Knee replacement surgery is used as a treatment option for a variety of different conditions including deformity, knee injury, bone tumour and arthritis. Both rheumatoid arthritis and osteoarthritis can bring about the onset of symptoms but osteoarthritic change is much more common than rheumatoid problems.

This article on knee replacement surgery is written by Max Gibbons, Consultant Orthopaedic and Oncology Surgeon, Knee and Hip Specialist, Oxford.

Knee replacement is usually considered once other therapies including pain medications and exercise programmes have failed. Depending on the severity and location of the disease, either a total or partial knee replacement may be considered. Sometimes by the time a patient sees a consultant specialist however the degenerative changes are too severe to address the condition using conservative methods.

The symptoms

The symptoms of osteoarthritis of the knee can present at different times depending on the activities a person is carrying out at any given time. The description of the symptoms in the most general sense is that a person will experience knee pain or loss of flexibility. This pain often presents as follows:

  • Pain resulting in loss of sleep at night
  • Slight or no relief of pain when taking medications
  • Problems going up and down flights of stairs
  • Chronic stiffness and or swelling in the knee
  • Being unable to participate in leisure activities due to knee pain

When these kind of symptoms become limiting on mobility and activities of daily living primary care practitioners (or General Practitioners) will make a referral to an orthopaedic specialist. The specialist, a consultant knee surgeon, will examine the knee, its movement and the strength of the muscles around the joint. An x-ray will be necessary to show the surgeon the extent of the osteoarthritic change and an MRI scan may be necessary.

When the arthritic changes occur to this extent it would indicate that a total knee replacement is required rather than a partial knee replacement, which is suitable only when single-compartment osteoarthritis is present.

The Patellofemoral compartment is the part of the joint beneath the patella (or kneecap) itself. 

The two condyles, as they are called, extend down from the femur and are called the medial (in-side) and the lateral (outside) condyles. The medial condyle is on the left hand side and the lateral on the right hand side. The simple way to remember this is that the lateral compartment is above the fibula, the smaller bone in the lower leg. The large bone in the lower part of the leg is called the tibia on which the two condyles bear. Arthritic change and the inflammation it causes increases friction in the knee joint, wears away cartilage and is the primary cause of the symptoms leading to knee replacement.

Treatment - surgery for total knee replacement

Before a patient is admitted for knee replacement they will be asked to make a visit for a pre-operative assessment. This is a thorough examination and education process during which routine tests are carried out. It is a very good opportunity for patients or their relatives to ask any questions to address their concerns about the upcoming operation and preparing for it.

The knee replacement operation itself at the most basic level involves removing the arthritic bone and tissue and covering the medial and lateral condyle and the top of the tibia with new bearing surfaces.  The operation normally takes around two hours and is performed under anaesthetic. It is possible to use either regional or general anaesthetic, the latter being used in most instances.

During surgery, a midline incision is made over the patella which is moved aside along with muscles and connective tissues. The operation is carried out with the knee in a bent position allowing all parts of the joint to be exposed. Arthritic bone is removed from both the tibia and femur, preserving as much healthy bone and tissue as possible. The tibia is hollowed out enough for the tibial implant to be inserted in a stable position and once the femoral and tibial compartments are smoothed over the surgeon will carefully measure both for the prostheses (implants).

Once measured, a precise amount of bone will be removed from each part of the knee joint to ensure a good fit with the prostheses in place. Once the implants are inserted, which can be done with or without cement, the surgeon will bend and rotate the knee to confirm that it moves properly and the implants are aligned.

After surgery

A patient will normally stay in hospital for three to four days following a total knee replacement. With minimally invasive advances in surgical techniques, it can be possible to start to walk short distances with the aid of crutches or a walker only hours after surgery. Nurses and physiotherapists will spend the most time with each patient and determine the most appropriate mobilisation programme tailored to each individual.

The exercises learned while in hospital will be a very important part of the long-term success of the knee replacement and should be continued as a part of a daily routine as prescribed by the physiotherapists while in hospital.

Normally a patient will be asked to attend a follow-up appointment six to eight weeks after leaving hospital to see their consultant surgeon who will review progress and, if appropriate, make recommendations or adjustments to a patient’s activities at that time.

Partial knee replacement

Partial knee replacement is intended for use in individuals with osteoarthritis limited to either the medial or lateral compartment (side) of the knee. Partial knee replacement involves removing the diseased cartilage and a small amount of bone in one compartment of the joint and resurfacing it with orthopaedic implants.

The Operation

During surgery, the joint is exposed by an incision made at the front of the knee slightly off-centre. This is a smaller incision than a total knee replacement so recovery and the length of stay in hospital is much shorter.

The damaged bone ends are then resurfaced with components designed to re-create the natural contours of the bones in a healthy knee. The metal and polyethylene (high durability plastic) implants allow the bones to smoothly glide against each other much like natural cartilage. The operation of partial knee replacement is performed while under general anaesthetic. The surgery itself will last approximately one to one and a half hours. Care for patients before surgery and time spent in the recovery room can add an additional hour or two before returning to the hospital room.

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