Arthritis develops when cartilage in your joints wears down or your immune system attacks joint tissue

You do not "get" arthritis the way you catch a cold. Arthritis is not contagious. Instead, it develops over time through a combination of factors — some you can control and some you cannot. The two most common types, osteoarthritis and rheumatoid arthritis, start differently but both end with pain, stiffness, and swelling in your joints.

Osteoarthritis happens when the cartilage that cushions the ends of your bones gradually breaks down. This usually takes years. Rheumatoid arthritis is different — your immune system mistakenly attacks the lining of your joints, causing inflammation. Both can make everyday tasks harder, but understanding what causes them helps you know what to watch for and what you might be able to slow down.

Key Takeaways

  • Osteoarthritis develops from wear and tear on joints over decades, while rheumatoid arthritis is an autoimmune condition where your body attacks joint tissue.
  • Age, family history, previous joint injuries, and excess weight all increase your risk of developing arthritis.
  • Some risk factors you cannot change, but staying active, maintaining a healthy weight, and protecting your joints from injury may slow progression.
  • Symptoms often start gradually — morning stiffness, mild pain after activity, or swelling in one joint — and worsen over months or years.

How osteoarthritis develops over time

Osteoarthritis is the most common type of arthritis, especially as you age. It happens because the cartilage in your joints wears down gradually. Cartilage is the smooth, rubbery tissue that covers the ends of your bones and lets them glide past each other without friction. Over decades of use — walking, bending, lifting — this cartilage thins and cracks.

Once cartilage starts to break down, bone rubs against bone. Your body tries to repair the damage by growing extra bone around the joint, which causes stiffness and pain. This process usually takes 10, 20, or 30 years to develop enough that you notice symptoms. That is why osteoarthritis is far more common in people over 65, though it can start earlier if you have risk factors.

The joints most often affected are your knees, hips, hands, and spine — the places that bear weight or move a lot. You might notice one knee starts to hurt before the other, or your thumb joint becomes stiff. Osteoarthritis usually affects one side of your body more than the other.

Why rheumatoid arthritis is an autoimmune condition

Rheumatoid arthritis works completely differently. Instead of wear and tear, your immune system mistakenly identifies the lining of your joints as a threat and attacks it. This causes inflammation — swelling, warmth, and redness — that damages the joint over time. Unlike osteoarthritis, rheumatoid arthritis can develop quickly, sometimes over weeks or months.

Rheumatoid arthritis often affects multiple joints at the same time, usually on both sides of your body. You might wake up with stiff, swollen hands on both sides, or both knees might hurt. It is less common than osteoarthritis and tends to start between ages 30 and 60, though it can happen at any age.

Doctors do not fully understand why some people's immune systems attack their joints and others do not. Genetics play a role — if a parent or sibling has rheumatoid arthritis, your risk is higher. Infections and smoking may also trigger it in people who are genetically prone.

Risk factors you cannot change

Age is the strongest risk factor for osteoarthritis. The older you are, the more likely you are to develop it. Your cartilage straightforward wears down over decades.

Family history matters for both types. If your parents or siblings have arthritis, you are more likely to develop it too. For rheumatoid arthritis, certain genes make your immune system more likely to attack your joints. For osteoarthritis, you may inherit the structure of your joints or how your cartilage breaks down.

Sex affects your risk. Women are more likely to develop rheumatoid arthritis than men, especially after menopause. Osteoarthritis is also more common in women over 50.

Previous joint injuries increase your risk of osteoarthritis in that joint later on. A torn knee cartilage, a broken bone, or a severe sprain can speed up cartilage breakdown years later, even if the injury healed well.

Risk factors you may be able to influence

Weight puts extra stress on weight-bearing joints like your knees, hips, and lower back. Excess weight increases your risk of osteoarthritis in these joints. Losing weight, if you are overweight, may slow the progression of arthritis or reduce pain.

Activity level matters, but in a nuanced way. Staying active and keeping your muscles strong actually protects your joints by supporting them. However, high-impact activities or repetitive stress on one joint — like running marathons or doing the same motion for hours every day — can increase wear and tear. Moderate activity like walking, swimming, or tai chi is generally protective.

Smoking increases your risk of rheumatoid arthritis and may worsen it if you already have it. Quitting smoking can lower your risk and may help slow progression if you have been diagnosed.

Joint injuries from accidents or sports can trigger osteoarthritis in that joint years later. Protecting your joints during activities — using proper technique, wearing protective gear, and avoiding repetitive strain — may reduce this risk.

Early warning signs to watch for

Arthritis usually starts quietly. You might not notice anything for a long time, then one day a joint feels stiff or sore. Early signs include morning stiffness that lasts more than 30 minutes, pain or aching after activity, or mild swelling in a joint. Some people notice their hands or feet feel puffy when they wake up.

For osteoarthritis, pain often gets worse as the day goes on or after you use the joint. For rheumatoid arthritis, morning stiffness is often the first sign and may last an hour or more. You might also feel generally tired or notice swelling in multiple joints on both sides of your body.

These early signs do not mean arthritis will definitely develop or progress quickly. Many people have mild symptoms that stay the same for years. But if you notice joint pain, stiffness, or swelling that lasts more than two weeks, it is worth mentioning to your doctor at your next visit.

When to talk with your doctor

You do not need to wait for severe symptoms. If you have joint pain, stiffness, or swelling that lasts more than two weeks, mention it to your primary care doctor. They can examine your joints, ask about your family history, and order blood tests or imaging if needed. Early diagnosis of rheumatoid arthritis is especially important because treatment started early can slow joint damage.

Tell your doctor if you have a family history of arthritis, if you have had a previous joint injury, or if you do work or hobbies that put repetitive stress on one joint. This information helps them assess your risk and watch for early signs.

You should seek care sooner if you have sudden swelling in multiple joints, severe pain that limits your movement, or warmth and redness around a joint. These can be signs of rheumatoid arthritis or other conditions that benefit from prompt treatment.

Frequently Asked Questions

Can arthritis run in families?

Yes. If a parent or sibling has arthritis, your risk is higher for both osteoarthritis and rheumatoid arthritis. However, having a family history does not mean you will definitely develop it — it means you are more likely to. Lifestyle choices and other factors also play a role.

Does exercise cause arthritis?

Moderate exercise like walking, swimming, or cycling does not cause arthritis and may actually protect your joints by keeping muscles strong. High-impact activities done repeatedly or with poor technique can increase wear and tear, but normal activity is not a risk factor.

Can you get arthritis from cracking your knuckles?

No. Cracking your knuckles does not cause arthritis. Studies have found no link between knuckle cracking and arthritis development. Arthritis develops from cartilage breakdown, immune system problems, or injury — not from the popping sound your joints make.

Is arthritis the same as joint pain?

Not necessarily. Many things cause joint pain — muscle strain, bursitis, or temporary inflammation. Arthritis is a specific condition where the joint itself is damaged. If you have joint pain lasting more than two weeks, a doctor can determine whether it is arthritis or something else.

Can you prevent arthritis if it runs in your family?

You cannot prevent arthritis entirely if you are genetically prone, but you may be able to delay it or reduce symptoms. Staying at a healthy weight, staying active with low-impact exercise, protecting your joints from injury, and not smoking all lower your risk or slow progression.