How arthritis develops depends on which type you have

Arthritis is not a single disease with one cause. The two most common types — osteoarthritis and rheumatoid arthritis — develop through completely different processes in your body. Osteoarthritis happens when the protective cartilage in your joints wears down over time. Rheumatoid arthritis happens when your immune system mistakenly attacks the lining of your joints. Other types, like gout and lupus-related arthritis, have their own separate causes. Understanding which type you have matters because the reason it developed shapes how doctors treat it.

Most people develop arthritis gradually, though the speed varies widely. Some people notice joint pain and stiffness that worsens over months or years. Others experience a sudden flare — a period of intense pain and swelling — that comes and goes. A few people develop arthritis after an injury, even years later. The point at which you notice symptoms is often not the point at which the condition started.

Key Takeaways

  • Osteoarthritis develops when cartilage in your joints wears down, usually from age, injury, or repeated stress on a joint.
  • Rheumatoid arthritis happens when your immune system attacks the lining of your joints, and doctors do not yet know exactly why this starts.
  • Risk factors like family history, excess weight, previous injuries, and certain jobs make arthritis more likely but do not may provide you will develop it.
  • A doctor can identify arthritis through physical examination, imaging like X-rays, and blood tests that look for specific markers.

How osteoarthritis develops over time

Osteoarthritis is the most common type of arthritis. It develops when the cartilage that cushions the ends of your bones gradually breaks down. Cartilage is smooth tissue that lets your bones glide past each other without friction. As it wears away, bone starts rubbing directly on bone, which causes pain, swelling, and stiffness.

This wear-and-tear process usually takes years. Age is the biggest risk factor — most people who develop osteoarthritis are over 50, though it can start earlier. Your joints have been moving for decades, and that repetitive motion adds up. Weight also matters: extra pounds put more stress on weight-bearing joints like your knees, hips, and lower back. A previous injury — even one that healed long ago — can speed up cartilage breakdown in that joint. Certain jobs that involve repetitive motions, like assembly line work or professional sports, increase the risk. Some people also inherit a tendency toward osteoarthritis, meaning it runs in their family.

Osteoarthritis usually affects one or a few joints rather than many at once. The knees, hips, hands, and spine are most commonly affected. It develops slowly enough that you might not notice symptoms until the cartilage damage is already significant.

How rheumatoid arthritis starts in your immune system

Rheumatoid arthritis is an autoimmune disease, meaning your immune system attacks your own body. Specifically, it attacks the synovium — the thin lining inside your joints that produces fluid to keep them moving smoothly. When the immune system inflames this lining, it causes pain, swelling, warmth, and redness in the joint. Over time, this inflammation can damage the cartilage and bone underneath.

Doctors do not yet know exactly why the immune system starts attacking joints in some people and not others. Research suggests a combination of factors is involved. Genetics play a role — if a close relative has rheumatoid arthritis, your risk is higher. Certain infections may trigger the condition in people who are genetically prone to it. Smoking also increases the risk. Hormones may be involved too, which is why rheumatoid arthritis is more common in women than men.

Unlike osteoarthritis, rheumatoid arthritis often affects multiple joints at the same time, usually on both sides of your body. Your hands, wrists, feet, and knees are frequently involved. It can develop quickly — sometimes over weeks or months — and people often feel generally unwell, with fatigue and low-grade fever alongside the joint symptoms.

Other types of arthritis and what causes them

Gout develops when uric acid builds up in your blood and forms crystals in your joints. Uric acid is a waste product your body makes when it breaks down purines, which are found in red meat, organ meats, and certain seafood. Some people's bodies produce too much uric acid, while others cannot filter it out efficiently. When crystals form, usually in the big toe, the result is sudden, severe pain and swelling.

Lupus is another autoimmune disease that can cause arthritis. Like rheumatoid arthritis, it happens when the immune system attacks the body's own tissues, but lupus can affect many organs beyond the joints, including the skin, kidneys, and heart. Psoriatic arthritis develops in some people who have psoriasis, a skin condition. The connection between the skin disease and joint inflammation is not fully understood, but the two often appear together.

