We describe six knees in five patients, referred to us after accidental irrigation with chlorhexidine 1% in aqueous solution during arthroscopy.

All six knees developed persisting pain, swelling and crepitus with loss of range of movement. Radiographs showed loss of joint space in all three compartments due to extensive chondrolysis, with many loose bodies and synovitis. Histological examination showed partial necrosis of the cartilage, with slight non-specific inflammation and fibrosis of synovial specimens.

Care is needed in checking irrigation fluids, and these should have a distinctive colour.