Arthritis is generally due to "wear and tear." Some individuals may be more susceptible to knee arthritis than others, possibly due to their genetic makeup. Other patients may develop osteoarthritis related to a previous knee injury.

Arthritis pain in the knee is generally felt as a deep, dull ache. The knee pain is usually worse with activities such as walking. When knee arthritis pain is very advanced, running will be impossible. After increased activity, such as a long walk, knee arthritis pain will usually be more severe. Generally, knee arthritis is easily diagnosed with plain x-rays. MRI is generally not required to make this diagnosis.

Knee arthritis is treated initially with non-operative management. This includes medication, such as non steroidal anti-inflammatory drugs, as well as Tylenol. Chondroitin and glucosamine have been proven to be effective for alleviating pain related to knee arthritis. Physical therapy is a very valuable non-operative management option to improve the pain related to knee arthritis and increase function. Injections may also be useful including cortisone or visco-supplementation. A brace may help some patients with advanced knee arthritis. A cane can also be of assistance to patients with knee arthritis. If non-operative management does not sufficiently improve the symptoms, surgery may be indicated. Most commonly, total knee replacement (also known as total knee arthroplasty or TKA) is the procedure of choice. In some cases, a partial knee replacement can be performed. Knee replacement surgery involves resurfacing the ends of the bones with metal and plastic components, so that the bone on bone is eliminated; therefore the pain is reduced.

After total knee replacement surgery, patients generally stay in the hospital for three to five days. Physical therapy begins the day after surgery, and the patient gets out of bed and begins to walk. Range of motion exercises are also started on the first day after the knee replacement. Patients are usually able to walk without assistance within two weeks, and most patients can walk without a limp (or minimal limp) within two months. The recovery period following total knee replacement usually lasts between three and six months. Physical therapy is required to regain range of motion and to improve walking ability.