Patients with lower back pain due to irritation of the L5 and S1 nerve roots may have difficulty with turning the foot inward toward the midline (inversion). Usually with foot inversion, the sole of the foot is turned toward the midline of the body.
Muscles that turn the foot inward are primarily supplied by the L5 nerve roots. The foot inverting muscles supplied by the posterior tibial nerve (L5, S1) include:
- tibialis posterior
- flexor digitorum longus
- flexor hallucis longus
- gastrocnemius (medial and lateral)
- soleus
These muscles in addition to foot inversion also cause plantar flexion of the foot.
The foot inverting muscles supplied by the deep peroneal nerve include:
- tibialis anterior (L4, L5)
- extensor hallucis longus (L5, S1)
These muscles in addition to foot inversion also cause dorsiflexion of the foot.