Differentials
Osteoarthritis
SIGNS / SYMPTOMS
Known history of osteoarthritis.
Many joints symptomatic to a similar degree.
INVESTIGATIONS
Synovial fluid aspirate will not reveal micro-organisms.
Psoriatic arthritis
SIGNS / SYMPTOMS
Known history of inflammatory arthritis and psoriasis or family history of psoriasis.
Many joints symptomatic to a similar degree.
INVESTIGATIONS
Synovial fluid aspirate will not reveal micro-organisms.
Rheumatoid arthritis
SIGNS / SYMPTOMS
Known history of rheumatoid arthritis.
Many joints symptomatic to a similar degree.
INVESTIGATIONS
Synovial fluid aspirate will not reveal micro-organisms.
Gout
SIGNS / SYMPTOMS
Known history of gout.
INVESTIGATIONS
Synovial fluid polarising microscopy will reveal urate crystals.
Pseudogout
SIGNS / SYMPTOMS
Known history of pseudogout.
INVESTIGATIONS
Synovial fluid polarising microscopy will reveal pyrophosphate crystals.
Haemarthrosis
SIGNS / SYMPTOMS
Known history of a bleeding diathesis.
INVESTIGATIONS
Joint aspiration will reveal blood.
Trauma
SIGNS / SYMPTOMS
History of trauma to the affected joint.
INVESTIGATIONS
Joint aspiration may reveal blood.
Bursitis
SIGNS / SYMPTOMS
Examination will reveal that the swelling is external to the joint. The joint itself will move freely and painlessly.
INVESTIGATIONS
If the joint is aspirated no fluid will be obtained.
Cellulitis
SIGNS / SYMPTOMS
Examination will reveal erythematous skin overlying the joint. The joint itself will be unrestricted.
INVESTIGATIONS
If the joint is aspirated no fluid will be obtained.
Tuberculosis, extrapulmonary
SIGNS / SYMPTOMS
There may be a history of immunocompromise, origin from an endemic area, or insidious onset of symptoms.
INVESTIGATIONS
Synovial biopsy may show positive mycobacterial smears or cultures.
Lyme disease
SIGNS / SYMPTOMS
There may be a history of erythema migrans or tick bite.
INVESTIGATIONS
Lyme titre may be positive.
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