This paper examines the case of differential diagnosis of diabetic neuroosteoarthropathy (DNOA) and purulent arthritis (PA) in young patients with unsatisfactory control of type 1 diabetes mellitus (T1DM) and a short (8 years) duration of the underlying disease. Errors in the diagnosis of foot and ankle lesions made at the first stage of care create a clinical situation associated with a minimal risk of limb loss. At the second stage, during hospitalization in a specialized institution, a range of diagnostic and therapeutic measures was selected, which allowed for adequate diagnosis and differential diagnosis of the lesion, as well as its complex treatment, which made it possible to save the foot and ankle joint. This harmful event is due to the need for comprehensive multidisciplinary care in the selection of diagnostic testing and subsequent treatment of short-term patients with poorly controlled type 1 diabetes mellitus.