It is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading.
It ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the forearm.
This procedure is indicated in a child aged 22.5 years with dynamic supination of the foot.
This could involve rapidly switching from pronation to supination of the forearm.
Straightening the arm does not alleviate the pressure, since the shoulder joint does not allow further supination of the hand.
However, it is not attached to the ulna medially, as the distance between these two bones varies with supination and pronation of the forearm.
This movement is known as a pronation/supination test of the upper extremity.
Along with the transverse tarsal joint (i.e. talonavicular and calcaneocuboid joint), the subtalar joint transforms tibial rotation into forefoot supination and pronation.
