The posterior cutaneous nerve of the thigh, also known as the posterior femoral cutaneous nerve, is a sensory nerve that arises from the sacral plexus (S1-S3). It supplies sensory innervation to the skin of the posterior thigh, lower buttock, and upper calf, as well as parts of the perineum.
Location
The posterior cutaneous nerve of the thigh originates from the sacral plexus and exits the pelvis via the greater sciatic foramen, below the piriformis muscle. It travels deep to the gluteus maximus muscle and continues down the posterior aspect of the thigh, running between the biceps femoris and semimembranosus muscles. It descends into the posterior thigh, supplying the skin, and extends to the popliteal fossa. Additionally, it has branches that extend to the skin over the lower buttock and parts of the perineum.
Structure and Anatomy
The posterior cutaneous nerve of the thigh (posterior femoral cutaneous nerve) is a sensory nerve that provides innervation to the skin on the posterior thigh, lower buttocks, and parts of the perineum. Below is a detailed description of its anatomy, including its origin, course, branches, and anatomical relationships.
Origin
The posterior cutaneous nerve of the thigh arises from the sacral plexus, specifically from the anterior rami of the S1, S2, and S3 spinal nerves. It forms alongside the other branches of the sacral plexus in the pelvic region. The nerve is composed of both dorsal and ventral divisions of these spinal nerves.
Course
Pelvic Region
The nerve exits the pelvis through the greater sciatic foramen, which is located below the piriformis muscle. This is the same route taken by the sciatic nerve and other nerves of the sacral plexus. As it passes through the greater sciatic foramen, the posterior cutaneous nerve of the thigh travels alongside the sciatic nerve but remains more superficial.
Gluteal Region
After exiting the pelvis, the nerve continues into the gluteal region, where it runs deep to the gluteus maximus muscle. It does not innervate the gluteal muscles but passes superficially over them to reach the skin of the lower buttock. In this region, it gives off several inferior clunial branches that supply the skin over the lower portion of the buttocks.
Posterior Thigh
The nerve continues its course down the posterior aspect of the thigh, running deep to the fascia lata and superficial to the muscles of the posterior compartment of the thigh, such as the biceps femoris, semitendinosus, and semimembranosus. It descends along the midline of the posterior thigh, following the same general path as the sciatic nerve but remaining more superficial.
Popliteal Fossa
As the nerve approaches the knee, it enters the popliteal fossa, the shallow depression located at the back of the knee. In this region, the nerve provides sensory branches to the skin over the upper calf. It does not enter the lower leg but terminates near the popliteal fossa.
Branches
Inferior Clunial Nerves
One of the most important branches of the posterior cutaneous nerve of the thigh is the inferior clunial nerves. These branches arise in the gluteal region and provide sensory innervation to the lower buttocks. They are responsible for the cutaneous supply of the skin over the inferior gluteal region, below the gluteal fold.
Perineal Branches
The posterior cutaneous nerve of the thigh also gives rise to perineal branches, which extend to the perineum. These branches provide sensory innervation to the skin in the perineal region, particularly in the posterior scrotal area in males or the posterior labial area in females.
Cutaneous Branches to the Posterior Thigh and Upper Calf
Throughout its course along the posterior thigh, the nerve gives off multiple small cutaneous branches that supply the skin of the posterior thigh and the upper calf. These branches are responsible for providing sensation to the skin in these regions.
Anatomical Relationships
Piriformis Muscle
The posterior cutaneous nerve of the thigh exits the pelvis just below the piriformis muscle, which is a key landmark in the gluteal region. The sciatic nerve, superior and inferior gluteal nerves, and other branches of the sacral plexus also pass through this region, making the piriformis muscle a crucial anatomical point of reference.
Gluteus Maximus Muscle
After passing through the greater sciatic foramen, the nerve travels beneath the gluteus maximus muscle, one of the largest muscles in the body. Although it passes deep to the gluteus maximus, it does not innervate this muscle but instead provides sensory innervation to the skin overlying the lower buttocks.
Posterior Thigh Muscles
As it descends through the posterior thigh, the posterior cutaneous nerve of the thigh runs superficial to the posterior compartment muscles, including the biceps femoris, semitendinosus, and semimembranosus muscles. These muscles are responsible for hip extension and knee flexion, although the nerve itself does not supply motor fibers to these muscles.
Sciatic Nerve
The posterior cutaneous nerve of the thigh runs alongside the sciatic nerve in the posterior thigh but remains more superficial. The two nerves have similar courses but serve different functions, with the sciatic nerve primarily supplying motor innervation and the posterior cutaneous nerve providing sensory innervation.
