Collectively, the muscles of the thigh are designed to move the leg, thigh, and hip of the body in a variety of directions. The three main groups of the thigh muscles include the adductors, the extensors, and the flexors, each with distinct functions within the system. Most people are familiar with the terms quads or hamstrings, and those sections of the thigh have specialized, individual muscles responsible for producing different actions and working together to complete essential movements. The thigh muscle group contains some of the largest muscles in the body and which are located on the anterior, or front of the leg, the posterior, or back of the thigh, and medially, or inside of the leg.
The adductor muscles of the thigh are responsible for bringing the thigh and hip closer to the medial aspect, the invisible middle line of the body. These muscles are used for a huge variety of movements and include the adductor brevis, longus, gracilis, and the adductor magnus, and are known as the quadriceps of the thigh. They are located on the interior of the thigh and, among other functions, separate the extensor group from the flexor group found on the posterior thigh. Most of these muscles originate on one of the bony structures of the pubis and end near or on the interior aspect of the knee joint.
Extensor muscles of the thigh work together to extend the thigh and hip, especially during activities such as walking and kicking. They are located on the anterior, or front of the thigh, and are the most visible of the thigh muscles. This group consists of the sartorius, the rectus femoris, vastus lateralis, and the vastus medialis. The majority of these muscles originate on the ilium of the pubis and end in the region near the patella of the knee. Though uncommon, a strain in one of these muscles is likely to be severe and requires time to heal.
The final group of the muscles of the thigh is the flexor muscles, or as they are more commonly known, the hamstrings. These muscles are located on the posterior aspect, or back of the thigh, and are responsible for flexing the thigh and hip for activities such as walking up or down stairs and standing up from a seated position. The flexor muscles are the semitendinosus, the semimembranosus, and the biceps crucis. Injury to the hamstring group is relatively common, especially in athletes. Runners and other track participants often experience strains in this area.