Monoarthritis, also called monoarticular arthritis, refers to joint inflammation that affects one joint. Monoarthritis is not a type of arthritis itself, but rather a descriptor of the arthritis. Arthritis that affects more than one joint is called polyarticular.

Often, monoarthritis can appear suddenly and cause joint discomfort that ranges from moderate to severe. The condition has several potential underlying causes, including infection, gout, and certain autoimmune diseases.

Read on to find out more about monoarthritis, including its symptoms, diagnosis, and treatment.

Monoarthritis can be a symptom of an underlying infection or other medical condition. Because there are multiple causes, diagnosis can be challenging to doctors, as they seek to rule things out.

Let’s go over some of the most common causes of monoarthritis.


Conditions that cause crystal deposits to build up in the body are the most common culprits behind monoarthritis. This usually means gout and pseudogout.

Gout happens when uric acid crystals build up in your body and start to form a deposit at a joint. Your body produces uric acid when it breaks down purines. These are substances found in things like alcoholic beverages, red meat, and drinks sweetened with fructose.

A gout flare can last days to weeks, and often begins in the big toe or a lower limb. It can cause intense pain and noticeable swelling.


Infections are also a common underlying cause of monoarthritis.

This can be the case in septic (or infectious) arthritis, which occurs due to an underlying infection, typically in the knees or hips. In addition to pain and joint swelling, septic arthritis is often accompanied by typical signs of infection, including fever, chills, and fatigue.

Gonococcal arthritis (arthritis due to a gonorrhea infection) is the most common cause of monoarthritis in young, sexually active people.

If you have had a joint replacement, infection of the areas around the replacement can also potentially cause monoarthritis. Contact your surgeon right away if you’ve had a joint replacement and are experiencing troubling pain or signs of infection. You may need treatment with antibiotics.

Other causes

In addition to gout and septic arthritis, there are other medical conditions that can cause monoarthritis. These include:

Monoarthritis can occur in 5 to 20 percent of patients whom a doctor will later diagnose with rheumatoid arthritis.

But a lot of the time, the above conditions affect more than one joint. Depending on the cause, it’s possible for monoarthritis to progress to inflammation in other joints over time.

Monoarthritis tends to cause acute pain. This means the pain seems to come on suddenly, usually within hours to days.

Some monoarthritis symptoms may include:

  • pain that usually worsens with movement
  • swelling
  • warm feeling in the joint
  • weakness

A broader range of symptoms depends upon the underlying cause. For example, if RA is causing your monoarthritis, you’ll usually experience joint stiffness in the morning that improves in an hour or less.

Conditions like gout may not cause joint stiffness specifically in the morning. Infections causing monoarthritis may be accompanied by fever, chills, and aches.

Because monoarthritis can have underlying causes that are serious medical issues, it’s important you consult a medical professional. Prompt treatment can prevent a case of monoarthritis from worsening, or causing long-term health complications.

Questions your doctor may ask when evaluating your monoarthritis include:

  • When did the pain or discomfort begin?
  • How would you describe the feeling of the joint?
  • Have you experienced recent trauma/accident or surgery?
  • Do you have any chronic health conditions?
  • What medications do you take?

Your doctor will then likely conduct a physical examination of the affected joint. They’ll observe the joint and move it around gently. If you have septic arthritis or an infection, you may not be able to move the joint at all.

Examinations may be uncomfortable, but shouldn’t cause you excessive pain. It’s important you communicate with your doctor how you’re feeling.

Sometimes, your doctor may be able to identify a cause based on your symptoms and medical history, which can especially be the case with gout.

Other times a healthcare professional may order additional exams or tests. This may include taking a sample of synovial fluid and sending you to get blood testing or imaging, like an X-ray or MRI.

Monoarthritis treatments depend upon the underlying cause. There are some times when monoarthritis can be an emergency. This includes if septic arthritis or another acute infection is suspected.

Other times, your healthcare professional will usually treat you with conservative measures, like:

If you’re diagnosed with gout, your doctor may prescribe medications like colchicine to reduce excess uric acid buildup. They may also recommend a diet that’s low in purines, the substances that can cause crystal deposits that lead to gout.

If you have an active infection, your doctor may prescribe intravenous or oral antibiotics. It’s important to start antibiotics right away and take them exactly as directed. Conditions like septic arthritis can have serious effects if untreated, including coma and death.

Certain causes of monoarthritis are medical emergencies, especially if accompanied by symptoms other than joint pain. Seek immediate medical attention for monoarthritis if:

  • you’ve recently had surgery and experience sudden pain, swelling, warmth, or redness to your joint, which can be a sign of infection
  • you have a high fever along with your arthritis symptoms, which can also indicate possible infection
  • you have joint pain and swelling after an injury — you may have a fracture or sprain that requires attending

Even if you don’t think your pain is an emergency, consider making an appointment with your doctor if your symptoms interfere with your quality of life. Pain, swelling or redness in a joint should always be evaluated by a professional.

Monoarthritis causes pain in one joint and can indicate several different underlying conditions, including gout or infection. Treatments can range from conservative methods like rest and pain medication to immediate treatment with antibiotics.

In evaluating you for monoarthritis and its causes, your doctor will collect a symptom history, conduct a physical exam, and may order further diagnostic tests.

If your joint pain comes on suddenly, is ongoing, and affects your ability to function in daily life, these are signs to seek care.