ACUTE MONARTHRITIS
Quick Tips to Diagnosis

Family physicians may frequently find themselves presented with a patient complaining of symptoms of Acute Monoarthritis. The differential diagnosis is large, but the following tips may help. These are the possibilities a Rheumatologist will consider when seeing a similar patient.

Septic arthritis - suspect if: Onset over hours or days, fever, chills, intense redness and swelling. Consider especially in the immune deficient host or with a previously damaged joint.

Gonococcal arthritis - suspect if: Rapid onset, fever, younger age, recent new sexual contacts, migratory arthritis then developing a monoarthritis, septic tenosynovitis, urethritis

Crystal arthritis - suspect gout if: diuretic use, involvement of 1st MTP, tarsal joints, ankles, knees. History of previous self limited attacks. Assess for tophi and a history of renal stones. Suspect pseudogout with older age and involvement of knee and wrist. Chondrocalcinosis may be found on x-ray.

Hemarthrosis - suspect if: Coagulopathy is present or the patient is on anticoagulant therapy . Consider the possibility with associated trauma, especially in large joints.

Trauma or overuse - suspect if: There is a compatible history, especially of an accident or work trauma. Suspect Internal derangement if: there is knee or shoulder involvement with episodic locking or giving away.

Sarcoidosis (Lofgren's syndrome) - suspect if: Acute onset, periarticular swelling and intense redness of ankles, and erythema nodosa, which is frequently found on the anterior parts of the legs.

Monoarticular presentation of systemic arthritis (Psoriatic, Reiter's, Rheumatoid arthritis etc, may present initially with one joint) - suspect if: associated conjunctivitis, urethritis, inflammatory low back pain, skin rash on palm or sole, psoriasis, abdominal pain, diarrhoea, rectorragia. Rheumatoid arthritis is more an exclusion diagnosis.

Arthrocentesis is mandatory in monoarthritis to rule out a septic joint. If suspected, antibiotic therapy should be initiated and continued until result of culture of synovial fluid is available. A decision to continue antibiotics can be made, based on the culture result.

- Denis Choquette

Thanks to Dr. Diane Wilson, community based Rheumatologist in Lunenberg Nova Scotia for reviewing the draft copy of this article.