Tendons are an essential tissue that join together and transmit force between muscle and bone. While much is known about muscle and skeletal growth mechanisms, remarkably little is known about the induction and regulation of tendon growth. Failure of the muscle-tendon unit (MTU) to accommodate skeletal growth can result in reduced joint mobility called contractures, a common impairment in a variety of juvenile orthopedic conditions. Joint contractures are often treated by surgical lengthening of the tendon; however, this approach frequently results in tendon scarring and a recurrence of the contracture. This recurrence may be a symptom of impaired tendon development in growing children following surgery. Innovative mechanisms of tendon elongation are necessary to improve outcome. This dissertation project aimed to find key signals and processes that direct tendon elongation during development.