Superficially placed behind the lower arm.
Insertion. - About the middle third of the radius the tendon of this muscle is joined by a strong band of fibrous tissue (superior check ligament). Its tendon then passes behind the knee, where it is enclosed in the carpal sheath, and, coursing its way downwards, ultimately divides into two short branches, which become inserted into the posterior upper border of the small pastern bone (second phalanx).
Action. - To flex the pastern and the knee.