Dr Otieno received his MBChB degree and his MMed degree in Internal Medicine the University of Nairobi. He later pursued a clinical fellowship in Rheumatology from the University of Liverpool.

Previously, Dr Otieno was a consultant Physician and Rheumatologist at the Nairobi Arthritis Clinic, and various private hospitals in Nairobi (Nairobi Hospital, Mater Hospital, MP Shah Hospital, Coptic Hospital and Nairobi West Hospital).

He is a member of several professional organizations:  Secretary Arthreuma Society of Kenya, Secretary Uwezo Rheumatology Society, and Member British Society for Rheumatology, Member American College of Rheumatologists, Member East and Central Africa College of Physicians, Member Kenya Association of Physicians. He is also a fellow of The Royal College of Physicians (Edinburg)

His research interests include the epidemiology of rheumatic diseases in developing countries and clinical correlates of patients with common rheumatic conditions.