Download Muscles of the Thigh - Our Movement Powerhouse

Muscles of the Thigh - Our Movement Powerhouse
November 2015 --- Jim Smyth, RMT
This brief article outlines the major muscles of the thigh, some
of their history, how they interact and the role they play in
getting us from one place to another.
The thigh is organized into four quadrants – lateral (outside),
anterior (front), medial (inside) and posterior (back).
The lateral quadrant is formed by a band of connective tissue
(fascia) called the Iliotibial Tract; it connects to the pelvis, hip
and just below the knee. This thick fascia does not contract
like muscle, but is crucial for stabilizing the knee when we are
standing, walking and running. Control of this band during
movement is by an anterior thigh muscle (Tensor Fascia Lata
or TFL) and posteriorly by the large buttock muscle (Gluteus
Maximus). These two muscles work together and assist other
muscles in moving the thigh the forward and backward (flexion
and extension).
The main group in the front is the quadriceps (Latin - four
heads). They are primarily responsible for extending (straightening) the knee. All surround the knee cap (patella) and insert
on the tibia (lower leg) just below the knee. These four muscles
are a major contributor of the power we need to walk and run. Two other large hip flexors (Iliacus and Psoas)
control our sitting and squatting movements, with some assistance from one of the quadriceps (Rectus Femoris) and
the TFL. The Sartorius (tailor muscle) allows us to cross our ankle at the knee, so that we can sew or crochet.
The hamstrings make up the posterior thigh. Their job is to extend or move back the thigh and flex (bend) the knee.
These three muscles are typically about one-third as strong as the quadriceps. Their name comes from hanging up
hams (pig thighs) from the tendons at the back of the knee. In ancient times to hamstring an enemy you would cut
the tendons at the back of the knee, so they could not run.
The action of the medial group is to adduct the thigh (e.g. the action of holding oneself on a horse). The largest of
this group (Adductor Magnus) also assists the hamstrings with extending the leg.
When one of the groups is the prime mover each one of the other groups will act as a synergist, to counter-balance,
stabilize and assist with controlled movement. So if you are moving to a standing position from a chair, the prime
movers are the quadriceps; the adductors, the hamstrings and the hip flexors will act as synergists so that the
movement is coordinated and smooth. In fact, a myriad other of muscles in the body will also coordinate and
co-operate as both prime movers and synergists, to assist in just this one movement of moving to a standing
position.
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