Definition and Overview

The knee is the largest joint in the human body. Its trocho-ginglymus structure allows for extension, flexion, and slight rotation both internally and externally. However, the knee is particularly vulnerable to problems such as acute injury and osteoarthritis as its cartilage can be broken down by numerous factors and medical conditions including obesity and issues in muscle strength.

A total knee replacement surgery, or total knee arthroplasty, is often recommended for patients suffering from disabling pain brought about by a variety of conditions affecting the knee and surrounding structures. This surgery is not the first line of treatment and is only considered when the patient’s condition is not responding to more conservative forms of treatment, such as medication or physical therapy.

The surgery involves the removal of the diseased knee joint, which is then replaced with a stronger, sturdier artificial material that can perform the same functions. Common artificial knee joints installed in patients are made of biocompatible metal and plastic components, which allow the continued motions of the joint. The procedure is followed by months of physical therapy to help restore mobility the patient enjoyed before the operation or the condition that necessitated the procedure.

Who Should Undergo and Expected Results

People with the following conditions are often considered as ideal patients for a total knee replacement surgery:

  • Advanced osteoarthritis - This joint disease is a result of the breakdown of the cartilage in the joints and the underlying bone. Patients experience stiffness and pain in the major joints, including the knee. Over time, the swelling of the joint, the significant decrease in range of motion, and muscle loss significantly restrict movements and result in constant pain.

  • Progressive rheumatoid arthritis - Patients experiencing longer-lasting, more intense flares, diagnosed with the disease at a young age, with active inflammation in blood and joint fluid tests, suffering from extensive joint damage as confirmed by x-ray results, and have significant rheumatoid factor or citrulline antibody levels are highly recommended to undergo the surgery.

  • Varus and valgus deformities - Patients with an inward or outward angulation of the knee joint’s distal segment can undergo the procedure to correct the deformity.

  • Joint or bone trauma. The surgery can be recommended to patients—especially younger ones—suffering from the effects of significant trauma to the joints or bone of the knee.

How is the Procedure performed?

A total knee replacement procedure is generally performed with the following steps:

  • Choosing prosthesis to replace the knee joint is usually done before the patient and the medical team start preparing for the procedure. The doctor will discuss the benefits of each option to help the patient make a well-informed choice. Options include a fixed bearing, a PCL (posterior cruciate ligament)-bearing, PCL-substituting, medial pivot, and rotating platform and mobile bearing.

  • The patient can be placed either under regional or general anaesthesia. Research shows that patients who have had epidural anaesthesia are less likely to develop deep vein thrombosis after the procedure.

  • The patient will then undergo a three-step evaluation (medical evaluation, a series of laboratory studies, and several imaging tests such as MRI and CT scan) so surgeons can carefully plan the operation and assess possible risks and complications.

  • During the procedure, the surgeon will make an incision around the knee joint. Cuts will also be made in the bone and ligaments to lift the joint out of its position.

  • The prosthesis will be placed on the knee joint area, and will be cemented in place using polymethyl methacrylate cement. The incisions will then be stitched up.

  • Foot pulses will be checked after the procedure.

  • CPM or continuous passive motion machines and exercises will be used to facilitate knee movement several days after the surgery.

  • Physical therapy will be recommended to improve patient’s mobility and this can last for several months.

Possible Risks and Complications

Joint replacements procedures are particularly risky, which is why they are not offered as the first line of treatment and are only prescribed when other conservative methods have been exhausted.

Possible risks and complications of total knee replacement surgery include:

  • Joint infection - Also known as bacterial or septic arthritis, this condition is the most serious complication that can result from any joint replacement surgery. Bacteria can enter the joint during the procedure, which can cause rapid deterioration of the cartilage in the knee, as well as bone damage. Symptoms of this condition include significant pain in the knee, redness, swelling, and loss of movement.

  • Deep vein thrombosis - This condition involves blood clot formation in the deep veins of the legs. Patients may experience redness, enlarged and engorged superficial veins, swelling, and pain in the legs after the procedure. To prevent this complication, patients can elevate the legs periodically, perform circulation-improving lower leg exercises, wear support stockings, and take blood-thinning medications.

  • Periprosthetic fractures, especially in older patients

  • Loss of motion
  • Instability

    References:

  • Memtsoudis SG, Sun X, Chiu YL, Stundner O, Liu SS, Banerjee S, et al. Perioperative comparative effectiveness of anesthetic technique in orthopedic patients. Anesthesiology. 2013 May. 118(5):1046-58.

  • A multicenter, randomized, triple-masked, placebo-controlled trial of the effect of ambulatory continuous femoral nerve blocks on discharge-readiness following total knee arthroplasty in patients on general orthopaedic wards. Pain. 2010 Sep. 150(3):477-84.

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