How can I differentiate between osteoarthritis and other types of arthritis in a patient presenting with joint pain?

To differentiate between osteoarthritis (OA) and other types of arthritis in a patient presenting with joint pain, consider the following clinical features and diagnostic approaches:

• Clinical Diagnosis of Osteoarthritis:

  Diagnose osteoarthritis clinically without imaging in people who are 45 or over, have activity-related joint pain, and have either no morning joint-related stiffness or morning stiffness that lasts no longer than 30 minutes ¹. Imaging is not routinely used to diagnose osteoarthritis unless there are atypical features or features that suggest an alternative or additional diagnosis ¹.

• Atypical Features Suggesting Other Diagnoses:

  Atypical features that may suggest an alternative or additional diagnosis include a history of recent trauma, prolonged morning joint-related stiffness, rapid worsening of symptoms or deformity, the presence of a hot swollen joint, or concerns that may suggest infection or malignancy ¹.

• Considering Gout:

  Suspect gout in people presenting with rapid onset (often overnight) of severe pain together with redness and swelling, particularly in one or both first metatarsophalangeal (MTP) joints, or the presence of tophi ⁴. Gout should also be considered if there is rapid onset of severe pain, redness, or swelling in other joints such as the midfoot, ankle, knee, hand, wrist, or elbow ⁴. Measure the serum urate level to confirm a clinical diagnosis of gout (360 micromol/litre or more) ⁴. If the serum urate level is below 360 micromol/litre during a flare and gout is strongly suspected, repeat the measurement at least two weeks after the flare has settled ⁴. Joint aspiration and microscopy of synovial fluid can be considered if the diagnosis remains uncertain ⁴. Imaging with X-ray, ultrasound, or dual-energy CT may be considered if joint aspiration cannot be performed or the diagnosis remains uncertain ⁴.

• Other Inflammatory Conditions:

  Assess the possibility of septic arthritis, calcium pyrophosphate crystal deposition, and inflammatory arthritis in people presenting with a painful, red, swollen joint ⁴. If septic arthritis is suspected, refer immediately according to the local care pathway ⁴. Chronic gouty arthritis should be considered in people presenting with chronic inflammatory joint pain ⁴.