The lower leg concentrates several time-critical diagnoses: a DVT that can embolise to the lungs, an acutely ischaemic limb whose viability depends on occlusion site, collaterals and neurological deficit, a calf compartment syndrome, and necrotising fasciitis. Each is separated from benign leg pain by a single discriminator — unilateral swelling with VTE risk, the 6 Ps, pain out of proportion, or systemic toxicity — and each is acted on before, not after, imaging.
NICE NG12 places bone sarcoma on the primary-care radar, and the tibia is one of the commonest sites of osteosarcoma in young people. Persistent deep bone pain, particularly at night, or a bony swelling warrants an urgent X-ray; an X-ray suggesting sarcoma should prompt NICE's "consider" recommendations — a suspected cancer pathway referral in adults and a very urgent referral for specialist assessment in children and young people (whose X-ray NICE advises considering very urgently, within 48 hours), and persisting suspicion with a normal film still needs repeat imaging or referral.
The two claudication histories are the highest-yield discriminator in leg pain. Vascular claudication is brought on by a fixed walking distance and relieved by simply stopping; neurogenic claudication (lumbar spinal stenosis) is brought on by standing and walking and relieved by flexion — sitting, leaning on a trolley, walking uphill — and the two lead to completely different investigations and specialists.
A clear VTE risk profile changes the pre-test probability of DVT enough to drive the whole pathway, while a cardiovascular risk profile reframes calf claudication as a marker of systemic atherosclerosis whose main threat is myocardial infarction and stroke, not the leg itself.
A leg examination is incomplete without the pulses, the L5/S1 neurology and the spine, because the three commonest serious causes — ischaemia, sciatica/cauda equina and DVT — declare themselves there rather than in the painful muscle. A single absent pulse or a focal motor deficit redirects the entire work-up.
Simple bedside tests carry a lot of weight here: the Simmonds calf-squeeze rapidly identifies an Achilles rupture that is otherwise easy to miss, calf circumference quantifies the asymmetry of a DVT, and capillary refill and the Buerger test grade arterial insufficiency without any equipment.
Sorting the differential by tissue keeps the dangerous and the trivial side by side — a ruptured Baker’s cyst and a DVT both present as a swollen painful calf — if DVT is clinically suspected, follow the DVT pathway; do not use ultrasound solely to confirm a Baker’s cyst before DVT is excluded. The framework prevents the common error of treating a DVT as a strain or a strain as a DVT.
Restless legs and nocturnal cramps are common, benign and frequently missed in the rush to exclude vascular disease; recognising their characteristic histories (an urge to move at rest, relieved by movement; sudden painful nocturnal contractions) avoids unnecessary investigation and gives the patient an explanation and a management plan.
Each investigation answers a specific question raised by the history: a Wells score and ultrasound for venous disease, an ABPI for arterial disease, an X-ray then MRI for bone, and an MRI for a neurological deficit or spinal stenosis. Ordering tests by hypothesis rather than reflex avoids both missed diagnoses and incidental findings that mislead.
Two rules prevent the commonest errors: a high clinical probability of DVT goes straight to ultrasound because a D-dimer cannot exclude it (a D-dimer follows if the scan is negative), and early uncomplicated sciatica is not imaged because most settles within weeks and an MRI rarely changes early management — imaging is reserved for red flags, a progressive or significant deficit, failure to improve, or a planned intervention.
The referral map follows directly from the red flags: vascular, infective and neurological emergencies bypass investigation, while the two NG12 sarcoma routes (bone via X-ray, then consider a suspected cancer pathway referral — X-ray and specialist assessment within 48 hours for children and young people; soft tissue via urgent ultrasound — within 48 hours for children and young people — then consider a suspected cancer pathway referral if it suggests sarcoma) are the cancer safety net that primary care must apply to any unexplained limb lump or persistent bone pain.
Timing matters for the common conditions too: most sciatica is managed in primary care and referred only when it has not improved despite an appropriate trial of conservative care, or for a deficit, whereas a suspected Achilles rupture or symptomatic varicose veins with skin change have their own defined, more urgent referral routes that are easy to overlook.
Next steps: see Deep vein thrombosis · Peripheral arterial disease · Sciatica · Restless legs syndrome · Leg cramps
The mainstays are active, not passive: graded loading for calf injury, staying active with simple analgesia for sciatica (NICE NG59 advises not offering gabapentinoids, oral corticosteroids or benzodiazepines for sciatica, or opioids for chronic sciatica), and a supervised exercise programme plus cardiovascular risk control for claudication. Each has better outcomes than rest and escalating medication.
Two safety rules bracket the treatment: never compress a leg without first excluding significant arterial disease (ABPI or equivalent vascular assessment), because compression of an ischaemic limb causes tissue loss; and never quietly escalate opioids for sciatica, because the deterioration that matters (a progressive deficit or cauda equina) is missed if the consultation becomes a prescription rather than a re-examination.
Because the leg is so often a window onto systemic disease, the lifestyle package does double duty — the cardiovascular risk-factor work that eases claudication is the same work that prevents the patient’s next coronary or cerebral event, which is the real prognosis-changer in peripheral arterial disease.
For the benign but troublesome diagnoses — cramps, restless legs, venous insufficiency — simple, specific self-management (stretching and hydration, iron repletion, elevation and compression) resolves or controls symptoms for most patients and prevents both unnecessary investigation and progression to complications such as venous ulceration.
Concrete, symptom-level safety-netting is what makes a benign label safe in the leg, where the dangerous diagnoses (DVT/PE, ischaemia, necrotising infection, cauda equina) can evolve over hours. The patient should leave able to name the specific changes that mean same-day or 999 review rather than holding a vague instruction to return if no better.
Pairing the advice with a planned review interval turns it into active follow-up: sciatica and calf strains that do not follow their expected recovery curve are a cue to re-open the differential — re-examine the neurology, reconsider stress fracture or sarcoma, recheck the vasculature — instead of escalating analgesia on an unconfirmed diagnosis.