The superior gluteal nerve is a motor nerve that arises from the sacral plexus, specifically from the ventral rami of the L4, L5, and S1 spinal nerves. It is responsible for innervating key muscles in the gluteal region, including the gluteus medius, gluteus minimus, and tensor fasciae latae.
Location
The superior gluteal nerve exits the pelvis through the greater sciatic foramen, passing above the piriformis muscle. It then travels laterally and superiorly in the gluteal region, running between the gluteus medius and gluteus minimus muscles. The nerve courses with the superior gluteal artery and vein, supplying motor innervation to the muscles of the lateral hip. It remains confined to the deep layers of the gluteal region and does not extend into the lower limb.
Structure and Anatomy
The superior gluteal nerve is a key motor nerve in the gluteal region, responsible for innervating several important muscles that contribute to hip movement and stabilization. Below is a detailed description of its anatomy, including its origin, course, anatomical relationships, and branches.
Origin
The superior gluteal nerve originates from the sacral plexus, specifically from the ventral rami of the L4, L5, and S1 spinal nerves. These nerves converge in the pelvic region to form the superior gluteal nerve. The sacral plexus, located on the posterior wall of the pelvis, gives rise to several important nerves that innervate the lower limb, including the superior and inferior gluteal nerves.
Course
Pelvic Region
After originating from the sacral plexus, the superior gluteal nerve exits the pelvis through the greater sciatic foramen, which is located above the piriformis muscle. This is a distinguishing feature, as the superior gluteal nerve is one of the few structures that pass above the piriformis muscle, unlike the sciatic and inferior gluteal nerves, which exit below the piriformis.
Gluteal Region
Once the superior gluteal nerve exits the pelvis, it travels laterally and superiorly in the deep layers of the gluteal region. It runs between the gluteus medius and gluteus minimus muscles, supplying motor innervation to both muscles as it progresses. It follows a path parallel to the superior gluteal artery and vein, which also pass above the piriformis muscle and supply blood to the same region.
As the nerve runs laterally, it moves toward the tensor fasciae latae muscle, another important structure that it innervates.
Anatomical Relationships
Piriformis Muscle
The superior gluteal nerve exits the pelvis through the greater sciatic foramen above the piriformis muscle, making this muscle a key anatomical landmark. The piriformis muscle separates the structures that exit the greater sciatic foramen into those that pass above it (including the superior gluteal nerve) and those that pass below it (such as the sciatic nerve and inferior gluteal nerve).
Gluteus Medius and Gluteus Minimus Muscles
The superior gluteal nerve is primarily located between the gluteus medius and gluteus minimus muscles. As it travels between these two muscles, it provides motor innervation to both. The gluteus medius and minimus are essential for hip abduction and stabilization, and the superior gluteal nerve is responsible for their activation.
Tensor Fasciae Latae Muscle
As the superior gluteal nerve continues its lateral course, it also innervates the tensor fasciae latae muscle, which lies anterior to the hip and is involved in hip abduction and medial rotation. The nerve reaches this muscle after innervating the gluteus medius and minimus.
Superior Gluteal Artery and Vein
The superior gluteal nerve runs parallel to the superior gluteal artery and vein, which provide vascular supply to the gluteal muscles. These vessels follow the same general path as the nerve, exiting the pelvis through the greater sciatic foramen above the piriformis muscle and continuing laterally into the gluteal region.
Branches
The superior gluteal nerve gives off several muscular branches as it travels through the gluteal region. These branches are responsible for innervating the gluteus medius, gluteus minimus, and tensor fasciae latae muscles.
Branches to the Gluteus Medius
As the superior gluteal nerve courses between the gluteus medius and minimus, it gives off multiple branches that supply motor innervation to the gluteus medius muscle. These branches spread out across the muscle to ensure that it receives proper innervation for coordinated movement.
Branches to the Gluteus Minimus
Similarly, the nerve provides branches to the gluteus minimus muscle, which lies deep to the gluteus medius. The gluteus minimus plays a role in hip abduction and medial rotation, and the superior gluteal nerve ensures its proper function.
Branch to the Tensor Fasciae Latae
After supplying the gluteus medius and minimus, the superior gluteal nerve continues laterally to innervate the tensor fasciae latae muscle, which is located on the lateral aspect of the thigh. This muscle contributes to hip abduction and stabilization of the knee joint.
Anatomical Landmarks
- Greater Sciatic Foramen: The nerve exits the pelvis through this foramen, passing above the piriformis muscle.
- Gluteus Medius and Minimus Muscles: The nerve runs between these two muscles, innervating them as it travels.
- Tensor Fasciae Latae: The nerve terminates by innervating this muscle on the lateral aspect of the thigh.
Variations in Anatomy
The course of the superior gluteal nerve is relatively consistent in most individuals, though minor anatomical variations may occur. In some cases, the branches of the nerve may differ slightly in their distribution, but the general path remains consistent, with the nerve passing above the piriformis and running between the gluteus medius and minimus.
