Osteomyelitis — infection of the bone — is one of the most consequential complications of the diabetic foot. When a foot ulcer fails to heal, the underlying bone is frequently involved, and diabetic foot osteomyelitis (DFO) is present in an estimated 20% of moderate and up to 60% of severe diabetic foot infections. Because bone infection is closely linked to the risk of lower-extremity amputation, accurate diagnosis and appropriate treatment are central to limb preservation. This article reviews how clinicians identify and manage DFO, drawing on recent international guidelines and clinical research.
Why Osteomyelitis Is Difficult to Diagnose
Bone infection in the diabetic foot rarely announces itself with the classic signs of fever and systemic illness. Peripheral neuropathy blunts pain, and impaired circulation can mute the inflammatory response, so infection may advance with few outward symptoms. The diagnostic challenge is distinguishing infected bone from the soft-tissue infection that often surrounds it, and from non-infectious conditions such as Charcot neuro-osteoarthropathy, which can mimic infection on imaging.
Several clinical clues raise suspicion. A foot ulcer that is large (greater than roughly 2 cm²), deep (more than 3 mm), or located over a bony prominence and that fails to heal despite good wound care and offloading should prompt evaluation for underlying bone infection. A grossly visible bone, or a so-called “sausage toe” with diffuse swelling, further increases the likelihood of DFO.
From Bedside Tests to Advanced Imaging
The probe-to-bone test remains a valuable bedside tool. Using a sterile blunt metal probe, the clinician assesses whether bone can be palpated at the base of the wound. A systematic review and meta-analysis found a pooled sensitivity of 0.87 and specificity of 0.83, concluding that the test can reliably rule in osteomyelitis in high-risk patients and help rule it out in low-risk ones (Lam et al., 2016).
Plain radiographs are recommended as the initial imaging study. They are inexpensive and widely available but lack sensitivity early in the disease course, since bone changes such as cortical erosion and periosteal reaction may take two weeks or more to appear. For this reason, recent work supports combining tests: a 2023 meta-analysis reported that pairing the probe-to-bone test with plain X-ray raised pooled sensitivity to 0.94, approaching the accuracy of more advanced modalities (Calvo-Wright et al., 2023).
When the diagnosis or the extent of infection remains uncertain, magnetic resonance imaging (MRI) is generally the advanced imaging study of choice, offering excellent sensitivity and anatomical detail for surgical planning. European evidence-based guidance notes that when MRI is contraindicated or equivocal, white blood cell scintigraphy or [18F]FDG PET/CT can be used, and that white blood cell imaging may be particularly helpful in distinguishing infection from Charcot arthropathy (Lauri et al., 2024). Importantly, the most reliable confirmation comes from a bone sample sent for both microbiological culture and histopathology, which also identifies the responsible organisms and guides antibiotic selection.
Principles of Treatment
Management of DFO has evolved considerably. Historically, treatment relied on prolonged antibiotics or extensive bone resection; current guidelines favor an individualized approach. The 2023 IWGDF/IDSA guidelines on diabetes-related foot infections emphasize obtaining a bone specimen for culture where feasible, selecting antibiotics targeted to the cultured pathogens, and reserving urgent surgery for situations such as spreading soft-tissue infection, necrosis, or extensive bone destruction (Senneville et al., 2023).
A key shift has been the recognition that selected cases of DFO can be treated successfully with antibiotics alone, without surgical removal of bone, particularly in the forefoot and when blood supply is adequate. Where surgery is required, conservative bone resection that preserves as much functional foot as possible is preferred over major amputation whenever the limb can be salvaged.
How Long Should Antibiotics Continue?
Duration of therapy has been a longstanding question. Traditional courses extended six weeks or longer. A randomized noninferiority pilot trial compared three versus six weeks of systemic antibiotics after surgical debridement and found similar rates of clinical remission (84% versus 73%) and adverse events between the two arms, supporting shorter courses in appropriately selected patients (Gariani et al., 2021). Guidelines now recommend that when infected bone is completely removed, only a short antibiotic course is needed, whereas longer therapy is reserved for residual infected bone.
Key Takeaways
Diabetic foot osteomyelitis is common, frequently silent, and strongly associated with amputation risk. Diagnosis is most accurate when clinical assessment, the probe-to-bone test, plain radiography, and — where needed — MRI or nuclear imaging are combined, ideally confirmed by bone culture and histology. Treatment is increasingly individualized: targeted antibiotics, conservative surgery that prioritizes limb preservation, and evidence-supported shorter antibiotic courses after complete resection. Across all of these, the underlying goals remain consistent — eradicating infection, preserving functional tissue, and reducing the burden of diabetes-related foot disease.
References
Senneville É, Albalawi Z, van Asten SA, et al. IWGDF/IDSA Guidelines on the Diagnosis and Treatment of Diabetes-related Foot Infections (IWGDF/IDSA 2023). Diabetes/Metabolism Research and Reviews. 2023;40(3):e3687.
Lipsky BA, Senneville É, Abbas ZG, et al. Guidelines on the diagnosis and treatment of foot infection in persons with diabetes (IWGDF 2019 update). Diabetes/Metabolism Research and Reviews. 2020;36(Suppl 1):e3280.
Lam K, van Asten SAV, Nguyen T, La Fontaine J, Lavery LA. Diagnostic Accuracy of Probe to Bone to Detect Osteomyelitis in the Diabetic Foot: A Systematic Review. Clinical Infectious Diseases. 2016;63(7):944–948.
Calvo-Wright MDM, Álvaro-Afonso FJ, López-Moral M, et al. Is the Combination of Plain X-ray and Probe-to-Bone Test Useful for Diagnosing Diabetic Foot Osteomyelitis? A Systematic Review and Meta-Analysis. Journal of Clinical Medicine. 2023;12(16):5369.
Lauri C, Noriega-Álvarez E, Chakravartty RM, et al. Diagnostic imaging of the diabetic foot: an EANM evidence-based guidance. European Journal of Nuclear Medicine and Molecular Imaging. 2024;51(8):2229–2246.
Gariani K, Pham TT, Kressmann B, et al. Three Weeks Versus Six Weeks of Antibiotic Therapy for Diabetic Foot Osteomyelitis: A Prospective, Randomized, Noninferiority Pilot Trial. Clinical Infectious Diseases. 2021;73(7):e1539–e1545.
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