Understanding Knee Replacement

Knee arthritis, which can be caused by degeneration, inflammation, and infection commonly presents with swelling, pain and feeling of warmth in the joint.

Knee osteoarthritis is a condition that the cartilage inside the knee joint is constantly worn away throughout the years. Other components including the muscles, ligaments, and bone around the knee will also be affected.

Injury, inflammatory disease like rheumatoid arthritis and gout, and knee joint infection can damage any intra-articular structure leading to knee arthritis and secondary degeneration.

Osteoarthritis of the knee is divided into four stages. Stage 4 is considered as severe osteoarthritis and cartilage degeneration is advanced.

Knee Prosthesis

Total knee prosthesis is composed of femoral, tibial and patellar component.

Partial knee prosthesis can be used to replace the damaged inner or outer compartment of knee joint. It is composed of femoral and tibial implants. When the damage is confined to the patello-femoral joint, it can be replaced with the one with patellar and femoral implants.

For an artificial joint, the femoral implant is made of alloy metal, e.g. cobalt-chromium alloy. The tibial implant is made of polyethylene, which is commonly known as plastic, with a metal alloy base. The patellar implant is made of polyethylene. With this combination, the wear rate is relatively low and hence the artificial joint becomes more durable. Besides, cement is also commonly used for stabilizing the artificial joint.

Operation Procedure

1. A vertical incision is made over the front of knee joint.
2. Excessive synovium or bony spur is removed.
3. The distal end of femur is cut to fit the femoral implant.
4. The proximal end of tibia is cut to fit the tibial implant.
5. The femoral and tibial metal implants are fixed with cement or non-cement method. Tibial plastic is inserted. The alignment, stability and mobility of the knee joint are examined.
6. If there is clinical need, the surgeon will cut the back side of patella and then fix the patella plastic implant with cement.
7. A drainage tube may be placed near the wound, and wound is closed.
8. The operative site is dressed with bandage.

General Complications

• Wound infection
• Post-operative chest infection
• Myocardial infarction
• Stroke

Surgical Risks and Complications

• Bleeding
• Nerve and vessels injury
• Prosthetic joint infection
• Deep vein thrombosis and pulmonary embolism
• Joint stiffness
• Joint dislocation