Module 3: Common Foot Conditions & Diseases
Module 3 of 10 · Lesson 5 of 5
Module 3 · Lesson 5
Diabetic Foot & Pressure Injuries
Learning Objectives
By the end of this lesson, the learner will be able to:
- Describe how diabetic peripheral neuropathy and peripheral artery disease combine to produce diabetic foot complications.
- Stage a pressure injury using the current National Pressure Injury Advisory Panel (NPIAP) classification — including Unstageable and Deep Tissue Pressure Injury.
- Classify a diabetic foot ulcer using the Wagner Grading System.
- Stratify a patient's diabetic foot risk using the IWGDF risk categories and assign appropriate visit intervals.
- Apply structured nursing assessment, prevention, and timely escalation to reduce ulceration, hospitalization, and amputation.
This is the highest-stakes content in foot care nursing. Diabetic foot complications are the leading cause of non-traumatic lower extremity amputations in the United States — and the great majority are preceded by an ulcer that could have been detected earlier or prevented entirely. Nurses sit at the front of that prevention pathway. This lesson covers the mechanisms, the staging frameworks you'll be expected to know, and the actions that change outcomes.
Why the Diabetic Foot Is Different
Two parallel processes drive most diabetic foot complications. They almost always travel together.
Chronic hyperglycemia damages peripheral nerves, classically producing a stocking-distribution sensory loss. Patients lose the protective sensation that warns them of injury.
- Loss of light touch and pain perception
- Tingling, burning, or numbness
- Foot deformity from intrinsic muscle wasting (advanced)
- Autonomic involvement causes dry, cracked skin
A patient walks all day with a tack in their shoe and doesn't notice. By the time they remove the shoe, the wound is already established.
Atherosclerosis of the lower-extremity arteries reduces perfusion to the foot. Tissue that already had a low margin for injury now has no oxygen reserve to repair itself.
- Diminished or absent pedal pulses
- Cool feet, pallor on elevation, dependent rubor
- Slow-healing or non-healing wounds
- Intermittent claudication; rest pain in advanced disease
A small cut that would heal in 5 days on a healthy foot persists for weeks — long enough to colonize, infect, and break down further.
The diabetic foot ulcer pathway
Three forces converge to produce an ulcer
Foundational principle
The diabetic foot ulcer is rarely caused by any single factor. It is the convergence of unrecognized injury (because of neuropathy), inability to heal (because of ischemia), and unrelieved pressure (because of mechanics or footwear). Effective nursing care addresses all three.
Pressure Injury Staging (NPIAP)
The National Pressure Injury Advisory Panel (NPIAP) updated the framework in 2016 — including a terminology change you should know.
Terminology update
NPIAP replaced "pressure ulcer" with "pressure injury" in 2016 to reflect that the earliest stage involves intact skin (no ulcer present yet). Older charts and some texts still use "pressure ulcer." Both refer to the same condition. Modern documentation should use "pressure injury."
Non-blanchable erythema
Intact skin with a localized area of non-blanchable redness. Skin may feel warmer or cooler, firmer, or painful compared to surrounding tissue.
Action
Offload immediately. Reposition every 2 hours. Inspect for resolution.
Partial-thickness skin loss
Loss of epidermis and partial dermis exposing pink/red wound bed. May present as an intact or ruptured serum-filled blister.
Action
Cleanse with saline; protective dressing; offload; assess for infection.
Full-thickness skin loss
Full-thickness loss exposing subcutaneous fat. Slough or eschar may be present. Tunneling and undermining may occur. Bone, tendon, and muscle are not exposed.
Action
Refer to wound care; consider debridement; treat infection per provider.
Full-thickness loss with exposed structures
Full-thickness loss with exposed bone, tendon, muscle, or supporting structures. Slough, eschar, undermining, and tunneling are common.
Action
Urgent wound care referral; advanced therapies; rule out osteomyelitis.
Obscured by slough or eschar
Full-thickness loss in which the depth cannot be determined because the wound bed is covered with slough or eschar. Until the wound base is visible, true staging is impossible.
Action
Refer for debridement to expose wound base; do not remove stable, dry eschar on heels with poor perfusion.
Persistent purple or maroon discoloration
Intact or non-intact skin with localized area of persistent non-blanchable deep red, maroon, or purple discoloration, or a blood-filled blister. Indicates damage to underlying soft tissue.
Action
Treat as serious — may rapidly evolve to full-thickness loss even with optimal care.
The heel exception
Stable, dry, intact eschar on the heel of a patient with poor perfusion should generally not be debrided. The eschar acts as a biological cover. Debriding it can convert a covered, dry wound into an open, infected one with no healing capacity. Document, offload, and consult wound care or vascular before any intervention.
Wagner Classification: For Diabetic Foot Ulcers Specifically
The NPIAP framework above stages pressure-related skin injury. Diabetic foot ulcers — even when pressure is the proximate cause — are typically classified using the Wagner system, which captures depth and the presence of infection or gangrene.
Wagner Diabetic Foot Ulcer Classification
0
Pre-ulcerative or healed lesion
Intact skin with foot at risk: callus, deformity, prior ulceration. The window for prevention.
1
Superficial ulcer
Partial- or full-thickness ulcer not extending to subcutaneous tissue.
2
Deeper ulcer
Penetrates to ligament, tendon, joint capsule, or fascia. No abscess or osteomyelitis.
3
Deep ulcer with abscess or osteomyelitis
Tissue infection or bone involvement. Requires imaging and aggressive management.
4
Localized gangrene
Gangrene limited to a portion of the foot — typically a toe or forefoot.
