Risk Categories in Diabetic Foot Syndrome: Classification, Monitoring Intervals and Prescription

What lies behind it

Diabetic foot syndrome is one of the most complex long-term complications of chronically elevated blood sugar levels. A persistent state of hyperglycaemia damages both peripheral nerve pathways and arterial blood vessels over the years. The medical community primarily distinguishes between diabetic neuropathy, which impairs nerve function, and peripheral arterial disease, abbreviated as PAD, which leads to circulatory disorders. Affected individuals frequently present with a mixed form referred to as neuroischaemic foot syndrome.

In order to objectively assess the individual risk of skin defects, ulcers, or tissue necrosis, the German Diabetes Society and the Federal Joint Committee have established a clear classification system. These risk classes form the basis for the frequency of medical follow-up examinations and the eligibility for reimbursement of podiatric treatment under the Remedies Directive (Heilmittel-Richtlinie).

1. Risk Class 0: Diabetes mellitus is present, but without verifiable peripheral neuropathy and without peripheral arterial disease. The risk of acute foot complications is low at this stage, but requires an annual check-up.
2. Risk Class 1: Proven peripheral neuropathy or peripheral arterial disease is present, but there are no foot deformities or signs of structural skin damage yet.
3. Risk Class 2: Peripheral neuropathy or peripheral arterial disease is present in combination with foot deformities such as hammer toes, claw toes, or hallux valgus, or signs of pressure overload such as marked callus formation.
4. Risk Class 3: Healed ulcers in the medical history, previous amputation in the foot region, diagnosed inactive Charcot foot, or end-stage renal disease requiring dialysis.

Diagnostics to determine these risk classes are carried out using standardised examination procedures. The testing of skin sensitivity is performed using the Semmes-Weinstein monofilament, a calibrated plastic filament that buckles under a defined pressure of ten grams. Vibration perception is assessed at the medial malleolus and the first metatarsophalangeal joint using a Rydel-Seiffer tuning fork. To evaluate arterial circulation, palpation of the foot pulses at the dorsalis pedis artery and posterior tibial artery, as well as measurement of the ankle-brachial index via Doppler sonography, are utilised.

Typical signs

The perception of warning signals on the feet is often severely impaired by diabetic neuropathy. The loss of pain and temperature sensitivity causes pathological processes to remain unnoticed for a long time. At the beginning, affected individuals often report a feeling of numbness in the toes, which can expand upwards in a stocking-like distribution. Paraesthetic sensations such as tingling, electrifying stabs, or the burning feet phenomenon also tend to occur primarily during periods of rest at night.

In addition to sensory deficits, autonomic neuropathy impairs the function of the sweat glands. The skin on the feet loses its natural moisture and becomes dry, brittle, and cracked. Deep skin fissures, known as rhagades, develop on the heels and can serve as entry points for bacterial pathogens. Furthermore, the loss of motor nerves leads to atrophy of the small foot muscles, resulting in toe deformities and a shift in pressure load onto the metatarsal heads.

If peripheral arterial disease is predominantly present, signs of inadequate tissue perfusion dominate. The skin appears cool, pale, or cyanotic. During exertion, such as walking longer distances, muscular pain develops in the calf or foot arch, which subsides after short rest periods. In advanced stages, pain at rest and during the night occurs, particularly when the legs are elevated. The absence of foot pulses during physical examination is a clear finding of vascular involvement.

Differential diagnosis distinguishes diabetic foot syndrome from purely venous outflow disorders, lymphatic oedema, or orthopaedic overuse syndromes. While venous congestion is characterised by brownish skin pigmentation and fluid accumulation in the tissue, it usually lacks the characteristic neurological deficits associated with diabetes-induced nerve damage.

Everyday causes

In daily life, numerous mechanical, thermal, and chemical influences act on the feet, which in healthy individuals are cushioned by intact protective reflexes. In diabetic patients with neuropathy, this natural warning system is completely absent. Footwear that is too tight, hard or worn-out heel counters, and protruding internal seams generate continuous pressure on the paraesthetic tissue. As the pain stimulus is absent, the skin reacts with increased keratinisation, beneath which bleeding and ultimately ulceration can occur.

Walking barefoot also poses considerable hazards in daily life. Small foreign bodies such as pebbles, glass splinters, or needles penetrate the sole of the foot painlessly and often remain there for days. Similarly, unsuitable insoles or worn-out shoe tread lead to altered peak pressures beneath the metatarsal bones. Due to the impaired biomechanics, thick callus forms at points of maximum load, pressing like a wedge into the underlying soft fatty tissue.

