Arthritis after mumps and measles vaccination.

Measles, mumps, and rubella vaccine carries a risk of joint symptoms particularly in children under 5 years. A boy who presented with an inflamed knee after measles and mumps vaccination is reported; synovial fluid aspirated from the joint contained 4.3 x 10(9)/l leucocytes. It is thought that the mumps component is the aetiological cause of acute monoarthritis.