The American Academy of Orthopaedic Surgeons explains that total knee replacement involves four basic steps: preparing the knee by removing damaged cartilage and a small amount of underlying bone; replacing the missing tissue with metal components to recreate the joint's surface; resurfacing the patella or kneecap with plastic in some cases; and insertion of a plastic spacer between the metal parts to allow a smooth gliding motion. Total knee replacement is recommended for patients whose pain or stiffness prevents or limits daily activities such as walking, climbing stairs, and getting in and out of chairs.
According to the American Academy of Orthopaedic Surgeons, replacement is also recommended for patients who have pain while resting or chronic inflammation that doesn't improve with rest or medication. Knee deformities, failure to respond to conservative treatments such as anti-inflammatory medications, cortisone or lubricating injections, physical therapy, and less-invasive surgery also lead to knee replacement.
Knee pain is generally caused by arthritis, including osteoarthritis, rheumatoid arthritis and post-traumatic arthritis. Most patients who undergo total knee replacement are between the ages of 50 and 80, but there is no absolute age or weight limit for surgery, according to the American Academy of Orthopaedic Surgeons. Total knee replacements have been successfully performed on patients of all ages, including young teenagers and the elderly.