Arthritis is inflammation in one or more joints that causes pain, stiffness, and sometimes swelling

Arthritis is not a single disease — it is a group of conditions that damage the joints where bones meet. The two most common types are osteoarthritis, which develops when the protective cartilage in a joint wears down over time, and rheumatoid arthritis, an autoimmune condition where the body's immune system attacks the joint lining. Other types include gout, lupus-related arthritis, and psoriatic arthritis, each with different causes and patterns.

The damage happens inside the joint. In osteoarthritis, the smooth cartilage that lets bones slide past each other breaks down, so bone rubs on bone. In rheumatoid arthritis, the immune system inflames the synovium — the membrane that lines the joint — which then damages the cartilage and bone underneath. Either way, the result is pain when you move, stiffness that may be worse in the morning, and sometimes visible swelling.

Arthritis most often affects the hands, knees, hips, and spine, though it can develop in any joint. It is more common as you age, but younger people can develop it too, especially rheumatoid arthritis. The symptoms range from mild to severe, and they can stay the same or get worse over time depending on the type and how well it is managed.

Key Takeaways

  • Arthritis is inflammation in joints caused either by cartilage wear (osteoarthritis) or immune system attack (rheumatoid arthritis), and there are several other types with different causes.
  • The main symptoms are joint pain, stiffness especially in the morning, swelling, and reduced range of motion, and they may affect one joint or many.
  • Osteoarthritis develops slowly over years and is more common in older adults, while rheumatoid arthritis can start suddenly and affect people of any age.
  • A doctor can diagnose arthritis through physical examination, blood tests, and imaging like X-rays, and early diagnosis helps slow progression and manage pain.

The main symptoms and how they feel

Pain is the first symptom most people notice. It may be sharp when you move the joint, or a dull ache that is always there. The pain often gets worse with activity and improves with rest, though in some types of arthritis it may feel worse in the morning and ease as you move around.

Stiffness is common, especially when you first wake up or after sitting still for a while. Your joint may feel locked or hard to bend. In osteoarthritis, morning stiffness usually lasts less than an hour. In rheumatoid arthritis, stiffness can last several hours and affect multiple joints at once.

Swelling happens when fluid builds up in the joint or the surrounding tissue becomes inflamed. The joint may look puffy or feel warm to the touch. Some people also notice redness around the joint. Swelling can make the joint feel stiff and limit how far you can move it.

You may also notice that the joint does not move as far as it used to — this is called reduced range of motion. Gripping, climbing stairs, or opening jars may become harder. Some people develop a grinding or popping sensation in the joint, which happens when the cartilage surface becomes rough.

Osteoarthritis versus rheumatoid arthritis: the key differences

Osteoarthritis develops slowly, usually over many years. It is caused by wear and tear on the joint, so it is more common in older adults and in joints that have been injured or overused. It typically affects one side of the body more than the other — for example, your right knee more than your left — and it usually starts in the hands, knees, hips, or spine. The pain and stiffness are usually worse in the morning and improve as you move, though activity can make it worse again.

Rheumatoid arthritis can start suddenly, sometimes over a few weeks. It is an autoimmune disease, so it can develop at any age, including in younger people. It almost always affects both sides of the body equally — both hands, both knees — and it often affects multiple joints at once. Morning stiffness lasts longer, sometimes three hours or more. People with rheumatoid arthritis often feel tired and may run a low fever. Blood tests can detect specific markers that show the immune system is attacking the joints.

The two types need different treatment approaches. Osteoarthritis is managed with pain relief, exercise, and sometimes injections or surgery. Rheumatoid arthritis requires medications that calm the immune system, often started early to prevent permanent joint damage. Knowing which type you have matters because the wrong treatment will not help.

When to see a doctor about joint pain

See a doctor if joint pain lasts more than a few weeks, or if it is bad enough to limit what you can do. You should also go if you notice swelling that does not go down, or if stiffness in the morning lasts more than 30 minutes. If pain comes on suddenly after an injury, that needs evaluation too, though it may be a sprain rather than arthritis.

Tell your doctor which joints hurt, when the pain started, what makes it better or worse, and whether you have noticed swelling or stiffness. If the pain affects both sides of your body equally, or if you feel tired or feverish along with the joint pain, mention that — those details help your doctor figure out which type of arthritis you might have.

Your doctor may order blood tests to look for rheumatoid factor or other markers of autoimmune arthritis, and X-rays or ultrasound to see the joint structure. Early diagnosis matters because some types of arthritis cause permanent damage if left untreated, and starting treatment early can slow that damage.

