Knee Arthritis

Characteristics of knee arthritis

There are over 100 types of arthritis, and all of them can affect the knee, and the knee is the most-commonly affected joint. Most patients who have arthritis are over age 50, but certain types and patterns of arthritis can affect younger patients. Arthritis of the knee causes pain, stiffness, and sometimes swelling. Patients with more advanced arthritis find that even simple daily activities like walking, arising from a chair, and performing self-care can be affected. Most patients with arthritis can achieve some measure of relief from activity modifications, pills, or joint injections; however, for some patients these remedies are insufficient to provide a satisfactory quality of life. These patients sometimes consider knee replacement surgery. More details about the common characteristics of knee arthritis follow below:


Pain is the most noticeable symptom of knee arthritis. In most patients, the pain gradually gets worse over time, but sometimes has more sudden “flares” where the symptoms get acutely severe. The pain is almost always worsened by weight-bearing and activity. In some patients, the pain becomes severe enough to limit even routine daily activities.


Morning stiffness is present in certain types of arthritis; patients with this symptom may notice some improvement in knee flexibility over the course of the day. For information about other kinds of arthritis, see our articles on knee arthritis.

Swelling and warmth

Patients with arthritis sometimes will notice these symptoms. If the swelling and warmth are excessive, and are associated with severe pain, inability to bend the knee, and difficulty with weight-bearing, those signs might represent an infection. Such severe symptoms require immediate medical attention


The knee joint has three “compartments” that can be involved with arthritis. Most patients have both symptoms and findings on X-rays that suggest involvement of two or more of these compartments. Patients who have arthritis in two or all three compartments, and who decide to get surgery, most often will undergo total knee replacement.

However, some patients have arthritis limited to one compartment of the knee–most commonly the medial side. When patients with one-compartment arthritis (also called “unicompartmental” arthritis) decide to get surgery, they may be candidates for minimally-invasive partial knee replacement (mini knee)

Types of Arthritis

Inflammatory arthritis

This broad category includes a wide variety of diagnoses, including Rheumatoid arthritis, lupus, gout, and many others. It is important that patients with these conditions be followed by a qualified rheumatologist, as there are a number of exciting new treatments that may decrease the symptoms and perhaps even slow the progression of the joint damage.

Patients with inflammatory arthritis of the knee usually have joint damage in all three compartments, and therefore are not good candidates for partial knee replacement. However, inflammatory arthritis patients who decide to have total knee replacement have an extremely high likelihood of success; these patients often experience total or near-total pain relief following a well-performed joint replacement.


Osteoarthritis is also called OA or “degenerative joint disease.” OA patients represent the large majority of arthritis sufferers. OA may affect multiple joints, or it may be localized to the involved knee. Activity limitations due to pain are the hallmarks of this disease.

OA patients who have symptoms limited to one compartment of the knee sometimes are good candidates for minimally-invasive partial knee replacement (mini knee).

Similar conditions

Meniscus tear

Sometimes patients with knee pain don’t have arthritis at all. Each knee has two rings of cartilage called “menisci” (this is the plural form of “meniscus”#. The menisci work similarly to shock absorbers in a car.

Menisci may be torn acutely, in a fall or as the result of other trauma, or they may develop degenerative tears from wear-and-tear over many years. Patients with meniscus tears experience pain along the inside or outside of the knee. The pain is worse with deep squatting or twisting. Popping and locking of the knee are also occasional symptoms of meniscus tears. Since some of these symptoms may be present with arthritis, and the treatment of arthritis is different from that of meniscus tears, it is important to make the correct diagnosis. A good orthopedic surgeon can distinguish the two conditions by taking a thorough history, performing a careful physical examination, and by obtaining imaging tests.