Kanavel's four cardinal signs of flexor tenosynovitis are one of the most important surgical emergency frameworks in hand surgery — they must be memorised by every GP who examines hands: (1) Finger held in slight flexion at rest (the position of minimum tenosynovial tension); (2) Uniform fusiform swelling of the entire finger ('sausage finger' — the swelling follows the tendon sheath from distal palm to fingertip); (3) Intense pain on passive extension of the finger (as the inflamed sheath is stretched); (4) Tenderness along the course of the flexor tendon sheath on palpation (palmar surface from A1 pulley to fingertip). All four signs present = pyogenic flexor tenosynovitis until proved otherwise. Three signs present in an unwell patient with a wound or puncture history: same-day hand surgery referral. The stakes: the flexor tendon sheath is a closed space with poor blood supply. Pus under pressure destroys the tendon within 24-48 hours, causing permanent loss of finger flexion. Early washout (within 24h) restores normal function in the majority; delayed surgery (>48h) results in permanent disability in approximately 50% of cases.

Dupuytren's contracture management has been transformed by collagenase clostridium histolyticum (Xiapex) — GPs should know the referral criteria for this condition, which affects approximately 3-4% of the UK population (higher in men, older age, Northern European descent, diabetes, alcohol, epilepsy/phenobarbitone). The clinical rule for referral: the 'tabletop test' — if the patient cannot place their hand flat on a table (palm down, fingers extended), referral to hand surgery is indicated. The MCP joint contracture at ≥30° is the standard threshold for intervention (either Xiapex injection or surgical fasciectomy). Xiapex: collagenase injected directly into the Dupuytren cord, followed the next day by manipulation to rupture the cord — approximately 60% achieve ≥50% correction of MCP contracture; lower efficacy for PIP contractures. Surgical fasciotomy/fasciectomy: higher correction rate, more invasive. GPs who observe progressive Dupuytren's contracture without referral when the patient has functional impairment are missing an intervention window.

The joint aspiration and synovial fluid analysis is the single most important investigation in distinguishing septic arthritis from crystal arthropathy (gout or pseudogout) in an acutely swollen hot joint — and GPs cannot usually perform this in primary care, making prompt same-day hospital assessment essential. The synovial fluid findings: septic arthritis: turbid, cloudy, WBC >50,000/mm³ (often >100,000), predominantly polymorphs, glucose low, lactate high, organisms on gram stain in approximately 50-70%. Gout: needle-shaped negatively birefringent sodium urate crystals under polarised light microscopy. CPPD (pseudogout): positively birefringent rhomboid calcium pyrophosphate crystals. The critical overlap: septic arthritis and crystal arthropathy can coexist in the same joint — a crystal-positive fluid does not exclude concurrent infection. Any acutely hot swollen finger joint must be aspirated and cultured before antibiotics are started (or immediately after if delay is unavoidable).

The anti-CCP antibody (anti-cyclic citrullinated peptide IgG) is the most specific blood test for rheumatoid arthritis, with specificity of approximately 96% — a positive anti-CCP in a patient with finger joint synovitis (soft warm swelling of MCP or PIP joints) is a strong indication for urgent rheumatology referral because: (1) anti-CCP positivity predicts a more aggressive erosive disease course; (2) DMARD therapy (methotrexate as anchor drug) started within 3-6 months of symptom onset achieves significantly better long-term outcomes than delayed treatment — this is the 'window of opportunity' in RA treatment; and (3) early treatment can prevent the joint destruction, deformity, and disability that characterised RA before DMARDs. The practical primary care standard: any patient with symmetrical small joint synovitis (especially MCP + PIP sparing DIP, morning stiffness >1h) should have anti-CCP + RF + ESR/CRP requested at the same consultation, with a follow-up appointment in 2-3 weeks to review results and consider rheumatology referral if positive.

