Differentials
| System |
What might it be? |
What might I find? |
|
| Peripheral Arterial |
Intermittent Claudication |
RF: ↑age, male sex, smoking, obesity, hypertension, diabetes, family history.
Cramping lower limb pain during exertion, relieved by rest, due to ischaemia. May be unilateral or bilateral. Exertion tolerance indicates disease severity. Ankle-brachial pressure index (ABPI) will be reduced at around 0.6-0.9. |
|
|
Chronic Limb-threatening Ischaemia |
RF: as for intermittent claudication. Advanced peripheral arterial disease.
Development of pain at rest instead of solely exertional, worst at night. Ulcers. ABPI 0.3-0.6. |
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|
Acute Limb Ischaemia |
RF: as for intermittent claudication.
Acute development (<2/52) of limb ischaemia usually secondary to thrombus. 6 Ps: pale, pulseless, paraesthesia, pallor, painful, perishingly cold. |
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|
Buerger Disease |
RF: young, male, smoker (else no other CVD risk factors).
Discolouration and pain to peripheries, worse at night. Angiography required. |
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|
Arterial Ulcer |
RF: as for intermittent claudication.
Painful distal ulcer e.g., toes. Minimal bleeding, punched out, deep, small. |
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| Peripheral Venous |
Deep Vein Thrombosis (DVT) |
RF: cancer, pregnancy, surgery, hormonal tx, long-haul travel, immobility.
Unilateral hot swollen red and tender calf. Affected calf measures >3 cm larger. |
|
|
Post-thrombotic syndrome |
Presentation as for chronic venous insufficiency caused by previous DVT.
Chronic leg pain, heaviness, skin discolouration. May present years after DVT. |
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|
Varicose Veins |
RF: age, pregnancy, obesity, prolonged standing.
May be asymptomatic. Heavy, aching, dragging sensation uni/bilateral legs. Itching or burning, cramping pain, restless legs. May be associated with chronic venous insufficiency. |
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|
Chronic Venous Insufficiency |
RF: ↑age, associated obesity, immobility, venous disease e.g., varicose veins.
Bilateral swelling & associated skin changes in gaiter region, can be painful. |
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| Musculoskeletal |
Spinal Stenosis |
RF: ↑age, degenerative changes, herniated discs, spinal #, spondylolisthesis.
Lower back & leg pain/weakness/numbness on standing, walking. Improved by rest. Improved bending forwards and sitting. ABPI will be normal, pulses present. |
|
|
Sciatica |
RF: herniated disc, spinal stenosis, spondylolisthesis.
Unilateral pain from buttock radiating down back thigh to below knee. Associated weakness, numbness and paraesthesia. |
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|
Compartment Syndrome |
RF: recent acute injury: fracture or crush injury.
5Ps: pain (disproportionate), paraesthesia, pale, paralysis, pressure rise. Pulses normal. Disproportionate pain not responding to analgesia. |
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| Miscellaneous |
Peripheral Neuropathy |
RF: alcohol excess, B12 deficiency, cancer, CKD, diabetes, drugs, vasculitis.
Sensory (and motor) loss in peripheries e.g.,. hands & feet in a ‘glove & stocking distribution’. Can cause burning pain, worse at night. |
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|
Cellultis |
RF: skin break, diabetes, obesity, immunocompromise, venous insufficiency.
Unilateral acute redness, swelling, heat and pain to skin of lower leg. May be associated with systemic upset e.g., pyrexia or source e.g., wound. |
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Checklist
| Preparation | Wash – Name – Explain | |
| Presenting Complaint | Open question to establish reason for presentation | |
| Allow patient time to talk uninterrupted | ||
| History of Presenting Complaint | Site | |
| Onset | ||
| Character | ||
| Radiation | ||
| Associated symptoms | ||
| Timing | ||
| Exacerbating/relieving factors | ||
| Severity | ||
| System-specific | Colour change | |
| Leg swelling | ||
| Ulcers | ||
| Exercise tolerance | ||
| Relevant Systems Review | Musculoskeletal | |
| Neurological | ||
| ICE | What do you think is going on? | |
| Is there anything that is worrying you? | ||
| What were you hoping we would do today? | ||
| Past Medical History | Past medical history | |
| Past surgical history | ||
| Drug History | Prescribed medication | |
| Over the counter medication | ||
| Drug allergies | ||
| Social History | Smoking | |
| Alcohol | ||
| Recreational drugs | ||
| Work | ||
| Driving | ||
| Who is at home? | ||
| Sick contacts | ||
| Forgeign travel | ||
| Family History | Does anyone in the family have cardiovascular disease? | |
| Do any other health conditions run in the family? | ||
| Comm. Skills | Establish rapport | |
| Use open and closed questions appropriately | ||
| Structured history taking | ||
| Pick up on cues | ||
| Rule in/out differential diagnoses | ||
| Summarise succinctly |
Explanation
Preparation
Wash, name, explain:
- Wash your hands
- Introduce yourself by name and role
- Check the patient’s name and date of birth
- Explain the task and get consent
“I have been asked to speak to you about the pain you have been experiencing in your leg(s). I will ask you some questions to try to determine what might be causing it. Does that sound all right?”
Presenting Complaint
Begin with an open question to establish the patient’s reason for seeking medical attention, for example “Could you tell me about what has been going on?”
Try to let the patient speak for 30-60 seconds without interruption. This is referred to as the ‘golden minute’ and can provide valuable information about why the patient has sought medical attention as well as cues surrounding their ideas, concerns, and expectations (ICE) to explore later in the consultation.
History of Presenting Complaint
Next, you need to gather more specific information about the patient’s presenting complaint to establish the differential diagnosis. You can use a mixture of open and closed questions.
Examples of an open question here include: “How would you describe the pain?” or “Have you noticed any other symptoms alongside the leg pain?”. Examples of closed questions include: “Is the pain constant or intermittent?” or “Does the pain come on with exertion?”
When taking a pain history, it is useful to use the SOCRATES mnemonic to guide your questioning:
- Site – where in the leg(s) is the pain? Is it buttock and thigh pain (common in spinal stenosis or sciatica), or more distal pain in the lower thighs or calves (more common in intermittent claudication)? Is the pain unilateral or bilateral? Conditions like cellulitis or a DVT are very unlikely to be bilateral, whereas bilateral sciatica is a red flag for cauda equina syndrome.
- Onset – when did the pain start, and what happened? How long has it been going on? Sudden onset lower limb pain may indicate a thrombotic cause e.g., deep vein thrombosis (DVT) or acute limb ischaemia secondary to an arterial thrombus. Severe pain following a crush injury or fracture raises a red flag for compartment syndrome.
- Character – what type of pain is the patient experiencing? What words would they use to describe it? E.g., sharp, cramping, aching, shooting pain.
- Radiation – does the pain travel anywhere else from the main site? E.g., sciatica pain typically shoots from the lower back/buttock down the back of the affected leg.
- Associated symptoms – does the patient experience any other symptoms alongside the leg pain? Associated skin colour changes and ulceration may make you think of peripheral arterial disease, whereas leg swelling, chest pain, and breathlessness would make you concerned about a DVT +/- pulmonary embolism.
- Timing – what is the time course of the pain? How long does it last? Is it constant or intermittent? Chronic limb-threatening ischaemia pain is worse at night due to loss of gravitational circulation assistance.
- Exacerbating and relieving factors – what makes the pain better? Does anything make the pain worse? Pain brought on by exertion may indicate intermittent claudication or spinal stenosis; both improve with rest and the latter would also improve with sitting forwards.
- Severity – on a scale of 0-10, with 0 being no pain and 10 being the worst pain imaginable, how would the patient rate the severity of their pain? Severe pain that is disproportionate to the appearance of the limb may raise a red flag for compartment syndrome.
System-specific History
After gathering further information about the lower limb pain, you need to ask about any relevant system-specific symptoms. In the case of leg pain, the primary system in question is the peripheral vascular system. Try to consider symptoms that may present alongside lower limb pain.
It is important not only to ask these questions but also to understand why the patient’s answers are important to narrow down the differential diagnosis.
For example, the presence of pallor and a punched-out, painful, distal ulcer alongside leg pain may lead you to consider peripheral arterial disease in the differential. However, the absence of pallor, along with haemosiderin deposits and a shallow, sloughy ulcer with achy lower limb pain in the gaiter region, would strongly suggest chronic venous insufficiency.
System-specific questions to ask include but are not limited to:
- Colour change – has the patient noticed any changes in the colour of the limb? E.g., pallor, rubor, erythema, or haemosiderin deposits.
- Leg swelling – unilateral painful leg swelling may occur in DVT, cellulitis, post-thrombotic syndrome, or compartment syndrome. Bilateral swelling is associated with conditions including chronic venous insufficiency.
- Ulcers – arterial ulcers are typically punched out, painful, small, peripheral, deep, and bleed minimally. Venous ulcers: tend to occur in the gaiter region and are sloughy, less painful, superficial, large, and have sloped or irregular edges.
- Exercise tolerance – is the patient’s activity or exercise limited by their symptoms, e.g., intermittent claudication or spinal stenosis? How far can they walk before getting pain? Has this changed over time? Do they now experience pain at rest?
Relevant Systems Review
A systems review is a useful tool to ensure no important information from the history has been missed. However, it is essential to determine which systems to review to ensure your questions remain relevant to the presenting complaint.
Relevant systems to review when taking a history of lower limb pain include:
- Musculoskeletal (MSK) – musculoskeletal conditions are some of the key differentials of lower limb pain. Factors that may make you consider MSK causes include: pain radiating down from the lower back/buttocks, neurological symptoms e.g., weakness, numbness, or paraesthesia, or pain following injury or trauma.
- Neurological – neuropathic pain from peripheral neuropathy can cause significant lower limb pain. Causes of peripheral neuropathy include diabetes, vitamin deficiency (e.g., B12), chronic alcohol use, and Charcot-Marie-Tooth disease.
Ideas, Concerns & Expectations (ICE)
Using the ICE mnemonic, you can gather information about how the patient feels about their symptoms, whether they have a specific worry or concern, and how they hope to move forward after seeking medical attention. Try to develop your own style of asking about ICE that works for you; some examples are included below:
- Ideas – “Do you have any thoughts about what might be going on?” “What do you think might be causing this pain?”
- Concerns – “Is there anything worrying you about this pain?” ‘Have you read or Googled anything about your symptoms that has caused you concern?”
- Expectations – “Was there anything specifically you were hoping we’d do today?” “Do you have any ideas of what might happen next?”
Past Medical History
Obtain information about any previous or existing health conditions the patient may have. Note when an existing condition may be relevant to the presenting complaint of lower limb pain, e.g., the patient has ischaemic heart disease (IHD) or has had a transient ischaemic attack (TIA). Both conditions are associated with atherosclerosis and increase the likelihood of co-existing peripheral arterial disease. Patients with diabetes and poor glycaemic control are more likely to develop diabetic neuropathy.
Ask about any previous surgery, particularly if it will help to rule in or out differential diagnoses, e.g., the patient has presented with acute lower limb pain and swelling and had major surgery a week ago (increased venous thromboembolism risk).
Drug History
Ask the patient about any regular medication they take, asking specifically about those that the patient may not think to mention, including over the counter medications, herbal or alternative remedies, contraception, HRT, and injections like vitamin B12. Check whether the patient is compliant with their medication and taking it as prescribed.
Try to consider whether the information you are given could be relevant to the differential diagnosis.
Remember to ask about drug allergies and clarify any reported symptoms to distinguish between a true allergy and an intolerance.
Social History
This is the opportunity to learn more about the patient beyond their presenting complaint.
- Who do they live with? Do they have a social support network? e.g., if receiving a debilitating diagnosis, or if mobility declines help with personal care and activities of daily living is required.
- Do they work? Are they able to working with their current symptoms? Does their job require adaptations? e.g., physically demanding work may need to be adapted for exertional symptoms. Is their job active or sedentary? Could they increase physical activity on their commute to work, e.g., walk or cycle to work?
- Do they drive? Does their condition affect their ability to drive or attend appointments? Do their symptoms occur while driving, e.g., claudication. Do they need to inform the DVLA? All licence holders must notify the DVLA if they have peripheral neuropathy, whereas only Group 2 licence holders are required to report peripheral arterial disease.
- Have they had contact with someone with similar symptoms?
- Have they recently returned from travelling abroad?
- Do they smoke? Smoking increases risk of peripheral vascular disease and will worsen existing disease. Patients should be encouraged to cut down or stop whenever possible.
- Do they drink alcohol? Alcohol increases general cardiovascular risk.
- Do they use recreational drugs?
Try to think about the relevance of the information you are given. E.g., a young patient with no cardiovascular risk factors presents with limb pain and discolouration which is worse at night; if they turn out to be a heavy smoker, a diagnosis such as Buerger disease appears in the differential which may influence your investigation and management plan.
Family History
Does anyone in the family have peripheral vascular disease? A family history of PAD is a non–modifiable risk factor for the patient developing the same condition.
Do any other health conditions run in the family, e.g., inherited thrombophilia, which may increase risk of developing DVT?
Finishing
Thank the patient and wash your hands. Consider your differential diagnosis and how you might narrow this down further by way of examination, bedside tests or further investigation/imaging.
Last updated Mar 2025
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