Pyogenic or suppurative flexor tenosynovitis is a closed space infection of the hand. If not recognised early and treated appropriately, this infection can result in significant morbidity and loss of function. This comprehensive review contains clinically relevant information on the special anatomy, pathophysiology, diagnosis and differential diagnosis, classification, microbiology, operative therapy, complications, physiotherapy, scores and results based on literature from the last 150 years and our personal experience.