Early osteoarthritis symptoms typically involve a single joint. When only one joint is affected, the condition is referred to as monoarthritis. As symptoms first appear, it's important to distinguish if the cause of the joint pain and swelling is osteoarthritis or another type of monoarthritis.
Possible Causes of Monoarthritis
Diseases that deposit crystals in the joint fluid (such as gout), infection, and trauma or injury are the other most common causes of monoarthritis besides osteoarthritis.
Once a patient shows signs of monoarthritis, the doctor uses the patient's medical history, a physical examination, x-rays, and additional tests (i.e., a microorganism culture to determine if there is infection; arthrocentesis to examine the fluids in the joints) to formulate an accurate diagnosis and determine the possibility of osteoarthritis.
Information that is derived from the patient's medical history and physical examination can give strong clues regarding the cause of the monoarthritis. For example:
- a sudden onset of joint pain can be indicative of a fracture, injury or loose tissue moving in the joint
- onset of joint pain over several hours up to 2 days is usually indicative of infection, inflammatory arthritis, or crystal deposition disease
- a slow onset of joint pain over days or weeks points to osteoarthritis, an inactive infection, or a tumor
- a history of intravenous drug use or immunosuppression (weakened immune system) may indicate a risk for septic arthritis
- previous acute attacks of monoarthritis in other joints suggest crystal deposition disease or inflammatory arthritis
- a long course of corticosteroid drugs may suggest the monoarthritis is from infection or avascular necrosis
- psoriatic patches or pitting of nails suggest psoriatic arthritis is involved
- the presence of tophi (bumps around joints) are signs of gout
- eye inflammation and low back pain point to ankylosing spondylitis
Diagnostic Tests Determine Type of Monoarthritis
Along with the information gathered from the medical history and physical examination, x-rays are taken to capture an image of the arthritic joint. An arthrocentesis or synovial fluid analysis also is used to distinguish between the types of monoarthritis. The joint fluid is cultured to look for bacterial infection. It also can reveal crystals in the fluid. Depending on the appearance of the joint fluid and the blood counts, it can be categorized as non-inflammatory, inflammatory or hemorrhagic.
Because a bacterial joint infection is considered an emergency, people with a suspected (but not confirmed) infection are often given antibiotics, just in case, until a clear diagnosis can be made.
To diagnose osteoarthritis, there must be:
- insidious (slow) onset of joint pain
- joint effusion
- no evidence of infection
- no evidence of gout-related crystals in the joint fluid
- no injuries or trauma to surrounding soft tissues
- synovial fluid analysis consistent with non-inflammatory arthritis
Diagnosing Acute Monoarthritis in Adults: A Practical Approach for the Family Physician. July 1, 2003. American Family Physician.
Specific Types of Monoarthritis. Primer on the Rheumatic Diseases. p.159. Published by the Arthritis Foundation.