Risk factors that make arthritis more likely

Age is the strongest risk factor for osteoarthritis. The older you are, the more likely you are to develop it. Rheumatoid arthritis can start at any age, but it is most common in people over 40.

Family history matters for both types. If your parents or siblings have arthritis, your risk is higher. For rheumatoid arthritis, genetics play a larger role — certain genes make the condition more likely.

Joint injury increases the risk of osteoarthritis in that joint later on. A serious knee injury in your 30s, for example, can lead to arthritis in that knee by your 50s or 60s. Repetitive stress on a joint — from certain jobs or sports — can also speed up cartilage wear.

Being overweight puts extra stress on weight-bearing joints like the knees and hips, which increases osteoarthritis risk. Smoking raises the risk of rheumatoid arthritis. Women are more likely to develop rheumatoid arthritis than men, though osteoarthritis affects both sexes roughly equally.

What happens if arthritis is not treated

Untreated osteoarthritis usually gets worse slowly. The cartilage continues to wear away, pain increases, and the joint may become less stable. Over time, bone spurs can form, and the joint may become visibly deformed. You may lose the ability to do everyday tasks like opening jars or climbing stairs. However, osteoarthritis does not usually spread to other joints on its own — it stays in the joints that are already affected.

Untreated rheumatoid arthritis is more serious. The immune system continues to attack the joint lining, which damages the cartilage and bone underneath. This damage is permanent and can happen quickly, sometimes within months. Over time, the joint may become deformed and lose function. Rheumatoid arthritis can also affect organs like the heart and lungs if left untreated.

Starting treatment early, especially for rheumatoid arthritis, can slow or stop this damage. Even for osteoarthritis, managing pain and staying active helps preserve joint function and quality of life. This is why seeing a doctor early matters.

How doctors diagnose arthritis

Your doctor will start by asking about your symptoms — where the pain is, when it started, what makes it better or worse, and whether other family members have arthritis. They will examine the affected joints, looking for swelling, warmth, redness, and how far the joint can move.

Blood tests can show signs of rheumatoid arthritis. The rheumatoid factor test and anti-CCP antibody test are positive in many people with rheumatoid arthritis but negative in people with osteoarthritis. A test called ESR (erythrocyte sedimentation rate) or CRP (C-reactive protein) shows whether there is inflammation in the body. These tests help your doctor tell the two types apart.

Imaging is usually the next step. X-rays show bone damage and cartilage loss. Ultrasound can show swelling in the joint lining. MRI gives a detailed picture of the joint and surrounding tissue. The imaging confirms which joints are affected and how much damage has occurred.

Once your doctor knows which type of arthritis you have, they can recommend treatment. For osteoarthritis, that might be pain relievers, physical therapy, and lifestyle changes. For rheumatoid arthritis, it usually includes medications that slow the immune attack, started as soon as possible to prevent permanent damage.

Frequently Asked Questions

Can arthritis go away on its own?

Osteoarthritis does not go away — the cartilage damage is permanent. However, pain can be managed and you can stay active with the right approach. Rheumatoid arthritis also does not go away, but medications can put it into remission where symptoms nearly disappear. Without treatment, rheumatoid arthritis usually gets worse.

Is arthritis the same as joint pain from exercise?

No. Muscle soreness from exercise usually goes away within a few days. Arthritis pain lasts weeks or months, often gets worse with activity, and may be accompanied by swelling or stiffness. If joint pain does not improve after a week of rest, see a doctor.

Can young people get arthritis?

Yes. Rheumatoid arthritis can start at any age, including in children and teenagers. Osteoarthritis is less common in young people but can develop after a serious joint injury. If you have persistent joint pain, swelling, or stiffness, see a doctor regardless of your age.

Does weather affect arthritis pain?

Many people report that arthritis pain gets worse in cold, damp weather or when barometric pressure drops. The reason is not fully understood, but it may be related to changes in fluid pressure inside the joint or changes in how muscles and tendons respond to temperature. This is real for many people, though it does not happen to everyone.

What is the difference between arthritis and arthralgia?

Arthralgia is joint pain without inflammation or damage. Arthritis is inflammation in the joint that causes pain, swelling, and sometimes permanent damage. You can have arthralgia from many causes — a sprain, overuse, or even anxiety — without having arthritis. A doctor can tell the difference through examination and blood tests.