jalkapohjan

Jalkapohja, the Finnish term for the sole of the foot, refers to the plantar aspect extending from the heel to the toes. The skin on the jalkapohja is thick and hairless, with a pronounced stratum corneum and often a visible stratum lucidum. It contains many eccrine sweat glands and relatively few hair follicles, and it is cushioned by thick fat pads under the heel and under the metatarsal heads that absorb weight-bearing shocks.

Beneath the skin lies the plantar fascia, or plantar aponeurosis, a strong band that runs from the calcaneus to the toes and helps maintain the arches and distribute load during gait. The intrinsic muscles of the sole are organized in four layers: the first layer includes abductor hallucis, flexor digitorum brevis, and abductor digiti minimi; the second layer includes quadratus plantae and lumbricals; the third layer includes flexor hallucis brevis, adductor hallucis, and flexor digiti minimi brevis; the fourth layer contains the plantar interossei and dorsal interossei. Motor and sensory innervation is provided by the medial and lateral plantar nerves, with arterial supply from the posterior tibial artery via the medial and lateral plantar arteries.

Jalkapohjan arches—the medial, lateral, and transverse arches—are formed and supported by the plantar fascia, ligaments, and the activity of the intrinsic muscles. These structures enable flexible weight bearing, shock absorption, and propulsion during standing, walking, and running.

Clinical relevance includes conditions such as plantar fasciitis, characterized by heel or medial-foot pain especially after periods of rest; fat-pad atrophy or callus formation; metatarsalgia; and plantar ulcers in individuals with diabetes. Diagnosis is typically clinical, with imaging used as needed to assess specific pathology.