Haematogenous septic arthritis, physitis and osteomyelitis (SAPO) is a potentially debilitating or even life-threatening disease entity encountered in foals of all ages between birth and approximately 7 months old. Correct, and complete, diagnosis and successful treatment require collaboration between specialties including medicine, anaesthesia, diagnostic imaging, surgery and rehabilitation services. However, in order to succeed, it is important that all specialties have an overall knowledge of all aspects of the disease complex. Therefore, the aim of this review is to give an overview of aetiology, presenting complaints, clinical findings, diagnostic imaging, treatment, rehabilitation and prognosis. Part one deals with all aspects of aetiology and how to make a diagnosis. Part two deals with all aspects of treatment, rehabilitation and prognosis.