Anatomical Landmarks
- Greater Sciatic Foramen: The nerve exits the pelvis through this opening below the piriformis muscle.
- Gluteal Fold: The inferior clunial branches of the nerve supply the skin over the lower buttocks in this region.
- Posterior Midline of Thigh: The nerve runs along the midline of the posterior thigh, providing sensory innervation to the overlying skin.
- Popliteal Fossa: The nerve terminates near this region, providing sensory innervation to the upper calf.
Variations in Anatomy
In some cases, the branching pattern of the posterior cutaneous nerve of the thigh may vary, with some individuals having additional or fewer cutaneous branches. The size and distribution of its branches, such as the inferior clunial or perineal nerves, may also differ between individuals.
Termination
The posterior cutaneous nerve of the thigh terminates by providing sensory branches to the skin of the popliteal fossa and the upper calf. It does not extend into the lower leg but completes its sensory distribution in the posterior thigh and upper calf regions.
Function
The posterior cutaneous nerve of the thigh is primarily a sensory nerve that provides sensation to the skin of the lower buttocks, posterior thigh, and parts of the perineal region. Below is a detailed breakdown of its sensory functions.
Sensory Innervation of the Posterior Thigh
The posterior cutaneous nerve of the thigh supplies sensory fibers to the skin on the posterior aspect of the thigh. This region extends from the lower buttock down to the upper part of the calf. The nerve transmits sensory signals such as:
- Touch Sensation: The nerve helps detect light touch, pressure, and vibrations on the skin of the posterior thigh.
- Pain Sensation: It carries pain signals resulting from trauma, irritation, or injury to the skin in this region.
- Temperature Sensation: The nerve detects changes in temperature, allowing for sensations of warmth and cold to be processed from the posterior thigh area.
Sensory Innervation of the Lower Buttocks
A significant portion of the posterior cutaneous nerve of the thigh innervates the inferior gluteal region, also known as the lower buttocks. The nerve’s inferior clunial branches extend from the gluteal region and supply the skin over the gluteal fold, the crease where the buttocks meet the upper thigh. Functions here include:
- Sensory Feedback for Sitting: The nerve provides feedback related to pressure and touch when sitting or lying down, contributing to positional awareness.
- Pain and Temperature Sensation: The nerve carries sensory input related to pain and temperature from the lower buttock region.
Sensory Innervation of the Perineal Region
The posterior cutaneous nerve of the thigh gives off perineal branches, which provide sensory innervation to parts of the perineum. This area includes the posterior part of the scrotum in males and the labia majora in females. The sensory functions in the perineal region include:
- Touch and Pressure Sensation: The nerve detects touch and pressure stimuli in the perineum, which is important for maintaining sensory awareness of the region during daily activities like sitting.
- Pain Sensation: It carries pain signals from the perineum, helping detect irritation, trauma, or other sensations that require attention.
Proprioception and Positional Awareness
Although the posterior cutaneous nerve of the thigh is primarily a sensory nerve, it also contributes to proprioception by helping the body maintain awareness of limb position. This is particularly relevant in the thigh and buttocks during activities like walking, running, or sitting.
No Motor Function
The posterior cutaneous nerve of the thigh is exclusively a sensory nerve and does not have any motor function. It does not innervate muscles or contribute to any muscle movement or control in the thigh, buttocks, or perineal regions.
Clinical Significance
The posterior cutaneous nerve of the thigh plays a significant role in sensory innervation of the lower buttocks, posterior thigh, and perineal region. Damage, compression, or irritation of this nerve can result in various clinical symptoms.
Nerve Compression and Injury
Compression of the posterior cutaneous nerve of the thigh, often due to prolonged sitting, trauma, or surgical procedures, can lead to pain, numbness, tingling, or burning sensations in the posterior thigh and buttock areas. This is commonly seen in conditions like sciatica or nerve entrapment.
Pudendal Neuralgia
Due to its proximity to the pudendal nerve, the posterior cutaneous nerve can sometimes contribute to or exacerbate symptoms of pudendal neuralgia, a condition characterized by chronic pain in the perineal region. This pain may radiate from the buttocks and upper thigh.
Surgical Considerations
During procedures involving the hip, buttock, or posterior thigh, such as hip replacement or gluteal surgery, care must be taken to avoid damaging this nerve, as it can lead to sensory loss or chronic pain in the affected regions.
