Acute joint pain/swelling

• Rheumatoid Arthritis: Persistent symmetric polyarthritis, morning stiffness lasting over 1 hour, involvement of small joints in hands and feet.
• Gout: Sudden onset monoarthritis, commonly affecting the first metatarsophalangeal joint, with severe pain and swelling, history of hyperuricemia.
• Psoriatic Arthritis: Asymmetric oligoarthritis, often with dactylitis (sausage digits), associated with a personal or family history of psoriasis.
• Reactive Arthritis: Acute onset oligoarthritis, often following a recent gastrointestinal or genitourinary infection, associated with conjunctivitis or urethritis.
• Ankylosing Spondylitis: Chronic inflammatory back pain, morning stiffness improving with exercise, associated with enthesitis and uveitis.

• Septic Arthritis: Acute monoarthritis with intense pain, swelling, erythema, and fever, often in a previously damaged joint; consider in immunocompromised patients.
• Lyme Disease: Migratory polyarthritis, often with a history of tick exposure and erythema migrans rash.
• Viral Arthritis: Polyarthralgia with a mild, self-limiting course, often associated with systemic viral symptoms (e.g., rubella, parvovirus B19).

• Osteoarthritis: Chronic joint pain and stiffness, often worse with activity, affecting weight-bearing joints like knees, hips, and hands; crepitus on movement.
• Meniscal Tear: Acute onset pain following trauma, associated with locking or giving way of the knee, joint line tenderness.
• Ligamentous Injury (e.g., ACL tear): Sudden onset pain with a history of trauma or pivoting injury, associated with swelling and instability.
• Bursitis: Localized pain and swelling, often overlying a bursa (e.g., prepatellar, olecranon), typically exacerbated by pressure or movement.
• Tendinopathy: Chronic pain at tendon insertion, associated with overuse, tenderness at the tendon site.

• Gout: Acute monoarthritis, typically affecting the big toe (podagra), associated with hyperuricemia, tophi, and birefringent needle-shaped crystals on joint aspiration.
• Pseudogout (Calcium Pyrophosphate Deposition Disease): Acute monoarthritis, commonly in the knee or wrist, chondrocalcinosis on X-ray, rhomboid-shaped crystals on joint aspiration.

• Haemarthrosis: Sudden onset of swelling in a joint following trauma, often associated with a bleeding disorder or anticoagulant therapy.
• Neoplastic Causes (e.g., Synovial Sarcoma): Progressive joint pain and swelling, possibly with a mass, not associated with trauma or systemic symptoms.
• Osteonecrosis (Avascular Necrosis): Insidious onset of pain, often in the hip or knee, associated with steroid use or alcohol abuse, seen on MRI.

Sudden onset may suggest gout, septic arthritis, or trauma. Gradual onset may indicate osteoarthritis, rheumatoid arthritis, or tendinopathy. Duration of symptoms helps differentiate between acute and chronic conditions.

Inflammatory pain is typically worse in the morning and improves with activity, seen in rheumatoid arthritis and ankylosing spondylitis. Mechanical pain worsens with activity and improves with rest, as seen in osteoarthritis and tendinopathies.

Systemic symptoms like fever, malaise, and weight loss may suggest septic arthritis, rheumatoid arthritis, or malignancy. Skin changes such as a psoriatic rash suggest psoriatic arthritis. Eye symptoms may indicate ankylosing spondylitis or reactive arthritis.

Monoarthritis may indicate gout, septic arthritis, or trauma. Oligoarthritis may suggest psoriatic arthritis or reactive arthritis. Polyarthritis can be seen in rheumatoid arthritis or viral arthritis.

• Past Medical History: History of autoimmune diseases (e.g., rheumatoid arthritis, psoriasis), previous joint disease, or surgeries.
• Drug History: Use of immunosuppressants, anticoagulants, diuretics (thiazides can precipitate gout).
• Family History: Autoimmune diseases, gout, or connective tissue disorders.
• Social History: Alcohol use (risk of gout), occupational hazards (repetitive strain injuries), travel history (exposure to infections like Lyme disease).

• Full Blood Count (FBC): May show leukocytosis in septic arthritis or anemia in chronic inflammatory conditions.
• C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR): Raised in inflammatory and infective causes like rheumatoid arthritis and septic arthritis.
• Uric Acid Levels: Raised in gout.
• Rheumatoid Factor (RF) and Anti-Citrullinated Protein Antibody (ACPA): Positive in rheumatoid arthritis.
• Antinuclear Antibody (ANA): Positive in connective tissue diseases such as lupus.
• Blood Cultures: Positive in septic arthritis.

• X-Ray: May show joint space narrowing in osteoarthritis, erosions in rheumatoid arthritis, chondrocalcinosis in pseudogout.
• Ultrasound: Useful for detecting effusions, synovitis, and guiding joint aspiration.
• MRI: More detailed imaging for detecting soft tissue abnormalities, early osteonecrosis, or subtle fractures.

Synovial fluid analysis can reveal crystal-induced arthritis (urate crystals in gout, calcium pyrophosphate crystals in pseudogout), infection (e.g., purulent fluid, positive Gram stain in septic arthritis), or inflammation (elevated white cell count in inflammatory arthritis).