How to Inject the Synovial Cavities of the Digit

Arthrocentesis of the equine interphalangeal joints and synoviocentesis of the digital synovial sheath is commonly performed for diagnostic analgesia as part of a lameness examination and to medicate these structures. The techniques for arthrocentesis are the same for the forelimb and the hind limb. Restraint is achieved by applying a lip twitch to the horse. Tranquilization or sedation is rarely used for restraint when centesis of these structures is part of a lameness examination, but in some cases tranquilizing or sedating the horse may be necessary to increase the safety of the procedure. Administration of a low dose of xylazine, detomidine, or acepromazine is unlikely to interfere with gait evaluation and in some cases may even accentuate lameness. If centesis is performed with the foot bearing weight, the contralateral limb can be held by an assistant. Some horses, however, may buckle at the carpus when the needle is inserted, causing injury if the carpus strikes the ground.