1st sacral spinal nerve (S1)

Function

• plantar flexion of foot
• sensory lateral foot, posterior leg

Innervation

• foot evertors
• gastrocnemius

Pathology

Referred pain:

• L5 & S1 -> lateral or posterior calf
• S1 -> heel & lateral foot

Physical examination

• walking on toes test motor function at S1
• the ankle jerk tests motor function at S1
• light touch in the lateral foot tests sensory function at S1.

More general terms

• sacral spinal nerve

Additional terms

• dermatome
• myotome