Termination
The superior gluteal nerve terminates by innervating the tensor fasciae latae muscle. After giving off its final branches to this muscle, the nerve does not extend beyond the gluteal region and does not supply structures below the hip.
Function
The superior gluteal nerve is a motor nerve that plays a critical role in controlling key muscles in the gluteal region, including the gluteus medius, gluteus minimus, and tensor fasciae latae. These muscles are essential for hip movement, stabilization of the pelvis, and balance during activities such as walking, running, and standing. Below is a detailed explanation of the functions of the superior gluteal nerve.
Motor Innervation of the Gluteus Medius
The superior gluteal nerve provides motor innervation to the gluteus medius muscle, which is one of the primary abductors of the hip. The gluteus medius is located on the lateral aspect of the hip and performs several key actions:
Hip Abduction
The gluteus medius, controlled by the superior gluteal nerve, is responsible for abducting the hip, which is the movement of the leg away from the midline of the body. This function is crucial in:
- Walking: During the stance phase of walking, the gluteus medius prevents the pelvis from tilting to the unsupported side.
- Running: The muscle helps stabilize the pelvis as the body moves through space.
- Side-stepping movements: Hip abduction is important in actions such as side lunges or stepping sideways.
Pelvic Stabilization
The gluteus medius, innervated by the superior gluteal nerve, is also crucial for maintaining pelvic stability during activities that involve balancing on one leg, such as walking or running. The muscle helps prevent hip drop on the unsupported side during the stance phase of walking, ensuring a steady gait.
Assistance in Hip Internal and External Rotation
The superior gluteal nerve’s control of the gluteus medius allows it to assist in hip rotation:
- The anterior fibers of the gluteus medius assist in internal rotation of the hip.
- The posterior fibers contribute to external rotation of the hip.
Motor Innervation of the Gluteus Minimus
The superior gluteal nerve also innervates the gluteus minimus muscle, which lies deep to the gluteus medius. The gluteus minimus works alongside the gluteus medius to perform similar actions:
Hip Abduction
The gluteus minimus, like the gluteus medius, contributes to hip abduction, helping to move the leg away from the midline. This action is particularly important in stabilizing the pelvis during walking and maintaining balance during other movements.
Hip Internal Rotation
The gluteus minimus, controlled by the superior gluteal nerve, plays a key role in internally rotating the hip, which involves rotating the thigh inward. This function is important during activities such as walking and running, where the leg needs to rotate inward to stabilize the body during movement.
Pelvic Stability
Similar to the gluteus medius, the gluteus minimus also plays a role in pelvic stabilization, particularly during single-leg stance activities, helping to prevent excessive tilting of the pelvis when weight is shifted to one leg.
Motor Innervation of the Tensor Fasciae Latae
The superior gluteal nerve innervates the tensor fasciae latae muscle, which is located on the lateral aspect of the thigh. This muscle plays a role in stabilizing both the hip and the knee.
Hip Abduction and Flexion
The tensor fasciae latae, under the control of the superior gluteal nerve, assists in hip abduction alongside the gluteus medius and minimus. Additionally, it helps in hip flexion, raising the thigh toward the abdomen, which is important in movements like walking, running, and climbing stairs.
Medial Rotation of the Hip
The tensor fasciae latae also contributes to medial (internal) rotation of the hip, an action that involves rotating the thigh inward.
Stabilization of the Knee
Through its attachment to the iliotibial (IT) band, the tensor fasciae latae helps stabilize the knee joint during walking and running. The superior gluteal nerve ensures the proper functioning of this muscle, which keeps the IT band taut and provides lateral knee support.
No Sensory Function
The superior gluteal nerve is a purely motor nerve and does not carry any sensory fibers. Sensory innervation to the skin over the gluteal region is provided by other nerves, such as the posterior cutaneous nerve of the thigh and the clunial nerves.
Clinical Significance
The superior gluteal nerve is crucial for the proper functioning of the gluteus medius, gluteus minimus, and tensor fasciae latae muscles, which are responsible for hip abduction, pelvic stability, and balance. Injury to this nerve can lead to significant clinical issues:
Superior Gluteal Nerve Injury
Damage to the superior gluteal nerve can result from trauma, surgical procedures (such as hip replacement), or compression, leading to weakness or paralysis of the gluteal muscles. This results in Trendelenburg gait, a characteristic waddling gait where the pelvis tilts toward the unsupported side during walking.
Pelvic Instability
A weak or damaged superior gluteal nerve impairs the gluteus medius and minimus muscles, causing pelvic instability during walking, running, or standing on one leg. This makes balance and mobility difficult, especially during single-leg stance.
Hip Pain and Dysfunction
Superior gluteal nerve damage may cause hip weakness and contribute to conditions like hip dysplasia or chronic hip pain, especially when the muscles responsible for stabilizing the hip are compromised.
