Diabetic Foot Conditions: Diagnosis and Management

Primary Diagnostic Considerations

The American Diabetes Association recommends suspecting active Charcot neuro-osteoarthropathy (CNO) in patients with diabetes and neuropathy presenting with a unilateral red, warm, swollen foot with intact skin and no history of ulceration 1, 2
Clinical signs of CNO include hyperaemia, increased foot skin temperature, and edema, with pain that may be absent or relatively mild due to sensory neuropathy 1, 2
A temperature difference ≥2°C between the affected and unaffected foot at the same anatomical location strongly suggests active CNO 1, 2
Left untreated, CNO presents a high risk of bone fractures, dislocations, deformity, ulceration, infection, and amputation with major lifelong consequences 1, 2
Infection requires at least two of the following: local swelling/induration, erythema >0.5 cm around any wound, local tenderness/pain, local warmth, or purulent discharge 3
Other inflammatory conditions must be excluded: trauma, gout, acute Charcot neuro-osteoarthropathy, fracture, thrombosis, and venous stasis 3
The presence of ulceration and infection does not preclude underlying active Charcot—both can coexist 4

Gout should be considered in patients with acute onset, severe pain, and history of hyperuricemia or prior attacks 3
Deep venous thrombosis must be excluded with appropriate clinical assessment and D-dimer/ultrasound if indicated 1, 3
Soft tissue infection without diabetes requires at least two inflammatory signs (redness, warmth, swelling, tenderness, purulent discharge) 3

The American College of Foot and Ankle Surgeons recommends initiating knee-high immobilization/offloading promptly in patients with diabetes and neuropathy while further diagnostic studies are performed to confirm or rule out active CNO 1, 2
This is a strong recommendation even before imaging confirmation due to the catastrophic consequences of delayed treatment 1, 2
Palpate for point tenderness: Achilles insertion, lateral malleolus, posterior superior calcaneus, lateral calcaneal wall, and calcaneofibular ligament course 5
Perform calcaneal compression test (medial-to-lateral squeeze) to evaluate for stress fracture 5, 6
Measure skin temperature using infrared thermometry at multiple sites on both feet, comparing the highest temperature on affected foot to the same anatomic point contralaterally 1, 2

Obtain plain X-rays of the foot in all cases to evaluate for fractures, dislocations, or bone destruction 3, 7, 8
Plain radiographs may be normal in early CNO (stage 0) and early stress fractures 4, 5
MRI is the preferred advanced imaging modality for diagnosing active CNO, showing bone marrow edema without fractures in early stages 4, 7, 8
Technetium bone scanning for suspected stress fracture with negative initial radiographs 5, 6

Never delay immobilization in diabetic patients with neuropathy and a hot swollen foot while waiting for imaging—the consequences of untreated CNO are devastating 1, 2
Do not assume the absence of pain rules out serious pathology in diabetic patients with neuropathy, as pain may be minimal or absent 1, 2
Do not diagnose based on imaging alone—combine symptoms, clinical signs, and imaging findings 4

Immediate subspecialist referral for suspected active CNO to prevent progression to deformity and ulceration 1, 2, 4
Suspected osteomyelitis requiring bone biopsy for definitive diagnosis or antibiotic sensitivity testing 3
No improvement after 6-8 weeks of appropriate conservative treatment for other conditions 5
Consideration of surgical intervention for recalcitrant cases 5