Final answer:
Athletic pubalgia, or sports hernia, primarily involves tenderness in the adductor longus muscle, which is a main inner thigh muscle. Other nearby muscles including the gracilis, adductor magnus, and sometimes the sartorius may also be affected in this region near the pelvic girdle.
Step-by-step explanation:
In the condition known as athletic pubalgia, more commonly referred to as sports hernia, the muscle that is typically involved and becomes tender is the adductor longus. This muscle is one of the main muscles of the inner thigh that helps in adduction, the movement of bringing the leg back towards the midline of the body. The pelvic girdle area, particularly where the adductor muscles attach to the pubic bone, is the region that experiences the strain or tear that characterizes athletic pubalgia. Alongside the adductor longus, other muscles such as the gracilis, adductor magnus, and sometimes the sartorius may also be affected. The injury could extend to involve the quadriceps tendon or the patellar ligament due to their proximity and interconnected muscle actions.