The most common foot problem in people with diabetes is foot ulcers, which may occur with or without infection, and gangrene. These can be either localised or involve the whole foot. People with diabetes are also at risk of rarer foot problems, including Charcot arthropathy [Boulton, 1997].

Peripheral vascular disease, peripheral neuropathy, presence of callus and joint deformity are all risk factors for foot ulceration. Infection is also involved in the process, but usually occurs after initial ulceration, rather than causing it directly [Boulton, 1997].

Both atherosclerotic peripheral vascular disease and neuropathy are more common in people with diabetes than those without, placing them at higher risk of developing foot problems. For example, hyperglycaemia is directly related to altered nerve conduction and function [Clark and Lee, 1995], therefore the prevention of diabetic microvascular complications, including peripheral neuropathy, depends on strict glycaemic control.

In a recent study assessing the causal pathways leading to foot ulceration, neuropathy was the most common component cause [Reiber et al, 1999]. Both distal symmetric polyneuropathy and peripheral (sensory) neuropathy are causative factors in the development of foot problems [Armstrong and Lavery, 1998a; Pecoraro et al, 1990].

In patients with sensory neuropathy there is a lack of protective sensation with decreased awareness of injury from foreign bodies and ill-fitting footwear. Motor nerve damage that also occurs alters the posture of the foot, concentrating pressure on to vulnerable areas. The combination of foot deformities and lack of sensation exposes people with diabetes to undue sudden or repetitive stress and eventual ulcer formation, with risk of infection and possible amputation [Boulton, 1997].

Atherosclerotic peripheral vascular disease leads to tissue ischaemia, which contributes to the formation of many diabetic foot ulcers. The presence of ulceration, with inflammation and often super-added infection, increases the demand for oxygen and nutrients that cannot be met by the compromised circulation [Boulton, 1997]. Therefore, peripheral vascular disease can impair ulcer healing [Moriarty et al, 1994].

People with longstanding diabetes and dense somatosensory and autonomic neuropathy are at increased risk of developing Charcot arthropathy. Peripheral vascular disease does not play a role in this disorder.

Although the etiology of Charcot foot is poorly understood, it is thought that the increased blood flow in the bone due to sympathetic denervation causes osteopenia, which can then lead to fracture and dislocation. The disorder can also increase the risk of ulceration [Shaw and Boulton, 1995].

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