Patients with lower back pain due to irritation of the L5 and S1 nerve roots can present first with pain in the ankle, foot and toes. Patients with lower back pain due to irritation of the L5 and S1 nerve roots can present first with pain in the ankle, foot and toes. Muscles that perform flexion of the toes are supplied by the L5 and S1 nerve roots. When these muscles are in pain and spasm, performing plantar flexion of the toes can result in the cramps in the toes muscles causing the toes to go down into flexion. This can be quite painful.
Muscles that flex all the toes except the big toe:
- Flexor digitorum longus (supplied by the posterior tibial nerve L5, S1). This muscle will flex the toes at the distal interphalangeal joints.
- Flexor digitorum brevis (supplied by the medial plantar nerve, S1, S2). This muscle will flex the metatarsophalangeal and proximal interphalangeal joints.
- Lumbricals and interossei (supplied by the medial and lateral plantar nerves namely S1, S2. These muscles will flex the metatarsophalangeal joints and extend at the interphalangeal joints.
Other muscles that assist in flexion of the other toes except the big toe are:
- flexor digiti quinti brevis (supplied by the lateral plantar nerve S1, S2)
- abductor digiti quinti (supplied by the lateral plantar nerve S1, S2)
Muscles that flex the big toe are:
- Flexor hallucis brevis: supplied by the medial plantar nerve (S1, S2). Flexes the great toe at the metatarsophalangeal joint.
- Flexor hallucis longus: supplied by the posterior tibial nerve (L5, S1). Flexes the great toe at the interphalangeal joint.
Other muscles that assist in flexion of the big toe are:
- abductor hallucis (supplied by the medial plantar nerve, S1, S2)
- adductor hallucis (supplied by the lateral plantar nerve, S1, S2).