Trokos

Special tests library › Red flags

Ankle and foot red flags

What you cannot afford to miss in ankle and foot pain, before any special test.

Most ankle and foot pain is musculoskeletal. These are the conditions that are not, or that need referral before treatment, with the features that point to each. Every row carries its source, listed at the foot of the page.

Use with your local protocols. Referral pathways, and how urgently to act, differ between health services and countries: where your local protocol or current guideline differs, follow it. Never delay emergency care to check a protocol.

Can’t missWhat points to it
Fracture after an ankle or midfoot injury1The Ottawa ankle and foot rules are applied. Bone tenderness at the posterior edge or tip of either malleolus (lower 6 cm), at the navicular or at the base of the fifth metatarsal, or inability to take four steps both at the time of injury and at assessment, indicates the need for an X-ray. The rules do not apply when the patient cannot reliably report tenderness (intoxication, head injury, multiple injuries, neuropathy). An open wound over a suspected fracture or gross deformity is an emergency.
Growth-plate fracture in a child2In a child, tenderness directly over the lateral malleolus (the distal fibular growth plate) rather than over the lateral ligaments suggests a growth-plate fracture, which is often misdiagnosed as a sprain. X-rays should be obtained, although they may appear normal.
Lisfranc injury3,4Features include midfoot pain and swelling after an axial load or twisting injury, bruising on the plantar surface of the midfoot, dorsal midfoot tenderness, or inability to rise onto the toes. A substantial minority of these injuries are missed on non-weight-bearing X-rays, and a missed injury carries a risk of arthritis and persistent instability. The patient should be referred for weight-bearing imaging.
Stress fracture at a high-risk site5,6Features include gradual-onset dorsal midfoot pain in a running or jumping athlete (navicular), or aching and point tenderness just distal to the base of the fifth metatarsal (proximal shaft) without a clear injury. Both sites heal poorly. X-rays are often normal in the early stages, particularly at the navicular. The aggravating load should be stopped and the patient referred for CT or MRI; the injury should not be managed as a sprain.
Compartment syndrome or acute ischaemia7,8Features include disproportionate pain, worse with passive stretch of the toes, in a tense, swollen compartment; or a pale, cold or numb foot after trauma, dislocation, or the application of a new cast or strapping. Pulses are often present early. Emergency referral is required, because tissue damage begins within hours.
Achilles tendon rupture9The patient describes a sudden pop or a sensation of being kicked in the back of the heel. Up to a quarter of ruptures are missed at first presentation, partly because many patients can still walk and plantarflex the foot. The Thompson test should be performed. If the history is consistent, orthopaedic or emergency department assessment should be arranged the same or next day, even when one sign is normal. The injury should not be treated as a calf strain.
Deep vein thrombosis10Features include unilateral calf or ankle swelling, warmth and tenderness, particularly after immobilisation, surgery or travel. The patient requires same-day medical assessment and should not be treated for a calf strain.
Septic arthritis11,12Features include a hot, swollen, acutely painful ankle or subtalar joint with restricted movement, particularly in a patient who is diabetic or immunosuppressed. The classic triad with fever is often absent. Same-day medical assessment is required; the diagnosis is made by joint aspiration.
The diabetic foot13,14,15A warm, red, swollen foot with unexpectedly little pain in a person with diabetes should be regarded as Charcot neuroarthropathy until proven otherwise; it is often mistaken for a sprain, cellulitis or gout. Same-day medical assessment is required, and until then the patient should keep weight off the foot, because unprotected walking can lead to fracture and collapse. Spreading redness around a wound with fever or systemic illness requires urgent medical care. With loss of protective sensation, fractures and infection can be nearly painless, so the threshold for referral on any other finding in this list should be lower.
Tumour16,17Features include progressive, unremitting pain that is worse at night and not relieved by rest, an enlarging mass, or pain that persists through months of treatment for a presumed overuse injury. The patient should be referred promptly for medical assessment and imaging.

