The case records, clinical, radiographic, ultrasonographic and arthrocentesis findings from 25 cattle with septic or traumatic arthritis were reviewed. The total of 30 joints involved were: articulatio cubiti (elbow joint)-1, articulatio carpi (carpal joint)-10; articulatio genus (stifle joint)-4, articulatio tarsocruralis (tarsocrural joint)-8; articulatio metacarpo-/metatarsophalangea (metacarpo-/metatarsophalangeal joint -7. Ultrasonographic investigation was performed using 7.5 MHz linear and 5 MHz sector transducers. In eight cattle, a concurrent infection of periarticular tendon sheaths or hygroma was diagnosed. The distension of the joint cavities could be imaged in all cases. Assessing echogenicity, acoustic enhancement, ultrasonographic character of the exudate (liquid or clotted) and findings revealed by aspiration, arthrotomy or at necropsy, the synovial effusion was classified as: serous, fibrinous or fibrino-purulent. Diagnostic ultrasound provided a comprehensive preoperative diagnosis in septic and traumatic arthritis by imaging the accurate localization of soft-tissue swelling and the extent and consistency of joint effusion.