The “inner thigh” is a common phrase used to describe a specific region of the upper leg. While this term is widely understood in everyday language, anatomically, this area is defined by a group of muscles known as the adductor muscle group. These muscles play a significant role in various movements and contribute to the stability of the hip and leg.
The Adductor Muscle Group
The inner thigh is composed of five muscles, known as the adductor muscle group. These muscles generally originate from the pelvis and insert onto the femur, or thigh bone, with one exception extending to the tibia. The adductor longus is a long, triangular muscle located superficially in the inner thigh, originating from the pubis and inserting into the middle third of the femur’s linea aspera. Beneath it lies the adductor brevis, a shorter, triangular muscle that also originates from the pubis and inserts higher on the femur’s linea aspera.
The largest and most powerful of this group is the adductor magnus, a fan-shaped muscle with two distinct parts: an adductor portion and a hamstring portion, originating from the pubis and ischium and inserting along a broad area of the femur. The gracilis is a long, slender muscle that extends from the pubis down to the medial side of the tibia, making it unique as it crosses both the hip and knee joints. Finally, the pectineus is a flat, quadrangular muscle situated at the top and front of the inner thigh, originating from the pubis and inserting onto the femur, and is considered the most anterior adductor of the hip.
Primary Functions of the Inner Thigh Muscles
The main function of the adductor muscle group is adduction of the thigh, which involves moving the leg towards the midline of the body. This action is essential for activities such as squeezing the legs together or maintaining balance during walking and standing. Beyond adduction, these muscles contribute to several other hip movements.
The pectineus and adductor longus muscles also assist in hip flexion, which is the action of lifting the thigh towards the torso. The posterior part of the adductor magnus, often referred to as its hamstring portion, contributes to hip extension, moving the thigh backward. Some adductor muscles, including the adductor longus, adductor brevis, adductor magnus, and pectineus, play a role in the medial (internal) rotation of the thigh, which involves turning the leg inward. The gracilis also assists with medial rotation of the knee and hip.