Thermal injuries frequently result from careless measures to warm the feet. Due to reduced temperature sensitivity, foot baths are often prepared too hot, or hot water bottles and electric heating pads are placed directly against cold feet. The result is second- or third-degree scalds and burns that heal with extreme difficulty. Chemical causes usually lie in the unauthorised use of over-the-counter corn plasters or callus removers containing aggressive salicylic acid, which macerates healthy tissue.

Hygiene and grooming errors contribute further to the development of complications. Incorrect shortening of toenails using sharp instruments, rounding off the nail corners, or cutting into the lateral nail folds leads to minor cut injuries. Since the eyesight of many diabetic patients is also impaired by diabetic retinopathy, the risk of self-injury during home foot care increases massively.

When medical evaluation is necessary

Any newly developed skin change on a diabetic patient's foot requires prompt evaluation by a specialist physician. Waiting for spontaneous improvement is dangerous due to the accelerated spread of infection associated with impaired metabolism. As soon as an open wound, a blister, painless skin redness, or localised warming of the tissue is noticed, an immediate diabetological or vascular surgical evaluation must be arranged.

Particular urgency is required if accompanying symptoms such as purulent secretion, a foul odour from the wound, or streak-like redness indicative of lymphangitis occur. General signs of infection such as fever, chills, or inexplicably severe blood sugar spikes also point to a severe, deep-seated infection. Here, the risk of phlegmon or osteomyelitis exists, which permanently destroys tissue and bone structure.

Sudden swelling of the entire foot without preceding trauma, accompanied by distinct warming and redness, can indicate active Charcot foot. In this neuro-arthropathic condition, painless microtrauma leads to bone fractures and joint dislocations in the foot skeleton. Immediate pressure relief and immobilisation by a specialist physician are imperative to prevent a collapse of the foot arch.

Medical care ideally takes place within an interdisciplinary network. Diabetologists, vascular surgeons, podiatrists, orthopaedic footwear technicians, and specialised wound managers work closely together to seamlessly maintain the continuum of wound treatment, pressure relief, and infection control.

What podiatric treatment can achieve

The podologische Komplexbehandlung (comprehensive podiatric treatment) is a targeted medical measure for the prevention and treatment of foot complications in diabetes mellitus. In contrast to cosmetic foot care, gentle, debriding, and injury-free tissue treatment takes priority here. Prior to commencing the actual treatment, a thorough visual and physical examination is performed, carefully documenting skin condition, pulse status, and any pressure points.

Mechanical removal of hyperkeratosis, calluses, and rhagades is carried out using sterile scalpel blades and rotating diamond burrs. Modern wet spray or suction techniques consistently prevent thermal damage to tissue caused by frictional heat. Controlled thinning of excessive callus relieves pressure from the underlying soft tissue, preventing the formation of subhyperkeratotic haematomas or ulcers.

When treating toenails, correct shortening and contour filing are central. Ingrowing nails, onychomycosis, or thickening of the nail plate such as onychauxis are treated professionally. To free the lateral nail fold from hyperkeratosis, fine probing and hollow chisel instruments are utilised. If a nail deformity leads to recurrent inflammation, the podiatry practice can apply orthonyxia (nail bracing) techniques for remediation.

1. Removal of pathological skin thickenings while considering individual tissue boundaries.
2. Professional treatment of altered nail plates and care of the delicate nail unit.
3. Fabrication of custom-fitted pressure and friction protection devices made of medical silicone to relieve deformed toes.
4. Regular assessment of the foot condition and assignment to the corresponding monitoring intervals.

The duration of a comprehensive podiatric treatment session is usually between 30 and 45 minutes. The interval between individual treatments depends strictly on the medically diagnosed risk class. While intervals of eight to twelve weeks may be sufficient for Risk Class 1, Risk Classes 2 and 3 require treatment cycles every four to six weeks. Statutory health insurance covers the costs of these medical treatments if a valid prescription for remedies (Muster 13 form) from the attending physician is present. Further information on our treatment options can be found in the /en/services section as well as under /en/sectoral-practitioner.

What you can do yourself

Rigorous self-examination forms the most important pillar in the daily prevention of foot damage. Affected individuals should establish a fixed routine to systematically inspect their feet for changes every day. As the soles of the feet are difficult to view, using a shatterproof hand mirror, a telescopic mirror placed on the floor, or a digital camera is recommended.

