List of external rotators of the body

External rotators of the body are a group of muscles that primarily work to rotate a limb or part of the body away from the midline, a movement known as external rotation or lateral rotation. These muscles are crucial for various movements and activities, including walking, running, and throwing. This article provides an overview of the primary external rotators found in the human body, focusing on their anatomy, function, and significance.

External Rotators of the Hip

The hip joint is one of the main areas where external rotation occurs, facilitated by several key muscles:

• Piriformis: Originates from the sacrum and inserts on the greater trochanter of the femur. It is known for its role in rotating the hip externally and abducting the thigh when the hip is flexed.
• Gemellus Superior and Gemellus Inferior: These muscles work together with the Obturator Internus and Obturator Externus to rotate the thigh laterally.
• Obturator Internus: Lies deep within the pelvis and is a powerful external rotator of the hip.
• Obturator Externus: This muscle also plays a significant role in the external rotation of the thigh.
• Quadratus Femoris: It is located inferior to the Gemelli and Obturator Internus and assists in lateral rotation and adduction of the thigh.

External Rotators of the Shoulder

The shoulder joint also relies on external rotators for its wide range of motion:

• Infraspinatus: Part of the rotator cuff muscles, it covers the majority of the scapula's infraspinous fossa and is a potent external rotator of the shoulder.
• Teres Minor: Also a member of the rotator cuff, it assists in the lateral rotation of the arm and adds stability to the glenohumeral joint.

Other External Rotators

While the hip and shoulder contain the primary external rotators, other parts of the body also have muscles that facilitate external rotation:

• Sartorius: Although primarily involved in flexing, abducting, and externally rotating the hip, it can assist in external rotation when the hip is flexed.
• Biceps Brachii: Known mainly for its role in the flexion of the elbow and supination of the forearm, the long head of the biceps brachii can also assist in shoulder external rotation.

Function and Significance

External rotators are crucial for the stability and mobility of the joints they serve. In the hip, they allow for the outward turning of the leg, which is essential for activities such as walking, running, and changing direction. In the shoulder, external rotation is vital for reaching overhead, throwing, and performing various arm movements.

Conclusion

Understanding the anatomy and function of the external rotators of the body is essential for both medical professionals and individuals looking to maintain or improve their physical health. These muscles play a significant role in the movement and stability of the hip and shoulder joints, contributing to the body's overall mobility and functionality.