Knee replacement surgery also called knee arthroplasty involves removal of damaged or diseased tissues and bone ends from the knee joint and replacing it with metal and plastic prosthetics.

Knee arthroplasty is performed in patients with severe reduction of knee mobility and pain that is uncontrolled by any medication and that persists even when at rest. (1)

The knee joint

A normal knee joint is like a hinge between the thigh bone (femur) above and shin bone or tibia below.

A small part of the joint is between the kneecap (patella) and the femur.

For easy movement between the fist-like lower ends of the femur, the button like knee cap and the plate like upper end of the tibia there is a tough tissue called articular cartilage that covers the ends of the bones within the knee joint.

This cartilage protects the ends of the bones and allows smooth movements of the joint. There is presence of a synovial membrane which covers all the surfaces within the joint.

It produces synovial fluid, which lubricates the joint and eases movement. (1)

Reasons for knee arthroplasty

Knee replacement is performed for a number of reasons, these include osteoarthritis and other types of arthritis. (1-4)

Osteoarthritis

The most common reason for knee replacement surgery is osteoarthritis.

Osteoarthritis causes damage to the articular cartilage through natural wear and tear.

There is damage to the articular cartilage due to disease or injury. This increases friction between the ends of the bones leading to pain and difficulty in movement.

With progress of the condition the bones grow thicker and produce bony outgrowths to repair the damage. This leads to further pain and joint stiffness.

Osteoarthritis may be primary affecting persons aged as young as 40. This is usually an inherited condition.

Secondary osteoarthritis usually occurs after injuries to the knee, infections of the joint, instability or fractures of the bones in the joint.

Other types of arthritis

Other reasons for joint damage who may benefit from knee arthroplasty includes those with Rheumatoid or other arthritis.

These conditions have other manifestations and effects that need to be managed as well as replacement of the joint to improve outcome.

Patients on steroids for a long time may develop special form of joint damage called avascular necrosis. These patients may also benefit from joint replacement surgeries.

Those with bleeding and coagulation disorders like haemophilia or with gout may benefit from joint replacement if there is extensive joint damage.

Bone cancers and bone tumors affecting the knee joint may also be treated with other modalities of therapy and knee replacement may be provided for better movement of the joint after surgery.

Not all patients opt for knee replacement

Not all patients with severe osteoarthritis or joint damage opt for knee replacement surgery.

Those who would benefit from a knee arthroplasty include (2):

• Patients with severe knee pain that limits everyday activities including walking, using the stairs, or even getting in and out of chairs
• Patients needing a walking aid for walking even a short distance. Walking may lead to significant pain
• Moderate to severe pain even when resting either day or night
• Knee swelling, pain and inflammation (redness, warmth and tenderness) for a long time that does not improve with rest or medication
• Patients with a deformity of the knee joint
• Severe stiffness of the knee leading to inability to bend and straighten the joint