5
Extensive gangrene
Gangrene of the entire foot. Surgical management — typically amputation — is required.
Risk Stratification: How Often to See the Patient
The IWGDF risk categories are the standard for stratifying diabetic foot risk and assigning visit intervals. Knowing which category a patient is in is one of the highest-yield CFCN exam topics.
0
Very low risk
No loss of protective sensation (LOPS) and no peripheral artery disease (PAD).
Frequency
Annually
1
Low risk
LOPS or PAD present, but not both. No history of ulcer or amputation.
Frequency
Every 6–12 months
2
Moderate risk
LOPS plus PAD; or LOPS plus foot deformity; or PAD plus foot deformity.
Frequency
Every 3–6 months
3
High risk
LOPS or PAD AND a history of foot ulcer, lower-extremity amputation, or end-stage renal disease.
Frequency
Every 1–3 months
Why prior ulceration matters so much
A patient who has had a diabetic foot ulcer is at substantially elevated risk of recurrence — roughly 40% within one year and 65% within five years per IWGDF data. Prior ulceration immediately moves a patient into the highest risk category regardless of current foot status.
Structured Diabetic Foot Assessment
The same Look–Feel–Pulse framework used for other foot exams, intensified for the diabetic foot.
Step 1 · Look
Visual inspection
- Inspect every surface — top, bottom, between toes, heels, and inside footwear
- Look for ulcers, blisters, calluses (a callus on a neuropathic foot is a pre-ulcer)
- Note any color changes: pallor, dependent rubor, blue or purple discoloration, blackening
- Identify deformities: hammertoes, Charcot deformity, prominent metatarsal heads
Step 2 · Feel
Sensory testing
- 10g monofilament at the 9 standard plantar sites (avoid callused areas)
- 128 Hz tuning fork on the dorsum of the great toe for vibration sense
- Loss of sensation at any site = loss of protective sensation (LOPS)
- Compare bilaterally; new asymmetric findings warrant escalation
Step 3 · Pulse
Vascular assessment
- Palpate dorsalis pedis and posterior tibial pulses; document grade bilaterally
- Capillary refill at the great toenail (≤3 seconds)
- Skin temperature; an abrupt change is a red flag
- Diminished pulses or symptoms of claudication warrant Ankle-Brachial Index (ABI)
Red flags for urgent escalation
Any new ulcer in a patient with diabetes, any wound with surrounding cellulitis or systemic symptoms (fever, chills, malaise), abrupt change in foot color or temperature, exposed bone or tendon, or signs of gangrene — escalate immediately. Diabetic foot infections can progress from local to limb-threatening within 24–48 hours.
Prevention & Patient Education
The single largest impact in diabetic foot care comes from prevention. Most ulcers are foreshadowed by callus, deformity, or footwear pressure points the patient cannot feel.
Patient Teaching
Six daily habits that prevent ulceration
Daily foot inspection
Use a mirror or caregiver if needed
Never barefoot
Even at home, even briefly
Check shoes before wearing
Look and feel inside for objects
Moisturize daily
Heels and dorsum, not between toes
Professional nail care
Especially with neuropathy
Call promptly
Any new wound, redness, or color change
Patient Teaching Moment
A 67-year-old man with type 2 diabetes (12 years) and a prior healed great toe ulcer presents for routine foot care. He has reduced monofilament sensation at three plantar sites, palpable but diminished pedal pulses, and a callus over the first metatarsal head. By IWGDF criteria he is risk category 3 (highest). Beyond the immediate care — documenting findings, reducing the callus, examining for sub-callus breakdown — the nurse schedules every-1–3-month follow-up, reinforces never-barefoot, and confirms the patient has appropriate diabetic footwear. Prior ulceration plus current findings make every visit a prevention visit.
Ready to check your understanding? Take the quick knowledge check for this lesson.
✓ End of Module 3
You've completed Common Foot Conditions & Diseases
Next up: Module 4 — Foot Care Tools, Sterilization & Infection Control.
Educational Disclaimer
The information on this website and any communication with RNscrub Foot Care is provided for educational and informational purposes only. It is not a substitute for medical advice, diagnosis, or treatment. Patients are always encouraged to consult with their primary care provider or appropriate specialist for individual clinical decisions.
References
- National Pressure Injury Advisory Panel (NPIAP). Pressure Injury Stages. 2016 (revised).
- European Pressure Ulcer Advisory Panel, NPIAP, and Pan Pacific Pressure Injury Alliance. Prevention and Treatment of Pressure Ulcers/Injuries: Clinical Practice Guideline. 3rd ed. 2019.
- Wagner FW Jr. The dysvascular foot: a system for diagnosis and treatment. Foot & Ankle. 1981;2(2):64–122.
- International Working Group on the Diabetic Foot (IWGDF). IWGDF Guidelines on the Prevention and Management of Diabetes-Related Foot Disease. 2023.
- Bus SA, Lavery LA, Monteiro-Soares M, et al. Guidelines on the prevention of foot ulcers in persons with diabetes (IWGDF 2023 update). Diabetes/Metabolism Research and Reviews. 2024;40(3):e3651.
- Armstrong DG, Boulton AJM, Bus SA. Diabetic Foot Ulcers and Their Recurrence. New England Journal of Medicine. 2017;376(24):2367–2375.
- American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes — 2024 (Section 12). Diabetes Care. 2024;47(Suppl 1).
- Lipsky BA, Senneville É, Abbas ZG, et al. Guidelines on the diagnosis and treatment of foot infection in persons with diabetes (IWGDF 2023 update). Diabetes/Metabolism Research and Reviews. 2024;40(3):e3657.