Daily washing of the feet should be done in lukewarm water. The water temperature must be checked with a bath thermometer and must not exceed 37 degrees Celsius. The duration of the foot bath should be limited to a maximum of three to five minutes, as longer bathing macerates the skin and weakens its natural protective barrier. After washing, the feet must be dried thoroughly, paying particular attention to the spaces between the toes to prevent fungal infections.

To maintain skin elasticity, daily application of a moisturising emulsion to the foot is necessary. Preparations containing urea at a concentration of five to ten percent are recommended. The interdigital spaces between the toes must be strictly avoided during moisturising, as moisture accumulation in these areas favours the growth of dermatophytes.

Before putting on shoes, their interior should be thoroughly checked by hand. This ensures that no foreign bodies, folded insoles, or protruding seams are present inside the shoe. The footwear itself should offer sufficient room for the toes, feature soft lining, and have no pressing seams over the toe joints. Socks should be made of natural, breathable materials, have no constricting elastic bands, and avoid internal seams.

Common mistakes

In practice, recurring behaviours frequently emerge that unintentionally increase the risk of severe foot complications. The most serious error is the unauthorised use of sharp blades, razor scrapers, or callus rasps for home tissue removal. Due to the lack of pain perception, patients often cut deep into healthy skin layers, resulting in slow-healing wounds and infections.

Another common misconception concerns the treatment of corns and pressure points with over-the-counter liquids or plasters. These products contain high concentrations of acids designed to chemically dissolve keratinised tissue. In the presence of neuropathy, the acid penetrates unhindered into deeper tissue layers, causing chemical burns that can rapidly develop into deep ulcers.

Walking barefoot in the home, garden, or on the beach poses an immense risk. Even on seemingly clean carpets, small objects such as pins or small wooden splinters can lie on the floor and penetrate the sole of the foot painlessly. Similarly, walking on hot tiles or warm sand during summer is underestimated, which can quickly lead to extensive blister formation.

Mistakes are also frequently made when cutting toenails. Rounding the edges of the nails deep into the lateral fold promotes subsequent ingrowing of the nail plate. Nails should always be trimmed straight across, and the corners gently deburred using only a fine glass or emery board file. Finally, ignoring small blisters, pressure points, or redness often causes valuable time to pass before adequate therapy is initiated.

Study evidence and clinical context

The medical evidence regarding the effectiveness of structured risk classifications and podiatric prevention is comprehensively documented in international guidelines from the International Working Group on the Diabetic Foot and the National Care Guideline for Type 2 Diabetes. Studies prove unequivocally that regular podiatric care combined with adequate therapeutic footwear can reduce amputation rates in high-risk patients by up to 80 percent [1].

The diagnostic accuracy of the Semmes-Weinstein monofilament combined with vibration perception testing is considered the gold standard in medical literature for the early detection of diabetic polyneuropathy [2]. Studies show that the absence of protective sensation under monofilament testing is the strongest predictor for the future occurrence of a diabetic foot ulcer.

Clinical research likewise demonstrates that mechanical pressure relief is the central prerequisite for the healing of existing tissue defects and the prevention of recurrence [3]. The combination of medical treatment and individually fitted orthopaedic aids significantly reduces peak pressure beneath the metatarsal heads. Systematic classification into Risk Classes 0 to 3 ensures that therapeutic resources are purposefully deployed where the highest potential hazard exists [4].

Treatment in Memmingen

At the FREITAG® Podologie GmbH practice at Kempterstr. 25 in 87700 Memmingen, we offer professional and medically sound care for the diabetic foot. As a state-recognised podiatrist and sektorale Heilpraktikerin für Podologie (sectoral practitioner of podiatry), Helga Maria Freitag possesses the necessary qualifications to precisely evaluate tissue changes, treat according to risk, and implement required preventive measures.

Our practice serves patients from Memmingen as well as the entire surrounding region of the Unterallgäu, Allgäu, and Upper Swabia. We work closely with local general practitioners, diabetologists, and medical specialists. Statutory health insurance patients with a documented risk class can receive comprehensive podiatric treatment at our premises based on a medical prescription for remedies (Muster 13 form).

You are welcome to arrange an appointment for an initial assessment and have your feet professionally examined. Please use our contact options at /en/contact or learn more about our facility in the /en/practice section. We provide competent and reliable support to help preserve your mobility.