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Oxford University Hospitals NHS Foundation Trust
Hip and Knee

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Knee arthritis

Diagram showing how arthritis affects the knee

Osteoarthritis is the disease process by which joints wear out. As the joint surface wears away it sheds wear particles which stimulate the joint lining to produce fluid, causing the knee to swell. When the articular cartilage wears through, the underlying bone becomes exposed. The exposed bone rubs against exposed bone when walking and this causes pain - often described as a toothache type pain.

Factors contributing to the development of osteoarthritis include:

  • genetic factors
  • the alignment of the limb and distribution of load
  • body weight and activity level
  • injuries including fractures and ligament tears
  • removal of the meniscal cartilages.


Most people do not require surgery in the early stages of arthritis. Symptoms can often be improved by a combination of:

  • pain killing medication
  • simple exercises
  • keeping weight down.

We may recommend joint replacement surgery as the joint becomes more worn out with time.

Joint replacement surgery

Often one side of the knee joint wears out first. If the remaining cartilage and ligaments of the knee are in a good condition then this part of the knee can be replaced. This is called a unicompartmental knee replacement and preserves bone for any future surgery. The operation is less traumatic than a total knee replacement and allows a speedier recovery and better function in the knee.

If the pattern of wear involves more than one area, or the ligaments are not functioning normally, then a total knee replacement can be performed. This can replace all the bearing surfaces of the knee with metal and plastic (high density polyethylene) components.

For more information, please download the booklet below: