Arthritis is an inflammation in one or more joints. It usually causes pain, stiffness and swelling. It is more common in older adults, but it can also affect younger adults and even children. Many types of arthritis exist including the following: osteoarthritis, rheumatoid arthritis, post-traumatic arthritis, septic arthritis, psoriatic arthritis, gouty arthritis, Lyme disease arthritis, spondylitic arthritis, lupus arthritis, and juvenile arthritis. Osteoarthritis is the most common type in older adults. It often affects the knee joints. Osteoarthritis happens when the protective cartilage in the joints wears away over time. Non-operative treatments like injections should always be tried first. If non-operative treatments do not work, the ultimate solution is a knee replacement (also known as a total knee arthroplasty). These surgeries offer excellent results for adults dealing with knee osteoarthritis.