Polyarthritis is an infectious disease of nursing lambs, recently weaned lambs, and feedlot lambs. Symptoms are stiffness, reluctance to move, depression, loss of body weight, and conjunctivitis. Clinically the disease is primarily characterized by stiffness and by conjunctivitis. Usually the affected lamb's appetite remains good, but it may be too lame to graze or search for food. Affected joints are typically not enlarged, and stiffness and lameness are less apparent after lambs are forced to exercise. Kneeling and abnormal position of the limbs are sometimes observed. Lambs can be treated with several different broad-spectrum antibiotics or tetracycline drugs. Affected lambs should be confined in a dry, well-bedded area with readily available feed and water. Additionally, supplying antibiotics in the feed can be beneficial in feedlot conditions. Early isolation of lame lambs during an outbreak and addition of specific antibiotics to the feed may help control the disease.