The muscle indicated is the gracilis.
The gracilis is one of six muscles in the medial compartment of the thigh. The thigh consists of three muscular compartments:
The medial compartments consists of the following muscles:
3) Adductor longus
4) Adductor brevis
5) Adductor magnus
6) Obturator externus
The gracilis is the most superficial muscle in the medial compartment. It is a thin muscle which descends vertically down the medial aspect of the thigh.
Origin: inferior pubic ramus, ramus of ischium
Insertion: proximal shaft of tibia medially (pes anserinus)
Action: Adduction of thigh at hip join, flexion of knee
Innervation: Obturator nerve
The tendon of the gracilis inserts just above the point at which the semitendinosus muscle insertions and just behind the point where the sartorius inserts. The tendons of these three muscles (semitendinosus, gracilis and sartorius) are jointly referred to as the pes anserinus.