Gabriella Bargon, Sue Deacon, Sharon Tsang, Lena Wallin
Intrinsic lateral rotators
Quadratus femoris was identified as a flat quadrilateral muscle, which arises from the ischial tuberosity and inserts onto the quadrate tubercle of the femur. Immediately superior to it was the tiny muscle belly of the obturator externus. Although the origin of this muscle was not identified, due to the constraints of the dissection procedure, it was evident that the size of the muscle belly expanded as it approached the obturator foramen. The insertions of the obturator externus and the quadratus femoris were considerably more distal than the other posterior hip muscles, which explains the fact that they maintain their external rotation moment throughout all ranges of hip flexion (Delp et al 1999).
The short external rotators are all tested simultaneously. Variations exist in the testing procedure for this muscle group. It has been reported in both a position of hip flexion (90 degree) (Kendall et al 1993) and in approximately 30 degree of flexion (Sahrmann 2002). The former position does not appear appropriate as most of the short external rotators develop internal rotation moments in this position (Delp et al 1999, Dostal et al 1986). Although the 'clam' position, suggested by Sahrmann (2002), does address the abduction component of these muscles, neither tests consider their other functions in more extreme positions of hip flexion. These tests also fail to address the eccentric action of quadratus femoris in controlling internal rotation. This lack of control has been linked to sports related injuries (Klinkert et al 1997, Peltola et al 1999, Willick et al 2002).
