In medical terms, OA stands for osteoarthritis, the most common form of arthritis. It’s a condition where the tissues inside a joint gradually break down, causing pain, stiffness, and reduced mobility. About 528 million people worldwide were living with osteoarthritis as of 2019, a 113% increase since 1990.
What Happens Inside the Joint
Osteoarthritis is often described as “wear and tear” arthritis, but the reality is more complex than simple mechanical wearing down. The disease can damage every structure in a joint: the cartilage that cushions the ends of bones, the tendons and ligaments that hold the joint together, the thin lining inside the joint (called the synovium), and even the bone itself.
The process starts with the breakdown of cartilage, your joint’s built-in shock absorber. Enzymes inside the joint begin chewing through the two main structural proteins that give cartilage its strength and flexibility. One group of enzymes breaks down collagen, the fibers that give cartilage its tensile strength. Another breaks down proteoglycans, the molecules that help cartilage absorb compression. Once collagen is destroyed, the damage is irreversible.
As cartilage fragments float into the joint fluid, the joint lining absorbs them and responds with inflammation. This inflammation produces more destructive enzymes and inflammatory signals, creating a cycle that accelerates the damage. Meanwhile, the bone underneath the cartilage begins to thicken and form bony spurs called osteophytes. Research suggests these bone changes aren’t just a consequence of cartilage loss but may actively contribute to the disease’s progression through chemical signaling between bone and cartilage.
Joints Most Commonly Affected
OA most frequently develops in the knees, hips, hands, and spine. In the knee, it can also damage the meniscus, the rubbery disc that acts as an extra cushion between the shinbone and thighbone. The specific joints affected often reflect a combination of genetics, past injuries, and the mechanical loads those joints have carried over a lifetime.
Who Gets Osteoarthritis
About 73% of people living with osteoarthritis are older than 55, making age the strongest risk factor. But OA is not an inevitable part of aging. Joint injuries from sports or accidents, excess body weight, and repetitive occupational stress all increase your risk. Women develop OA more frequently than men, particularly after menopause. Genetics also play a role: if your parents had OA, your chances are higher.
Symptoms and How They Feel
Pain and stiffness are the hallmark symptoms. The pain typically worsens with activity and improves with rest, though in more advanced cases it can persist even when you’re sitting still. Joints may feel stiff after periods of inactivity, particularly first thing in the morning.
One useful distinction: morning stiffness from OA typically lasts 30 minutes or less. If there’s significant inflammation in the joint, it can last longer. In contrast, rheumatoid arthritis (a different condition driven by the immune system) tends to cause morning stiffness lasting an hour or more. That difference is one of the clues doctors use to tell the two apart.
Other common signs include a grating or crunching sensation when moving the joint, reduced range of motion, and visible swelling. Over time, the joint may become visibly enlarged or misaligned, particularly in the fingers and knees.
First-Line Treatments
Current guidelines from the American College of Rheumatology recommend exercise, tai chi, and self-management programs as first-line treatments for OA. This surprises many people who assume medication comes first, but the evidence is clear: regular physical activity improves both pain and function. Exercise benefits last for up to a year, while tai chi shows lasting improvement for at least 24 weeks.
Weight loss is one of the most effective interventions for knee and hip OA. Even a 5% reduction in body weight provides notable improvement in pain. For someone weighing 200 pounds, that’s just 10 pounds. Cognitive behavioral therapy, balance training, and goal-setting strategies also show consistent, measurable benefits for pain and function.
Supportive devices help with specific joints. Knee braces designed for the inner or outer compartment of the knee reduce pain and improve walking speed. Hand splints improve both pain and function for arthritis at the base of the thumb. One thing that doesn’t work: transcutaneous electrical nerve stimulation (TENS) units have not been shown to improve pain or function in knee OA, despite their popularity.
Pain Medications
When lifestyle changes aren’t enough, anti-inflammatory medications are the most common next step. Over-the-counter options like ibuprofen and naproxen reduce both pain and inflammation. Acetaminophen can help with pain but doesn’t address inflammation. Topical anti-inflammatory creams applied directly to the joint are another option, with fewer side effects than oral medications since less of the drug enters your bloodstream.
For flare-ups, doctors sometimes inject corticosteroids directly into the affected joint. These can provide relief for weeks to months but aren’t a long-term solution, as repeated injections may accelerate cartilage loss.
When Surgery Becomes Necessary
Joint replacement is considered when conservative treatments are no longer controlling pain and the cartilage is essentially gone. It’s not a decision made based on imaging alone. Two people with identical X-rays can have very different levels of pain and disability, so the decision depends heavily on how much the disease is affecting your daily life.
In earlier stages, joint-preserving surgeries can sometimes alter the course of the disease by correcting alignment or repairing damaged structures. But once the cartilage has been completely destroyed and nonsurgical treatments stop working, total joint replacement (most commonly of the hip or knee) is one of the most successful procedures in modern medicine. Most people experience dramatic pain relief and return to activities they had given up.
OA vs. Other Types of Arthritis
Osteoarthritis is fundamentally different from inflammatory types of arthritis like rheumatoid arthritis or psoriatic arthritis. Those conditions are autoimmune diseases where the immune system attacks healthy joint tissue. OA involves mechanical and biochemical breakdown of joint structures, though inflammation plays a secondary role. The distinction matters because the treatments differ significantly: autoimmune arthritis requires medications that suppress the immune system, while OA management centers on physical activity, weight management, pain control, and eventually surgery when needed.