Lateral Plantar Nerve

The lateral plantar nerve is a branch of the tibial nerve, which arises from the sciatic nerve. It is located in the foot and serves as the primary nerve for the lateral aspect of the plantar surface. The nerve emerges from the tibial nerve near the medial malleolus (the bony prominence on the inner side of the ankle), runs beneath the flexor retinaculum, and enters the foot through the tarsal tunnel. It then courses along the lateral side of the sole, innervating the muscles and skin of the lateral plantar region. The lateral plantar nerve divides into superficial and deep branches as it progresses through the foot.

Structure and Anatomy

The lateral plantar nerve is one of the two terminal branches of the tibial nerve, the other being the medial plantar nerve. It plays a crucial role in innervating the lateral aspect of the foot. Below is a detailed description of the anatomy of the lateral plantar nerve.

Origin

The lateral plantar nerve arises from the tibial nerve, which itself is a branch of the sciatic nerve. The tibial nerve splits into the lateral and medial plantar nerves after it passes behind the medial malleolus, in the area known as the tarsal tunnel.

Course and Pathway

• Proximal Course: After branching from the tibial nerve, the lateral plantar nerve runs beneath the flexor retinaculum along with the medial plantar nerve and enters the plantar aspect of the foot. As it courses forward, it travels deep to the abductor hallucis muscle and alongside the lateral plantar artery.
• Midfoot: In the midfoot, the lateral plantar nerve passes between the flexor digitorum brevis and the quadratus plantae muscles, continuing laterally toward the lateral side of the sole.
• Distal Course and Branching: As the nerve progresses further, it divides into superficial and deep branches:
• • Superficial Branch: The superficial branch travels toward the lateral side of the foot, providing innervation to the skin and some muscles.
  • Deep Branch: The deep branch dives deep into the musculature of the foot, running alongside the lateral plantar artery and innervating deep structures of the foot.

Branches of the Lateral Plantar Nerve

• Superficial Branch: This branch of the lateral plantar nerve is primarily cutaneous and muscular. It innervates the lateral side of the foot, providing sensory innervation to the skin. It also supplies motor innervation to some small muscles of the foot, particularly the flexor digiti minimi brevis and interossei muscles.
• Deep Branch: The deep branch is more muscular and follows a deep pathway along the lateral aspect of the foot. It innervates deeper muscles, such as the adductor hallucis, the remaining interossei muscles, and the lumbricals.

Relationship to Neighboring Structures

• Flexor Retinaculum: The lateral plantar nerve passes beneath the flexor retinaculum, a thick band of connective tissue that holds the tendons, nerves, and blood vessels in place as they pass behind the medial malleolus and into the sole of the foot.
• Lateral Plantar Artery: The nerve runs alongside the lateral plantar artery, which provides vascular supply to the lateral side of the foot. The close proximity of the nerve and artery is important for surgical procedures and when considering pathologies that may affect the vascular and nervous supply to the foot.
• Muscles: The lateral plantar nerve runs deep to the abductor hallucis and between the flexor digitorum brevis and quadratus plantae muscles. It supplies motor branches to many intrinsic muscles of the foot, influencing the movement of the toes and stabilization of the foot during walking.

Distribution

• Sensory Innervation: The lateral plantar nerve provides sensory innervation to the lateral part of the sole of the foot, including the skin over the lateral three and a half toes (shared with the medial plantar nerve).
• Motor Innervation: The nerve innervates several intrinsic muscles of the foot, including the quadratus plantae, flexor digiti minimi brevis, abductor digiti minimi, and the lumbricals (laterally), as well as the plantar and dorsal interossei.

Anatomical Variations

The branching pattern and the exact course of the lateral plantar nerve can vary between individuals. Some people may have slight differences in how the nerve divides into its superficial and deep branches, or in the distribution of its motor and sensory innervation. Additionally, variations in the relationship between the lateral plantar nerve and the lateral plantar artery may occur, which can have implications for surgical interventions in the region.

Function

The lateral plantar nerve is responsible for both motor and sensory functions in the lateral aspect of the foot. As a major branch of the tibial nerve, it innervates the skin and several muscles of the foot, contributing to its sensory perception and movement, particularly for the lateral toes and sole. Below is a detailed description of its motor and sensory functions.

Motor Function

The lateral plantar nerve provides motor innervation to several intrinsic muscles of the foot, which are essential for controlling the movement of the toes and stabilizing the foot during walking and standing.

