Reasoning GP · Algorithm · 1-page summary
Thigh pain
For: adults, children and young people with thigh pain, face to face, in hours or OOH. Not for: major trauma (emergency trauma pathway).
Core rule: most thigh pain is muscular, but clear the vascular, infective, compartment and bone-cancer emergencies — and a hip fracture in the older faller — first. A normal X-ray does not exclude bone malignancy or a stress fracture.
0Stop — call 999 now
- Acute limb ischaemia — sudden pain, pallor, pulselessness, paraesthesia, paralysis or marked coldness → 999 and notify the vascular service. Keep the limb flat, no compression; document time of onset; don't delay for bloods or imaging.
- Necrotising fasciitis / sepsis — pain out of proportion to skin signs, rapidly spreading erythema, toxicity, crepitus or skin necrosis → 999
- Suspected PE with haemodynamic compromise, syncope, severe hypoxia or marked deterioration → 999.
- Cauda equina — acute bladder/bowel dysfunction, saddle anaesthesia, or a progressive neurological deficit → 999 / emergency. Document neurological findings before referral.
1Triage by history — localise the origin
| Clue | Think → next |
|---|---|
| Older faller | Hip fracture → block 2 |
| Deep night bone pain | Sarcoma or metastasis → urgent X-ray |
| Walk → cramp → rest | Aorto-iliac PAD → ABPI ± arterial duplex |
| Drugs | Anticoagulant (haematoma) · statin (CK) · bisphosphonate (atypical fracture) |
2Screen — one row is enough
- Compartment syndrome: pain out of proportion, on passive stretch, tense → Immediate ED / orthopaedics. Pulses do not exclude it.
- Hip fracture: older faller, can't weight-bear, shortened rotated leg → Urgent ED with analgesia; 999 if unstable or unsafe to transfer.
- DVT (swelling, VTE risk, no PE features): two-level Wells → Same-day DVT pathway
- Bone or joint infection, pathological fracture → Same-day. Rest pain or tissue loss (CLTI) → Urgent vascular, often same-day phone.
- Bone sarcoma (NG12): X-ray suggests it → consider a Suspected cancer pathway. Child or young person with unexplained bone pain or swelling: consider X-ray ≤48 h; suggests sarcoma → consider referral ≤48 h
- Soft-tissue lump increasing in size (NG12): consider urgent USS ≤2 weeks (child or young person ≤48 h); suggestive or uncertain → consider referral. Never inject, biopsy or excise.
3Assess — both limbs, joint above and below
☐ Swelling, haematoma, wasting, mass ☐ Compartment tension, temperature, capillary refill ☐ Femoral, popliteal, pedal pulses both sides (Doppler if hard to feel) ☐ Hip, knee, lumbar spine ☐ L2–L4: knee extension power, knee jerk, femoral stretch ☐ Inguinal nodes, hernia
Targeted tests only: CK for diffuse myalgia or statin; HbA1c for amyotrophy; age ≥60 with persistent bone pain or unexplained fracture → offer myeloma bloods (NG12). Not: routine panels or PSA, imaging an improving strain, D-dimer when DVT is likely.
4Classify — only if the screen is negative
- Muscle strain / tear — sudden in sport; pain on resisted movement → graded loading.
- Meralgia paraesthetica — burning anterolateral patch, normal power and reflexes; weakness or reflex loss → rethink.
- L2–L4 radiculopathy — radicular pain down the front of the thigh → NICE NG59 pathway.
- Referred — pain on hip movement (hip OA, fracture), knee, hernia.
- Claudication — buttock/thigh cramp at a fixed distance, weak pulses or bruit → ABPI. Diabetic amyotrophy — painful quadriceps wasting.
- Uncertain or not improving — reassess for fracture, haematoma, tendon rupture, infection, DVT, malignancy or referred pain; do not escalate analgesia.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Strain: relative rest, early movement, progressive loading. No compression or elevation if fracture, compartment or vascular compromise is possible.
- Analgesia: paracetamol ± topical or short oral NSAID (caution: PAD, renal, elderly); opioids short term only. No automatic amitriptyline or gabapentin.
- Claudication: supervised exercise, stop smoking, BP and diabetes control; antiplatelet and statin once PAD is established.
- Meralgia: reassure, loosen tight belts, address weight. Amyotrophy: glycaemic control and physiotherapy; recovery takes months.
6Refer routinely
- Lifestyle-limiting claudication → vascular.
- Refractory strain, significant tear, tendon rupture, large haematoma, hip/knee pathology → orthopaedics / MSK. Femoral stress or atypical femoral fracture → Urgent
- Radiculopathy still limiting despite conservative care (no fixed week threshold) → spinal.
- Use the local DVT, vascular, MSK and sarcoma pathways.
7Never reassure by
- Present pulses — they do not exclude compartment syndrome.
- A normal X-ray — not sarcoma, stress fracture or hip fracture (then MRI; CT if MRI not within 24 h).
- A negative D-dimer when DVT is likely — go straight to ultrasound.
- Thigh circumference — it documents asymmetry, it does not diagnose DVT.
- Mild skin signs when pain is out of proportion.
- A "strain" label that is not improving.
8Safety-net — say it, then document it
999 “Leg swelling with breathlessness, chest pain, fainting or coughing blood; a leg that is suddenly cold, pale, numb or weak; new leg weakness or numbness, bladder or bowel trouble, or numbness between the legs.” Immediate ED “Severe pain with a tense, swollen thigh; spreading redness, fever or rapidly worsening pain (999 if unwell); unable to weight-bear after a fall.”
Same day “New or increasing swelling of the thigh or calf.” ≤1 week “Worsening bone pain, a new or growing lump, or weight loss” (≤48 h for a child or young person). Record diagnosis, red flags checked, plan and review interval.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Both limbs, pulses, compartments, hip, knee, spine and L2–L4 examined
Wells done if swollen; tests targeted, not routine
Named cause or uncertainty stated; review interval set
Safety-net given and documented
Summary of the full Reasoning GP thigh pain algorithm, which holds the history, examination, investigations and evidence. Sources: NICE NG12 (updated April 2026), NG158, CG147, CG124, NG59; MHRA bisphosphonate atypical femoral fracture guidance. Clinical reference — follow local pathways and check doses: NICE/SPC, BNF.