The Two Main Causes of Arthritis

Osteoarthritis happens when the cartilage that cushions your joints wears down over time. This is the most common type — it accounts for about 80 percent of arthritis cases. The cartilage breaks down gradually, usually over years, until bone rubs directly on bone. It most often affects knees, hips, hands, and the spine.

Rheumatoid arthritis is different. Your immune system attacks the lining of your joints by mistake, causing inflammation and pain. This can happen suddenly and affect multiple joints at once. It is less common than osteoarthritis but often more severe, and it can damage joints permanently if left untreated.

There are also rarer types — gout (caused by uric acid crystals in joints), lupus, psoriatic arthritis, and others — but osteoarthritis and rheumatoid arthritis account for the vast majority of cases.

Key Takeaways

  • Osteoarthritis develops when joint cartilage wears away over time, usually from age, injury, or repeated stress on a joint.
  • Rheumatoid arthritis happens when your immune system attacks joint linings, and it can develop at any age, including childhood.
  • Age, family history, previous joint injury, and excess weight all raise your risk of developing osteoarthritis.
  • Women are more likely to develop rheumatoid arthritis than men, and it often runs in families.
  • Some arthritis types have no known cause, but many can be slowed or managed once you understand what is driving the damage.

Age and Wear on Joints

Osteoarthritis is largely a disease of time. The longer your joints have been in use, the more likely the cartilage has worn down. Most people do not develop symptoms until after age 50, though the damage can start much earlier without causing pain.

This does not mean arthritis is inevitable. Some people reach 80 with healthy joints, while others develop it in their 40s. The difference depends on how much stress you have put on your joints, whether you have injured them, and your genes. A person who did heavy physical labor for decades is more likely to develop osteoarthritis than someone in a desk job, even if they are the same age.

Injury and Overuse

A single serious injury to a joint — a torn ligament, a fracture, or a dislocation — can set the stage for arthritis years later. The joint may heal, but the cartilage damage can continue to worsen over time. Athletes and people in physically demanding jobs face higher risk for this reason.

Repetitive stress also matters. Doing the same motion thousands of times — typing, assembly line work, throwing — can gradually damage cartilage. The damage is usually slow, but it adds up. People who have injured a joint are two to three times more likely to develop arthritis in that joint later in life.

Weight and Joint Load

Extra weight puts more pressure on weight-bearing joints like the knees, hips, and lower back. Each pound of body weight adds roughly four pounds of force to your knees when you walk. Over years, this extra load can accelerate cartilage breakdown.

Weight also affects inflammation throughout the body. Fat tissue produces inflammatory chemicals that can make rheumatoid arthritis worse. Losing weight does not reverse existing arthritis, but it can slow progression and reduce pain, especially in the knees and hips.

Family History and Genes

Arthritis runs in families. If your parents or siblings have osteoarthritis, your risk is higher. The same is true for rheumatoid arthritis — it is more common in people whose relatives have it. Genes influence how your cartilage holds up, how your immune system responds, and how much inflammation your body produces.

Having a family history does not mean you will definitely develop arthritis. It means the risk is higher, not certain. Environmental factors — injury, weight, activity level — still play a major role in whether and when arthritis appears.

Immune System and Inflammation

Rheumatoid arthritis and some other types are autoimmune diseases, meaning your body's defense system attacks its own tissues. Why this happens is not fully understood, but researchers have found that certain genes make it more likely. Infections, smoking, and hormonal changes may also trigger the immune system to start attacking joints.

Women develop rheumatoid arthritis about three times more often than men. Hormonal changes around menopause can worsen symptoms. Pregnancy sometimes improves symptoms temporarily, then they often return after delivery.

Smoking and Other Risk Factors

Smoking increases your risk of rheumatoid arthritis, even years after you quit. It also makes existing arthritis worse and slows healing. The exact mechanism is not clear, but smoking appears to trigger immune system changes that promote joint inflammation.

Other factors that raise your risk include previous infections (some infections can trigger arthritis), certain medications, and metabolic conditions like gout. Alcohol use, especially heavy drinking, is linked to gout and can worsen inflammation in other types of arthritis.

Frequently Asked Questions

Can arthritis develop suddenly, or does it always come on slowly?

Osteoarthritis usually develops gradually over years, so you may not notice symptoms until significant damage has occurred. Rheumatoid arthritis, by contrast, can appear suddenly — you might wake up with swollen, painful joints that were fine the day before. Some people develop symptoms over weeks; others over months.

If my parent has arthritis, will I definitely get it?

No. Family history raises your risk, but it does not may provide arthritis. Many people with a family history never develop it, and many without family history do. Your lifestyle choices — staying active, maintaining a healthy weight, avoiding injury — can significantly influence whether arthritis develops.

Does exercise cause osteoarthritis?

Regular moderate exercise does not cause arthritis and may actually protect your joints by keeping muscles strong and cartilage nourished. High-impact sports and repetitive stress over many years can increase risk, but normal activity and fitness do not. People who are sedentary often develop arthritis faster than those who stay active.

Can you get arthritis from cold weather?

Cold does not cause arthritis, but many people report that cold weather makes existing arthritis pain worse. This may be because cold air pressure changes affect joint fluid or because people move less in cold weather. The arthritis itself was already there — the cold just makes symptoms more noticeable.

Is there a way to prevent arthritis if it runs in my family?

You cannot prevent arthritis entirely if you are genetically predisposed, but you can reduce your risk and delay onset. Maintain a healthy weight, stay physically active, protect your joints from injury, avoid smoking, and manage any infections promptly. These steps will not may provide you avoid arthritis, but they can make a real difference in when and how severely it develops.