• Abductor Digiti Minimi: The lateral plantar nerve innervates the abductor digiti minimi muscle, which is responsible for the abduction of the little toe (moving the fifth toe away from the midline of the foot). This helps maintain balance, especially during lateral movements of the foot.
• Flexor Digiti Minimi Brevis: This muscle, also innervated by the lateral plantar nerve, assists in the flexion of the fifth toe at the metatarsophalangeal joint, allowing the toe to curl and press against the ground during walking.
• Quadratus Plantae: The lateral plantar nerve innervates the quadratus plantae muscle, which aids in the function of the flexor digitorum longus. It helps align the pull of the flexor digitorum longus, improving the efficiency of toe flexion, particularly in the lateral toes. This is important for pushing off during the propulsion phase of walking.
• Lumbricals (Lateral): The lateral plantar nerve innervates the lateral lumbricals, which are small muscles located between the toes. These muscles help flex the metatarsophalangeal joints and extend the interphalangeal joints of the lateral toes, contributing to the fine motor control of toe movements.
• Interossei Muscles (Plantar and Dorsal): The lateral plantar nerve innervates the plantar and dorsal interossei muscles, which are responsible for abduction and adduction of the toes. The dorsal interossei abduct the toes (spread them apart), while the plantar interossei adduct the toes (bring them together). These muscles play a crucial role in maintaining toe alignment and stability, especially during walking.
• Adductor Hallucis: The deep branch of the lateral plantar nerve innervates the adductor hallucis muscle, which is responsible for adducting the big toe (bringing it closer to the second toe). This helps with maintaining proper foot alignment and stability during activities such as walking, running, and balancing.

Sensory Function

The lateral plantar nerve also plays a critical role in providing sensory innervation to the skin of the lateral aspect of the foot and toes. This sensory function is crucial for detecting tactile stimuli, pressure, and temperature, which helps in maintaining balance and protection of the foot.

• Lateral Sole Sensation: The lateral plantar nerve supplies sensory innervation to the lateral portion of the sole of the foot, covering the region around the fifth toe and the outer border of the foot. Sensory signals from this area help the body respond to external stimuli, such as pressure or temperature, which is important for adjusting posture and foot positioning during walking and standing.
• Lateral Three and a Half Toes: The lateral plantar nerve provides sensory innervation to the lateral three and a half toes, covering the fourth and fifth toes and the lateral half of the third toe. This sensory input helps in detecting pressure changes and other tactile sensations, which are important for foot mechanics and balance during movement.
• Superficial Branch Sensory Input: The superficial branch of the lateral plantar nerve provides cutaneous (sensory) innervation to the skin on the lateral side of the foot and the skin of the fifth toe. This branch allows the foot to respond to environmental changes, protecting the skin and underlying structures from injury by detecting potentially harmful stimuli like excessive pressure or heat.

Role in Gait and Balance

The lateral plantar nerve is essential for maintaining proper foot mechanics during walking and standing. The motor innervation provided by the nerve allows for controlled movement of the toes, especially the lateral toes, which contribute to balance and propulsion during gait.

• Toe Flexion and Push-Off: The flexor muscles innervated by the lateral plantar nerve, including the flexor digiti minimi brevis and quadratus plantae, allow for the flexion of the lateral toes, which is essential for the push-off phase of gait. This ensures that the body can propel itself forward efficiently.
• Lateral Foot Support: The nerve’s innervation of the abductor digiti minimi and other lateral muscles helps to support the lateral border of the foot, which is particularly important when the body shifts its weight laterally, such as when walking on uneven surfaces.
• Toe Abduction and Adduction: The interossei muscles, controlled by the lateral plantar nerve, play a critical role in stabilizing the toes during gait by providing abduction and adduction movements. This function prevents the toes from splaying excessively or collapsing inward, maintaining proper foot alignment.

Coordination with the Medial Plantar Nerve

The lateral plantar nerve works in conjunction with the medial plantar nerve to ensure comprehensive innervation of the plantar surface of the foot. While the medial plantar nerve is responsible for innervating the medial portion of the foot and the first three toes, the lateral plantar nerve covers the lateral half of the third toe and beyond. Together, these nerves provide both motor and sensory control over the entire plantar surface, contributing to precise foot movement and sensation.

Clinical Significance

The lateral plantar nerve plays a critical role in both motor and sensory functions of the foot, and its dysfunction can lead to various clinical conditions. Injury or compression of the lateral plantar nerve can result in lateral plantar neuropathy, which may cause pain, numbness, tingling, or weakness in the lateral aspect of the foot and fourth and fifth toes. This condition can affect activities like walking and balancing, as the nerve innervates key muscles that control toe movement and foot stabilization.

Tarsal tunnel syndrome, a condition in which the tibial nerve or its branches (including the lateral plantar nerve) are compressed in the tarsal tunnel, can also impact the lateral plantar nerve, leading to symptoms such as pain, burning, or tingling in the sole of the foot. Early diagnosis and treatment are essential to prevent long-term complications and to maintain proper foot function.