Arthritis can also develop after an injury or infection. Post-traumatic arthritis can start months or years after a joint injury, even if the injury seemed to heal completely. Septic arthritis happens when bacteria or other germs enter a joint and cause infection and inflammation.

Risk factors that make arthritis more likely

Several factors increase your chances of developing arthritis, though having a risk factor does not mean you will definitely get it. Age is the strongest risk factor for osteoarthritis — your risk rises significantly after 50. Sex matters too: women are more likely to develop rheumatoid arthritis, while men are more likely to develop gout. Family history increases risk for both osteoarthritis and rheumatoid arthritis, suggesting genetics play a role.

Weight is a modifiable risk factor. Extra weight puts stress on joints that bear your body's weight, particularly the knees, hips, and lower back. Previous injuries to a joint increase the chance that osteoarthritis will develop in that specific joint later. Occupation matters if your job involves repetitive joint movements or heavy lifting. Smoking increases the risk of rheumatoid arthritis and may also speed up osteoarthritis. Some infections may trigger rheumatoid arthritis in genetically susceptible people.

How doctors identify what type of arthritis you have

A doctor typically starts by asking about your symptoms: where the pain is, how long you have had it, what makes it better or worse, and whether other family members have arthritis. They will examine your joints, looking for swelling, warmth, redness, and how much they can move. They may ask about your job, hobbies, and medical history.

Blood tests can help identify rheumatoid arthritis and other autoimmune types. A test called rheumatoid factor (RF) and another called anti-CCP antibody are often positive in rheumatoid arthritis. A test for antinuclear antibodies (ANA) may suggest lupus. For gout, a blood test measures uric acid levels. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are general inflammation markers that can be elevated in several types of arthritis.

Imaging tests show what is happening inside the joint. X-rays can reveal cartilage loss and bone damage in osteoarthritis. Ultrasound and MRI can show inflammation in the joint lining, which is common in rheumatoid arthritis. Sometimes a doctor will perform joint aspiration — inserting a needle to draw out fluid from the joint — to check for crystals (as in gout) or signs of infection.

What happens after arthritis develops

Once arthritis develops, the course varies by type. Osteoarthritis typically progresses slowly. Some people have stable symptoms for years, while others experience gradual worsening. Rheumatoid arthritis can be unpredictable — some people have periods of remission where symptoms improve significantly, while others have continuous symptoms. Early treatment can slow the progression of rheumatoid arthritis and reduce joint damage.

The good news is that having arthritis does not mean your joints will inevitably become severely damaged. Modern treatments can reduce pain, decrease inflammation, and slow progression. Physical therapy, weight management, activity modification, and medication all play roles in managing arthritis after it develops. Some people also benefit from joint injections or, in severe cases, joint replacement surgery.

Frequently Asked Questions

Can you get arthritis from cracking your knuckles?

No. Research has not found a link between cracking knuckles and arthritis development. Knuckle cracking is caused by bubbles forming and popping in the fluid around your joints, not by damage to the joint itself. You can crack your knuckles without increasing your arthritis risk.

Is arthritis always inherited?

No. While family history increases your risk, especially for rheumatoid arthritis and osteoarthritis, many people develop arthritis without any family history. Genetics load the gun, but other factors like age, weight, injury, and lifestyle pull the trigger.

Can you develop arthritis from exercise?

Regular exercise does not cause arthritis. In fact, staying active helps protect joints. However, a single traumatic injury during exercise can damage a joint and lead to post-traumatic arthritis years later. The injury itself causes the problem, not the exercise.

Does arthritis always get worse over time?

Not necessarily. Osteoarthritis progresses at different rates in different people — some people's symptoms stay stable for years. Rheumatoid arthritis can go into remission with treatment. Early diagnosis and treatment can slow progression and reduce long-term joint damage.

What is the difference between arthritis and arthralgia?

Arthralgia means joint pain without inflammation or visible joint damage. Arthritis means inflammation and structural changes in the joint. You can have arthralgia without arthritis, but arthritis usually involves arthralgia as a symptom.