The corticosteroid injection for trigger finger is a primary care procedure with strong evidence and high success rates — a systematic review shows that a single corticosteroid injection achieves resolution in approximately 60-70% of trigger fingers at 1 year (Quinnell grade 2), with a second injection adding approximately 15-20% further resolution. The technique: with the patient's palm up, identify the A1 pulley (proximal flexor crease, directly over the MCP joint). Insert a 23-25G needle at 45° pointing proximally into the tendon sheath at the A1 pulley level (the needle should be in the sheath, not in the tendon — if excessive resistance is felt, reposition before injecting). Inject triamcinolone acetonide 40 mg/mL 0.5 mL with 0.5 mL lidocaine 1% (for immediate analgesia). Post-injection: rest finger for 2-3 days, then normal activity. Review at 6-8 weeks — if partial response, consider second injection. Diabetic patients: warn that a single finger injection can cause blood sugar elevation for 3-5 days.

The colchicine prophylaxis strategy when initiating allopurinol is essential for preventing the well-known phenomenon of mobilisation gout — when urate-lowering therapy begins, the rapid fall in serum urate mobilises monosodium urate crystals from existing tissue deposits, triggering inflammatory attacks. Without prophylaxis, approximately 70-80% of patients experience gout flares in the first 3-6 months of allopurinol treatment — these flares are so distressing that many patients stop allopurinol, incorrectly attributing the flares to the drug itself. The prevention strategy: colchicine 500 mcg OD (or BD if tolerating well, to maximum 500 mcg BD) continued for the first 3-6 months of allopurinol therapy. NSAIDs can also be used for prophylaxis but are poorly tolerated in the long-term. The critical prescribing communication: 'Allopurinol is working correctly even if you get a gout attack in the first few months — do not stop the allopurinol. The colchicine is to protect you during this initial period.'

The methotrexate monitoring protocol in primary care is a shared care responsibility that requires systematic organisation — the BSR/BHPR recommendations specify that in the shared care phase (after rheumatology stabilisation), GPs should monitor: FBC (neutropenia, macrocytosis, thrombocytopenia), LFTs (hepatotoxicity — risk increased with alcohol), albumin (hypoalbuminaemia), U&Es (MTX is renally cleared — eGFR drop increases toxicity) at 3-monthly intervals. The MHRA yellow card system should be used to report serious adverse effects. The action thresholds requiring MTX dose reduction or suspension: WBC <3.5 × 10⁹/L, neutrophils <2 × 10⁹/L, platelets <150 × 10⁹/L, ALT or AST >twice the upper limit of normal, albumin <30 g/L, or eGFR <30 mL/min/1.73m². GPs must have a clear MTX monitoring template in the EMIS/SystmOne record — a patient on MTX without 3-monthly bloods in primary care is a clinical governance concern.

The HAVS (Hand-Arm Vibration Syndrome) is an occupationally prescribed disease that GPs can diagnose and facilitate compensation claims for — it affects workers using vibrating hand-held tools (pneumatic drills, grinders, chainsaws, road breakers) and causes: Raynaud's phenomenon of the fingers (vibration white finger — a specific occupational form of Raynaud's), sensorineural hand-arm vibration (SNHAV — peripheral neuropathy causing tingling, numbness, reduced grip), and musculoskeletal effects (carpal tunnel syndrome, reduced dexterity). It is classified under COSHH and is a Prescribed Disease under the Industrial Injuries Disablement Benefit scheme (PD A11 for vibration white finger; PD A12 for SNHAV). GPs who see construction or manufacturing workers with Raynaud's or neuropathic hand symptoms should take a detailed occupational history (years of vibration tool use, daily exposure hours) and refer to the occupational health physician for formal HAVS assessment and disease notification.

The trigger finger 'safe splinting' principle for mallet finger must be communicated precisely to patients — failure to maintain the DIP joint in continuous full extension for 6-8 weeks is the most common reason for mallet finger treatment failure. The DIP joint must NEVER be allowed to flex during the splinting period, not even for a moment to wash or refit the splint. If the DIP flexes even once during the treatment course, the healing extensor tendon re-ruptures and the 6-8 week clock must restart. The correct patient instruction: 'When you need to clean under the splint, hold the finger completely straight with your other hand before removing the splint, then slide the splint off — keeping the finger extended throughout. Clean underneath it while keeping the finger straight, then slide the splint back on.' A patient who removes a mallet splint without understanding this principle will invariably re-rupture the tendon. Document this instruction in the clinical notes.