The hip joint is a complex and highly functional structure, fundamental to human movement and stability. It allows for activities such as walking, running, and jumping, while also supporting the body’s weight. When people refer to the “sinew” of the hip, they are typically using an older term that modern anatomy identifies as tendons. These tendons are crucial connective tissues that facilitate movement and contribute significantly to the joint’s overall strength.
Understanding “Sinew” in the Hip
The term “sinew” is historically used to describe what is now scientifically known as a tendon. Tendons are strong, flexible bands of fibrous connective tissue composed primarily of collagen. They serve the purpose of connecting muscles to bones, acting as a bridge through which the force generated by muscle contraction is transmitted to the skeletal system. This transmission of force is what enables movement at various joints throughout the body, including the hip.
Tendons also play a role in joint stability by helping to absorb some of the impact muscles experience during movement. While remarkably strong and resistant to tearing, tendons are not highly elastic.
Major Tendon Regions of the Hip
The hip joint, a ball-and-socket joint where the head of the femur articulates with the acetabulum of the pelvis, is designed for both broad movement and substantial stability. Tendons are organized into distinct regions around this joint, each contributing to specific actions and overall function. These regions can be broadly categorized based on their anatomical position: anterior (front), posterior (back), lateral (side), and medial (inner thigh).
Each of these areas houses a unique set of tendons that enable a wide range of motions, including flexion, extension, abduction, adduction, and internal and external rotation. The collective action of these regional tendon groups ensures the hip can manage the demands of weight-bearing and mobility.
Tendons of the Anterior Hip
The anterior aspect of the hip joint contains tendons that are primarily involved in hip flexion, which is the action of bringing the thigh closer to the torso. One prominent example is the iliopsoas tendon, which represents the combined distal tendons of the iliacus and psoas major muscles. The iliacus muscle originates from the inner surface of the ilium, a large bone of the pelvis, while the psoas major originates from the lumbar vertebrae. These two muscles merge and their common tendon inserts onto the lesser trochanter, a small bony prominence on the upper inner surface of the femur (thigh bone).
Another significant tendon in this region is the rectus femoris tendon. The rectus femoris is unique among the quadriceps muscles because it crosses both the hip and knee joints. Its tendon originates from two points on the pelvis: the anterior inferior iliac spine and the supra-acetabular groove. From there, it extends downwards to insert onto the patella (kneecap) via the quadriceps femoris tendon. This tendon assists in hip flexion and also plays a role in knee extension.
Tendons of the Posterior Hip
At the posterior aspect of the hip, several important tendons contribute to movements such as hip extension, external rotation, and abduction. The gluteal muscles, which form the buttocks, have tendons that play a significant role here. The gluteus maximus, the largest of the gluteal muscles, has a broad attachment to the back of the pelvis and inserts onto the femur and the iliotibial band.
Other gluteal muscles, the gluteus medius and gluteus minimus, also have tendons located posteriorly and laterally. The gluteus medius tendon inserts onto the lateral surface of the greater trochanter, a large bony projection on the upper part of the femur. The gluteus minimus tendon, situated deeper, inserts onto the anterolateral aspect of the greater trochanter. These tendons are crucial for extending the hip and stabilizing the pelvis during activities like walking. The hamstring tendons, originating from the ischium (a lower bone of the pelvis), also contribute to hip extension and are located at the back of the thigh.
Tendons of the Lateral and Medial Hip
The lateral and medial aspects of the hip also feature distinct tendon groups, each facilitating specific movements. They are primarily responsible for hip abduction, which is moving the leg away from the midline of the body, and also contribute to medial rotation and pelvic stability.
The tensor fasciae latae (TFL) is another muscle with a tendon located on the lateral hip. It originates from the anterior part of the iliac crest and inserts into the iliotibial band (IT band). The IT band is a thick band of fascia that extends down the outer thigh to the tibia, helping with hip abduction and knee stability. On the medial side of the hip, the adductor tendons are found. These tendons connect the adductor muscles, located in the inner thigh, from the pelvis to the femur, enabling adduction—the action of pulling the leg inward towards the body’s midline.