- Inflammatory types of arthritis (e.g., rheumatoid arthritis)
- Septic arthritis
- Reactive arthritis
- Gout or pseudogout
- Lyme disease
Diagnosing a Warm Joint
To distinguish between these conditions, your doctor will perform a physical examination. Along with a warm joint, your doctor will examine your joints for signs of swelling, redness, and tenderness. If there is redness, along with warmth, your doctor may suspect septic arthritis or gout. Swelling is typically indicative of active inflammation or joint effusion. If tenderness is localized, it could point to bursitis or muscle injury. Range of motion will be assessed passively (your doctor moves the affected joint) and actively (you move your own joint). Septic arthritis is associated with significantly reduced range of motion, often occurring suddenly. The examination may reveal other visible signs of disease, such as rheumatoid nodules or gout tophi. A rash, called erythema migrans, often accompanies Lyme disease and is its primary characteristic. This rash can precede arthritis by months or years.
Your doctor will also take note of whether a single joint is affected or multiple joints. When a single joint is affected, called monoarthritis, septic arthritis and gout are typically suspected. When more than one joint is affected, reactive arthritis and rheumatoid arthritis are chief suspects.
While all of the visible signs gathered during physical examination are significant and help to formulate a diagnosis, your doctor will likely need to perform a joint aspiration to obtain more information. The joint fluid is tested in a laboratory. The appearance of the joint fluid, microscopic examination (looking for crystals and bacteria), and chemical analysis can be revealing.
Other laboratory tests may be ordered too, such as a complete blood count, sedimentation rate, CRP, uric acid, rheumatoid factor. Along with the aforementioned blood tests, your doctor may request imaging studies of the affected joint, such as x-ray, MRI, CT scan, or ultrasound.
Treatment of a Warm Joint
While a warm joint is not an uncommon finding, the cause must be pinned down to rule out serious conditions. Septic arthritis, the most serious cause of a warm or hot joint and greatest concern, is associated with a mortality of up to 11%. One-third of septic arthritis patients develop permanent joint damage. Following a joint aspiration and identification of the infectious agent, antibiotic therapy is critical for successful treatment of septic arthritis. If an infected joint replacement is involved, an orthopedic surgeon must be consulted. There is no time to waste when determining the cause of a warm joint and even less time to waste when the cause is infection.
The Bottom Line
Accurate diagnosis and appropriate treatment for a warm joint is essential. A warm joint should not be ignored, especially if it has come on suddenly and has significantly affected range of motion or your ability to put weight on it.
Guideline for the Management of the Hot Swollen Joint in Adults With a Particular Focus on Septic Arthritis. Journal of Antimicrobial Chemotherapy. Weston and Coakley. July 19, 2006.
The Single Hot Joint. Calin A. and Fries J. American Society of Contemporary Medicine and Surgery. October 1976.
Hot Swollen Joints. Patient.co.uk. Dr. Laurence Knott. 3/22/2010.