Gluteus medius

While the powerful hip movements originate from the all-so-strong gluteus maximus, the stability of the hip and pelvis is entrusted to another important fan-shaped muscle – the gluteus medius. 

Since it provides dynamic, rotational, and compressive stability to the hip joint and keeps the femoral head in place, just like the rotator cuff muscles do for the shoulder, it is called as the rotator cuff of the hip. 

Gluteus medius is one of the three muscles of the gluteal region. It makes up the intermediate layer of muscle between the gluteus maximus and minimus. It is the primary abductor muscle. 

This muscle plays a crucial role in pelvic control, gait efficiency, and lower limb alignment. Weakness or dysfunction here can trigger a domino effect of biomechanical issues throughout the kinetic chain.

Anatomy

Proximal attachment:

Proximally, the gluteus medius has a wide attachment to the external or outer surface of the ilium between the anterior and posterior gluteal lines, below the iliac crest.

Distal attachment:

Then distally, this fan-shaped muscle converges and attaches to the lateral surface of the greater trochanter of the femur.

Nerve innervation:

The gluteus medius is innervated by the superior gluteal nerve, a branch of the sacral plexus (L5, S1, S2).

Blood supply:

This muscle gets a good blood supply from the superior gluteal artery, a branch of the internal iliac artery. 

Function

The gluteus medius is a prime mover for hip abduction and a key stabiliser of the hip and pelvis. It is mainly known for its exceptional role in providing dynamic stability, which is essential for activities like walking, running, jumping, climbing stairs, and standing on a single leg.

Concentric (shortening) action:

Standard mover action:(distal attachment moving towards proximal) 

  • All the fibres will help in the abduction of the thigh at the hip joint.  
  • The anterior fibres will pass anterior to the hip joint, thereby helping in flexion and internal rotation at the hip joint. 
  • The posterior fibres cross the hip joint posteriorly, thereby helping in extension and external rotation of the hip joint. 

Reverse mover action:(proximal attachment moving towards distal) 

  • All the fibres of this muscle depress the same side pelvis. 
  • Anterior fibres will assist in the anterior pelvic tilt and ipsilateral pelvic rotation. 
  • Posterior fibres will assist in the posterior pelvic tilt and contralateral pelvic rotation.

Eccentric (lengthening) action:

It restrains and controls the adduction of the hip joint, as well as the flexion, internal rotation by the posterior fibres and extension, external rotation by the anterior fibres.  

Isometric function:

  • Isometric action of the gluteus medius will stabilise the pelvis, hip joint directly. 
  • Since it resists medial rotation of the thigh, thereby preventing medial rotation of the entire limb and stabilises the subtalar joint.

What is the difference between the gluteus maximus and the gluteus medius?

The gluteus maximus and gluteus medius are both parts of the gluteal muscle group. Though both muscles act primarily on the hip joint, they differ in their structure and their function around the hip joint.

Difference in Anatomy:

The gluteus maximus is the largest and most superficial of the three gluteal muscles, forming the bulk and rounded contour of the buttock. It is a large, quadrangular muscle that originates from the posterior ilium, sacrum, and coccyx, and inserts into the iliotibial band and gluteal tuberosity of the femur. 

On the other hand, we have the gluteus medius, which lies deep to the maximus. This fan-shaped muscle originates from the outer surface of the ilium and inserts onto the lateral surface of the greater trochanter.

They differ in nerve supply also, for the gluteus maximus, it is the inferior gluteal nerve, and for the gluteus medius, it is the superior gluteal nerve. 

Difference in function:

The primary function of the gluteus maximus is extension and external rotation of the hip, which makes it play a major role in powerful movements in everyday and sports activities, such as rising from a chair, climbing stairs, and sprinting. It is well known for its force generation capacity. 

Coming to the Gluteus medius, its main function is hip abduction and pelvic stabilisation during single-leg stance, walking, and running. The anterior fibres of the gluteus medius assist in internal rotation and flexion of the hip, while the posterior fibres assist in external rotation and extension. 

While the gluteus maximus stands out for its power production capacity, the gluteus medius provides precision and stability, preventing pelvic drop during gait. 

Difference in clinical aspect:

Clinically, weakness of the gluteus maximus causes reduced hip extension strength, which may be precipitated by low-back pain or knee pain at times, while weakness of the gluteus medius results in pelvic instability and the characteristic Trendelenburg gait.

What happens when the gluteus medius is weak?

The gluteus medius is a crucial muscle for maintaining hip and pelvic stability. When it becomes weak, the hip loses its main stabiliser. This results in pelvic drops on the opposite side during walking or standing on one leg, called a Trendelenburg sign. When both the gluteus medii are weak, then the person will have a waddling gait due to poor hip and pelvis stability on both sides. 

From a biomechanical standpoint, a weak gluteus medius cannot control adduction and internal rotation of the femur, which makes the knee move medially. This, in turn, increases strain on the patellofemoral joint, IT band, and ACL, leading to patellofemoral pain syndrome, IT band syndrome, and increasing the risk of ACL injury.

Also, to compensate for the weak gluteus medius, other muscles like the tensor fascia latae, quadratus lumborum and hamstrings will work more to maintain hip stability. Over a period, this can cause and even result in lower back pain.

From a functional standpoint, weakness of the gluteus medius can reflect as difficulty in climbing stairs, performing any single-leg tasks, and early fatigue during lower limb activities, including balace task, or standing. As the person ages, this increases the risk of fall dur to poor stability.

However, strengthening the gluteus medius with appropriate exercises and adequate load can prevent many of these issues. Mentioned below are a few exercises among many for activating the gluteus medius: 

  • Isometric exercises: single-leg stance, side-lying abduction hold, and clamshell isometric hold. 
  • Resistance training: side-lying abduction, cable abduction, lateral band walks, and side-plank leg lift. 
  • Eccentric exercises: controlled-step down, lateral step down, and lateral lunges.