A red flag raises suspicion; it does not make the diagnosis, and its absence does not rule the condition out. The table is not a complete list of every serious condition, and it is not a clinical protocol. When a red flag is present, act on the referral advice in the row, in line with your local protocols. This page is for registered health practitioners and students and is not clinical advice for patients; see the terms of use.

Last checked against the cited sources: 15 October 2026.

Then the tests: Ankle and foot special tests, with sensitivity, specificity and likelihood ratios.

Get the book for spotting a high ankle sprain, and knowing when the Achilles is torn

This table opens the chapter ‘The ankle and foot’ in Rule It In, Rule It Out. The book then works through the questions that matter in this region, with the published figures for each test and how to read them.

Coming in late 2026 as a PDF and a paperback. Join the list to hear when it's out

Sources

  1. Bachmann LM, Kolb E, Koller MT, Steurer J, ter Riet G. Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. BMJ. 2003;326(7386):417. Link
  2. Distal tibia and/or fibula physeal fractures. Clinical Practice Guidelines, The Royal Children's Hospital Melbourne, Emergency Department. Link
  3. Burroughs KE, Reimer CD, Fields KB. Lisfranc injury of the foot: a commonly missed diagnosis. Am Fam Physician. 1998;58(1):118–124. Link
  4. Ross G, Cronin R, Hauzenblas J, Juliano P. Plantar ecchymosis sign: a clinical aid to diagnosis of occult Lisfranc tarsometatarsal injuries. J Orthop Trauma. 1996;10(2):119–122. Link
  5. Coris EE, Lombardo JA. Tarsal navicular stress fractures. Am Fam Physician. 2003;67(1):85–90. Link
  6. Smidt KP, Massey P. 5th Metatarsal Fracture. StatPearls Publishing; updated May 29, 2023. Link
  7. Frink M, Hildebrand F, Krettek C, Brand J, Hankemeier S. Compartment syndrome of the lower leg and foot. Clin Orthop Relat Res. 2010;468(4):940–950. Link
  8. The '6 Ps' — Acute Limb Ischaemia. RCEMLearning. Link
  9. Gravlee JR, Hatch RL, Galea AM. Achilles tendon rupture: a challenging diagnosis. J Am Board Fam Pract. 2000;13(5):371–373. Link
  10. Wells PS, Anderson DR, Rodger M, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003;349(13):1227–1235. Link
  11. Earwood JS, Walker TR, Sue GJC. Septic arthritis: diagnosis and treatment. Am Fam Physician. 2021;104(6):589–597. Link
  12. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis? JAMA. 2007;297(13):1478–1488. Link
  13. Marmolejo VS, Arnold JF, Ponticello M, Andersen CA. Charcot foot: clinical clues, diagnostic strategies, and treatment principles. Am Fam Physician. 2018;97(9):594–599. Link
  14. Matheson EM, Bragg SW, Blackwelder RS. Diabetes-related foot infections: diagnosis and treatment. Am Fam Physician. 2021;104(4):386–394. Link
  15. Schaper NC, Van Netten JJ, Apelqvist J, et al. IWGDF 2023 practical guidelines on the prevention and management of diabetes-related foot disease. Diabetes Metab Res Rev. 2024;40(3):e3657. Link
  16. Grimer RJ, Briggs TWR. Earlier diagnosis of bone and soft-tissue tumours. J Bone Joint Surg Br. 2010;92-B(11):1489–1492. Link
  17. Osteosarcoma — Foot and Ankle. BoneTumor.org. Link

Red flags for other regions: Neck · Shoulder · Elbow · Wrist and hand · Thoracic spine and chest wall · Low back and pelvis · Hip and groin · Knee

One study, one test, once a month

Rule It In is a free evidence letter for musculoskeletal clinicians: one recent study explained, one examination test with its real numbers. From Trokos, publisher of Rule It In, Rule It Out.

Free when you confirm your email: a one-page PDF of the strongest special tests to rule in and rule out, with tests that carry a caution flagged separately.