What causes arthritis to develop

Arthritis happens when the protective cartilage inside your joints wears down or your immune system attacks the joint lining. There is no single cause — arthritis develops differently depending on the type. Osteoarthritis comes from years of use and wear on your joints. Rheumatoid arthritis and other inflammatory types happen when your body's immune system mistakenly damages joint tissue. Understanding which type you have matters because the reasons behind it shape how it progresses and what helps.

Your joints are where two bones meet. Cartilage covers the ends of those bones like a cushion, letting them slide smoothly. When that cartilage breaks down or the joint lining becomes inflamed, movement becomes painful and stiff. The reason this happens varies — sometimes it is age and repetitive motion, sometimes it is your genetics, sometimes it is your immune system, and often it is a combination.

Key Takeaways

  • Osteoarthritis develops when cartilage wears down over time from use, age, or injury to a joint.
  • Rheumatoid arthritis and lupus happen when your immune system attacks the lining of your joints, not from wear and tear.
  • Risk factors include age, family history, previous joint injuries, excess weight, and certain occupations that stress specific joints.
  • Gout develops when uric acid crystals build up in joints, usually triggered by diet, dehydration, or certain medications.

Osteoarthritis: wear and tear on joints

Osteoarthritis is the most common type of arthritis. It develops when the cartilage that cushions your joints gradually breaks down over time. This usually happens slowly — over years or decades — as you use your joints for everyday activities like walking, gripping, and bending. The cartilage cannot repair itself as quickly as it wears away, so the damage builds up.

Several things speed up this wear and tear. Age is one: cartilage becomes thinner and less flexible as you get older, usually starting around age 50 or later. A previous injury to a joint — a broken bone, a torn ligament, or a bad sprain — can trigger osteoarthritis in that joint years afterward, even if the injury healed. Excess weight puts extra stress on weight-bearing joints like your knees, hips, and lower back. Repetitive motions from your job or hobbies can wear down specific joints: a baker's hands, a runner's knees, a carpenter's shoulders.

Genetics also play a role. If your parents or grandparents had osteoarthritis, you are more likely to develop it. This does not mean you will definitely get it, but your joints may be more prone to cartilage breakdown.

Rheumatoid arthritis: when your immune system attacks joints

Rheumatoid arthritis (RA) is different from osteoarthritis because it is not caused by wear and tear. Instead, your immune system mistakenly attacks the synovium — the lining of your joints. This causes inflammation, swelling, pain, and eventually damage to the cartilage and bone underneath. RA can develop at any age, though it is most common in people over 40.

The exact reason your immune system turns against your joints is not fully understood, but researchers know that genetics and environmental triggers both matter. If you carry certain genes — particularly one called HLA-DR4 — your risk is higher. Environmental factors like smoking, infections, or stress may trigger the immune attack in people who are genetically prone. RA often develops suddenly and affects multiple joints at once, usually on both sides of your body (both hands, both knees).

Unlike osteoarthritis, which develops slowly in one or two joints, RA can be aggressive and spread quickly. It also causes fatigue and sometimes fever because it is a whole-body inflammatory condition, not just a joint problem.

Other types of arthritis and their causes

Several other forms of arthritis have different causes. Gout develops when uric acid crystals build up inside a joint, usually the big toe. This happens when your body produces too much uric acid or cannot get rid of it fast enough. Diet plays a role — foods high in purines (red meat, organ meats, certain seafood, alcohol) raise uric acid levels. Dehydration and certain medications like diuretics can also trigger gout attacks.

Lupus and psoriatic arthritis are autoimmune conditions similar to RA: your immune system attacks joint tissue. Lupus is a systemic disease that affects skin, kidneys, and other organs in addition to joints. Psoriatic arthritis develops in people who have psoriasis (a skin condition) and causes joint inflammation.

Infectious arthritis happens when bacteria, viruses, or fungi enter a joint and cause inflammation. This can follow an injury, surgery, or infection elsewhere in your body. Ankylosing spondylitis primarily affects the spine and develops in people who carry a specific gene (HLA-B27), though carrying the gene does not may provide you will develop the condition.

Risk factors that make arthritis more likely

Some people develop arthritis and others do not, even with similar lifestyles. Risk factors tilt the odds. Age is the strongest risk factor for osteoarthritis — your cartilage straightforward has more time to wear down. Sex matters too: women are more likely to develop rheumatoid arthritis and lupus, while men are more likely to develop gout.

Family history increases your risk for most types of arthritis because genes influence how your joints age and how your immune system behaves. Previous injuries to a joint make that joint vulnerable to arthritis later, even decades later. Excess weight stresses your knees, hips, and lower back, accelerating cartilage breakdown. Smoking increases the risk of rheumatoid arthritis and may worsen inflammation. Occupational stress — jobs that require repetitive gripping, kneeling, or heavy lifting — can trigger osteoarthritis in those specific joints.

Having one risk factor does not mean you will develop arthritis. Many people with family history never develop it. But the more risk factors you have, the higher your chances.

What happens inside your joint when arthritis develops

Understanding the physical changes inside your joint helps explain why arthritis causes pain and stiffness. In osteoarthritis, the cartilage surface becomes rough and thin. As it wears away, the bones underneath start to rub together. Your body tries to repair the damage by growing extra bone around the joint, creating bumps called bone spurs. These changes make movement painful and limit how far you can bend or straighten the joint.

In rheumatoid arthritis, the inflamed synovium (joint lining) swells and produces extra fluid. This swelling is why RA joints feel puffy and warm to the touch. Over time, the inflammation damages the cartilage and bone, causing permanent deformity if left untreated. The inflammation also releases chemicals that affect your whole body, which is why RA causes fatigue and sometimes fever.

In gout, uric acid crystals form needle-like shapes inside the joint. These crystals trigger an intense inflammatory response — your immune system treats them as invaders and attacks them, causing the sudden severe pain and swelling that gout is known for.

Frequently Asked Questions

Can you catch arthritis from someone else?

No. Osteoarthritis, rheumatoid arthritis, gout, and most other types of arthritis are not contagious. Infectious arthritis is caused by bacteria or viruses that enter the joint, but that is different — the infection itself is what causes the arthritis, not arthritis spreading from person to person.

Does arthritis always get worse over time?

Osteoarthritis usually progresses slowly over years, though the rate varies. Rheumatoid arthritis can be aggressive if untreated, but modern medications can slow or stop the damage. Gout attacks come and go — you may have one attack and then none for months or years. The progression depends on the type, how early treatment starts, and how well you manage it.

Can you prevent arthritis if it runs in your family?

You cannot prevent arthritis entirely if you carry the genes for it, but you can reduce your risk. Maintaining a healthy weight, staying active, protecting your joints from injury, and avoiding smoking all help slow cartilage breakdown. For rheumatoid arthritis, there is no proven prevention, but early treatment once symptoms appear can prevent joint damage.

Is arthritis only in older people?

Most people develop osteoarthritis later in life, but rheumatoid arthritis, lupus, and gout can start at any age, including childhood. Juvenile idiopathic arthritis affects children. Young people can also develop osteoarthritis after a serious joint injury.

What is the difference between arthritis pain and normal joint pain?

Arthritis pain is usually persistent — it does not go away after rest or a few days. It often feels stiff in the morning and improves slightly with movement. Normal joint pain from overuse usually improves within a few days of rest. If joint pain lasts more than a few weeks, it is worth discussing with your doctor.