Reasoning GP · Algorithm · 1-page summary
Joint pain and swelling in adults
For: adults with pain or swelling in one or more joints in primary care. Not for: children (limping child algorithm); a single-joint injury (fractures, ankle or elbow algorithms); back pain alone (back pain algorithm).
Core rule: treat an acute hot, swollen joint as septic arthritis until infection is excluded — fever may be absent — and refer persistent synovitis urgently, whatever the bloods and X-ray show.
0Stop — call 999 now
- Hot, swollen joint in a septic or unstable patient → 999; do not delay antibiotics or transfer for aspiration or imaging.
- New breathlessness, dry cough or fever on methotrexate (pneumonitis) → 999 if unstable, otherwise Same-day hospital; withhold methotrexate.
- Suspected GCA with any visual symptom, diplopia or cranial ischaemia → start prednisolone now + Same-day ophthalmology / acute GCA assessment.
1Triage — onset and pattern
| Onset | Think |
|---|---|
| Hours, one hot joint | Septic until excluded; gout, CPPD, haemarthrosis, reactive |
| Days–weeks | Early RA, psoriatic, reactive, viral, Lyme |
| >3 months | OA, established RA, psoriatic, axial SpA, tophaceous gout |
| Inflammatory | Morning stiffness >30 min, soft swelling, warmth, better with use |
| Mechanical | No or ≤30 min stiffness, bony swelling, worse with use |
2Screen — serious causes
- Hot, swollen joint ± fever (prosthesis, immunosuppressed, on a biologic) → Same-day hospital: aspiration, blood cultures.
- Pustular rash, tenosynovitis, migratory arthralgia → disseminated gonococcal infection → Same-day hospital.
- Age ≥50 + new headache, jaw claudication, scalp tenderness → GCA: prednisolone 40–60 mg today + Same-day fast-track. Vasculitis with organ involvement → Same-day.
- Haemarthrosis: haemophilia → Same-day haemophilia centre; significant bleed on anticoagulant → urgent haematology advice.
- Weight loss, night sweats, bone pain → Urgent X-ray; sarcoma on X-ray → consider suspected cancer pathway (young people: ≤48 h).
- Persistent synovitis — small joints of hands/feet, >1 joint or ≥3 months → rheumatology ≤3 working days; seen within 3 weeks of referral (QS33).
3Assess
☐ Count joints; soft vs bony swelling; warmth ☐ Skin, nails, eyes, tophi ☐ FBC, CRP + ESR, renal, liver; RF + anti-CCP if RA suspected ☐ Urate (may be normal in a flare) ☐ STI NAAT if relevant ☐ X-ray only if it changes management. No ANA screen; aspiration only by trained clinicians.
4Classify — only if blocks 0–2 are negative
- Gout — first MTP, ankle or knee, peaks in 12–24 h; tophi.
- CPPD — knee, older; younger or recurrent → consider calcium, phosphate, magnesium, ALP, ferritin, PTH.
- RA — symmetrical MCPs, PIPs, wrists; negative RF/anti-CCP does not exclude.
- Psoriatic / reactive / axial SpA — DIP, dactylitis, nails; 1–4 weeks after enteric or chlamydial infection; back pain >3 months, onset before 45 → rheumatology.
- OA — ≥45, activity-related pain, no or ≤30 min stiffness → clinical diagnosis.
- Uncertain → reassess; persistent swelling → refer rheumatology.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Gout flare: NSAID + PPI, colchicine or short steroid by renal, CV, GI risk. ULT: discuss after first flare; offer if recurrent, tophi, CKD 3–5, diuretics; urate <360 µmol/L.
- OA: exercise and weight support for all; topical NSAID first-line for knee; oral NSAID + PPI after risk check; no routine paracetamol or weak opioids; no strong opioids.
- Suspected RA: NSAID + PPI after risk check; steroid only on rheumatology advice; never start a DMARD before specialist diagnosis.
- Reactive: NSAID first-line; chlamydia → sexual health (NAAT, partner notification) — no doxycycline for the arthritis alone.
6Refer routinely
- Rheumatology: flare of established arthritis, gout refractory to ULT, recurrent CPPD, suspected SLE/connective tissue disease.
- Orthopaedics: OA with severe functional impairment (joint replacement); loose bodies, meniscal tear.
- Physiotherapy / OT: supervised exercise, joint protection, aids.
- DMARDs: monitor only under a current written shared-care agreement; methotrexate is contraindicated in pregnancy — plan pre-conception with rheumatology.
7Never reassure by
- Normal temperature, CRP or white cell count in a hot, swollen joint.
- Known gout or RA — infection can coexist; biologics mask inflammation.
- Negative RF/anti-CCP, normal CRP/ESR or normal X-ray in persistent synovitis.
- A normal urate during a flare.
- A normal early X-ray in septic arthritis or RA.
- Blaming infection or heart failure for new breathlessness on methotrexate.
8Safety-net — say it, then document it
999 / hospital “Call 999 if you feel very unwell with a hot, swollen joint. Go to hospital the same day if a joint becomes hot, swollen and very painful, even without a fever; if you are 50 or over with a new headache, jaw pain on chewing or any change in vision; or for new breathlessness, cough or fever on methotrexate.”
Same day: “Contact us the same day for mouth ulcers, severe nausea or unusual bruising on methotrexate, or new genital symptoms with reactive arthritis. If you have not heard about your rheumatology referral or appointment, or more joints are affected, contact us.”
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Joints counted; inflammatory vs mechanical recorded
Septic joint excluded, or sent the same day
Persistent synovitis referred without waiting for bloods
Review date and safety-net given and documented
Summary of the full Reasoning GP joint pain algorithm, which holds the examination, investigations, DMARD shared care, pregnancy, vaccination and evidence. Sources: NICE NG100 and QS33 (rheumatoid arthritis), NG219 (gout), NG226 (osteoarthritis), NG12 (suspected cancer), NG65 (spondyloarthritis), BSR GCA (2020) and csDMARD (2025) guidelines, BASHH, UKHSA Green Book and local formulary. Clinical reference — follow local pathways and check doses: NICE/SPC, BNF.