapy guidance. The treating physical therapist will advise how to perform appropriate knee exercises. The use of a continuous passive motion machine may also be advised by some surgeons. Stitches may be dissolvable or are usually removed approximately 10 days after surgery.
  • Following knee replacement surgery and discharge from hospital, most patients heal well with appropriate physical therapy. The success rate of treatment is largely dictated by patient compliance. Crutches are usually required for days to weeks as guided by the surgeon and treating physical therapist. Activities which place large amounts of stress through the knee should be avoided particularly excessive twisting and weight bearing activities (such as prolonged standing or walking, lifting, squatting, jumping, kneeling and running etc). Avoiding aggravating activities allows the healing process to take place in the absence of further damage.
  • Following a knee replacement, patients usually benefit from following RICE. RICE is beneficial in the first 72 hours following surgery or when inflammatory signs are present (i.e. morning pain, pain with rest, or new swelling). This involves resting from aggravating activities, regular icing, the use of a compression bandage and keeping the leg elevated. Anti-inflammatory medication may also significantly hasten the healing process by reducing the pain and swelling associated with inflammation.
  • Patients who have undergone a knee replacement should perform regular flexibility and strengthening exercises as part of their rehabilitation to ensure an optimal outcome. Emphasis is placed on restoring full knee extension and flexion range of movement and quadriceps strength. Hamstring, gluteal and calf strengthening exercises are also important to improve the control of the knee joint with weight-bearing activities. Hydrotherapy exercises or stationary bike are also often indicated to improve movement and strengthen the knee in a low weight bearing environment. The treating physical therapist can advise which exercises are most appropriate for the patient and when they should be commenced.
  • Manual "Hands-on" Therapy from the treating therapist such as massage, joint mobilization, dry needling and electrotherapy are important to improve scar tissue flexibility and range of movement. This is particularly important in the first 6 – 12 weeks.
  • Review with an occupational therapist may be indicated to teach strategies to improve function and mobility around the home this may include the use of appropriate aids, high chairs, rails etc.
  • In the final stages of rehabilitation, a gradual return to activity can occur as guided by the treating physical therapist provided there is no increase in symptoms.

Prognosis following a knee replacement
Approximately 90% of patients who have a knee replacement experience less pain and improved mobility compared to preoperatively. Recovery times vary significantly from patient to patient although 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.
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, rehabilitation may require an extended period. Following surgery, patients who do not rest adequately from aggravating activities (e.g. excessive walking or standing) or those who do not perform exercises appropriately may also prolong their recovery.
A knee prosthesis typically lasts approximately 10 years although excessive wear and tear may reduce prosthesis longevity. It is particularly important to maintain a healthy weight as obesity may reduce the life span of a knee replacement.

Physical therapy following a knee replacement
Physical therapy treatment is vital to hasten the healing process and ensure an optimal outcome in all patients following a knee replacement. This should ideally begin prior to surgery. Treatment may comprise:
  • Soft tissue massage
  • Electrotherapy
  • The use of crutches
  • The use of a compression support
  • Joint mobilization
  • Dry needling
  • Hydrotherapy
  • Ice or heat treatment
  • Progressive exercises to improve flexibility, strength (especially the quadriceps muscle) and balance
  • Activity modification advice
  • Education
  • Biomechanical correction
  • Anti-inflammatory advice
  • Weight loss advice where appropriate
  • A gradual return to activity program

Potential complications following a knee replacement
Some of the potential complications of knee replacement surgery may include:
  • Wound Infection
  • Allergic reaction to the anesthetic
  • 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
  • Temporary or permanent numbness around the incision
  • Paralysis of the foot due to nerve damage
  • Lung infection
  • Deep vein thrombosis
  • Heart Attack
  • Stroke
  • Death

Other intervention following a knee replacement
Despite appropriate physical therapy management, some patients fail to improve adequately following surgery. When this occurs the treating physical therapist, doctor or orthopedic surgeon can advise on the best course of management. This may include further investigations, pharmaceutical intervention, or further surgery.