Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Distinguish an inflammatory musculoskeletal syndrome from mechanical, periarticular, neuropathic and systemic mimics, identify patients who cannot wait, and choose focused tests without treating a laboratory result as the diagnosis.
The inflammatory–mechanical distinction is a probability judgement, not a binary test. Establish onset, tempo, distribution, stiffness duration, rest and night symptoms, load response, swelling, systemic illness and functional consequences. Examine the symptomatic region and screen other joints, skin, nails, eyes and entheses. An older patient may have osteoarthritis and new inflammatory arthritis simultaneously; an athlete may have mechanical pain with an inflammatory disease in the background.
Pain location is often misleading. Joint-line pain with restriction of both active and passive movement supports an intra-articular source. Pain on active or resisted movement with relatively preserved passive range suggests tendon or muscle. Focal bursal tenderness, dermatomal sensory change, allodynia or pain reproduced by spinal movement redirects assessment. Hip disease may present at the knee and cervical disease may present around the shoulder or arm.
Investigations should resolve uncertainty that changes care. Persistent clinical synovitis merits early specialist assessment rather than serial screening panels. Serum urate neither confirms nor excludes an acute gout flare, autoantibodies change probability rather than define symptoms, and early radiographs may be normal. Safety-net any provisional mechanical diagnosis with a review point and explicit triggers such as swelling, systemic illness, neurological change or failure to improve.
Rheumatoid arthritis, spondyloarthritis, crystal arthritis and connective-tissue disease generate synovial, entheseal or periarticular inflammation through distinct immune and inflammatory pathways.
Osteoarthritis, tendinopathy, bursitis and structural injury produce pain when load exceeds the capacity of cartilage, tendon, bone or supporting soft tissue.
Infection, malignancy, neuropathy, vascular disease and referred visceral pain may resemble a joint or muscle disorder and alter the urgency of assessment.
Cytokines, synovial vascularity and inflammatory cell recruitment sensitise nociceptors, causing rest pain, prolonged stiffness, warmth, swelling and impaired movement.
Structural degeneration or focal soft-tissue injury activates pain during movement, compression or resisted loading, usually easing when the provoking demand stops.
Pain, fear and reduced activity weaken muscle and alter movement, so inflammatory and mechanical mechanisms can coexist and reinforce disability over time.
Soft swelling, warmth, prolonged morning stiffness, rest pain and restricted movement across several joints suggests active synovitis, especially with fatigue, weight loss or extra-articular features.
Pain linked to use, brief stiffness, crepitus, bony change or focal pain on resisted movement supports osteoarthritis or regional soft-tissue disease, while acknowledging overlap.
Acutely painful restricted joint with fever, immunosuppression, prosthesis or recent procedure is septic arthritis until urgently assessed and sampled; absence of fever is not reassuring.
Back pain beginning young, improving with movement, waking the patient in the second half of the night, alternating buttock pain, enthesitis or uveitis supports spondyloarthritis.
Persistent synovitis, prolonged morning stiffness, nocturnal symptoms and systemic or extra-articular features support rheumatoid arthritis or a spondyloarthritis phenotype.
Activity-related pain, brief stiffness, bony enlargement, crepitus or reproducible tendon and bursal loading suggests a mechanical or periarticular source.
Abrupt severe monoarthritis, fever, immunosuppression or marked inflammatory response requires aspiration because clinical appearance cannot safely distinguish sepsis from crystals.
Dermatomal symptoms, weakness, altered reflexes or pain unrelated to joint movement suggests root, peripheral nerve or referred visceral disease.
Night pain unrelated to position, focal bone pain, neurological deficit, vascular change, constitutional symptoms or organ-specific features should expand assessment beyond rheumatology.
Unrecognised persistent synovitis can cause erosive damage, tendon failure, deformity, disability and extra-articular disease before the diagnostic label becomes secure.
Attributing red flags to a benign mechanical explanation can delay source control, oncological diagnosis or treatment of threatened neurological structures.
Avoidance, sleep loss and reduced conditioning can perpetuate weakness, falls, work loss and dependence even after the initiating tissue injury settles.
Duration helps, but inability to move from pain, poor sleep and osteoarthritis can also create morning stiffness; swelling and distribution provide stronger context.
Restriction of passive as well as active range supports an articular or capsular process, while isolated resisted pain points toward a muscle–tendon unit.
Inflammatory arthritis can leave secondary osteoarthritis, tendinopathy and central pain amplification, so disease control may not remove every symptom.
Normal markers, serology or radiographs lower selected probabilities but cannot erase objectively documented synovitis or a dangerous clinical trajectory.
Watching a patient rise, grip, reach and walk often distinguishes pain inhibition, weakness, stiffness and instability better than isolated palpation.
Calling pain inflammatory solely because an NSAID helped; mechanical pain may also improve with anti-inflammatory analgesia.
Using age to dismiss new inflammatory disease or to attribute every symptom to radiographic osteoarthritis.
Requesting broad autoimmune panels before defining the clinical phenotype and then chasing incidental low-specificity results.
Assuming crystal identification makes bacterial culture unnecessary in a hot swollen joint.
Failing to examine the joint above, joint below, spine, skin and nails when the painful site alone does not explain symptoms.
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A 42-year-old has eight weeks of bilateral MCP swelling, ninety minutes of morning stiffness and impaired grip. CRP and rheumatoid factor are normal. What is the best next action?
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes