Foot Pain
Pain in the foot is difficult for patients to ignore and so will often present with a relatively short history. Local causes predominate, but remember to think further afield: Referral through S1 (lateral border of the foot) and L5 (dorsum of the foot to the big toe) nerve roots may occur. Ankle pain is not considered here.
Differential diagnosis
Common Diagnoses
- Gout
- Verruca
- Bunion/Hallux Valgus
- Infected Ingrowing Toenail (IGTN)
- Plantar Fasciitis
Occasional Diagnoses
- Morton’s Neuroma
- Metatarsalgia
- Arthritis (Osteo and Rheumatoid)
- Achilles Tendonitis/Bursitis
- Oedema
- Foreign Body
Rare Diagnoses
- March Fracture
- Sever’s Disease (Apophysitis of the Calcaneus), Usually a Problem of Adolescence
- Osteochondritis: Navicular = Köhler’s Disease; Head of Second or Third Metatarsal = Freiberg’s Disease
- Osteomyelitis and Septic Arthritis
- Erythromelalgia and Painful Polyneuropathy
- Ischaemia
Ready reckoner
Key distinguishing features of the most common diagnoses
| Gout | Verruca | Bunion | IGTN | Plantar Fasciitis | |
|---|---|---|---|---|---|
| Forefoot Pain | Yes | Possible | Yes | Yes | No |
| Very Tender Joint(s) | Yes | No | Possible | No | No |
| Pain at Rest | Yes | No | No | Possible | No |
| Tender Heel | No | Possible | No | No | Yes |
| Sudden Onset | Yes | No | No | Possible | Possible |
Possible investigations
Likely: None.
Possible: Urinalysis, FBC, ESR/CRP, rheumatoid factor/anti-CCP antibodies, uric acid, X-ray.
Small Print: Bone scan, angiography.
- Urinalysis may reveal glycosuria in previously undiagnosed diabetic with neuropathy (suspicion of neuropathy may in itself require further investigations).
- FBC/ESR/CRP: Raised WCC and ESR/CRP in infection and severe inflammation.
- Rheumatoid factor: Of prognostic help if foot pain is part of clinical diagnosis of rheumatoid arthritis (consider anti-CCP antibodies if negative).
- Uric acid: If gout suspected, especially with recurrent attacks and if considering prophylaxis.
- X-ray useful if suspect possible arthritis, osteomyelitis, march fracture, osteochondritis, radio-opaque foreign body. If clinical suspicion high and X-ray unhelpful, bone scan may be more useful.
- Angiography: If ischaemic foot with rest pain.
Top Tips
- The vast majority of causes are obvious from the history or from a cursory examination. The harder you have to think, the more likely that there may be an obscure cause requiring investigation.
- It can be difficult to distinguish gout from a severely inflamed bunion. With gout, the patient may have had previous episodes, the onset tends to be sudden, the joint is extremely tender and joint movements are very limited.
- Important pointers can be picked up in the history, especially for some of the less common causes. Thus, Morton’s neuroma causes a sharp pain often radiating to the third and fourth toes, relieved by removing the shoe; plantar fasciitis is described as ‘walking on a pebble’, especially after resting; and a march fracture results in a pain which initially comes on predictably with exercise and which then becomes continuous, with local bony tenderness and possibly a lump.
Red Flags
- If a known arteriopath complains of pain in the ball of the foot disturbing sleep then the diagnosis is probably critical ischaemia. Refer urgently.
- Fever and systemic illness with localised extreme bone pain and signs of local infection is acute osteomyelitis or septic arthritis until proved otherwise. Admit.
- Pain with no obvious signs – particularly tenderness – in the foot suggests ischaemia, neuropathy or an L5/S1 nerve root lesion.
- If no cause is evident but the patient has very localised sole tenderness away from the heel, consider a foreign body.