Plantar

Plantar (pronounced plan-ter)

In anatomy and zoology, of or relating to the sole of the foot.

1706: From the Latin plantāris (pertaining to the sole of the foot), from planta (sole of the foot) from a nasalized form of the primitive Indo-European root pletə- or plat- (to spread) an extension of the root pele- (flat; to spread).  Related were the Sanskrit prathati (spreads out), the Hittite palhi (broad), the Ancient Greek platys (broad, flat), the Lithuanian platus (broad), the German Fladen (flat cake), the Old Norse flatr (flat), the Old English flet (floor, dwelling) and the Old Irish lethan (broad).  The Latin planta may be analysed as plant +‎ -ar.  The –ar suffix was from Latin -āris (of, pertaining to) and was appended to nouns to create adjectives.  The -aris suffix was a form of -ālis with dissimilation of -l- to -r- after roots containing an l (the alternative forms were -ālis, -ēlis, -īlis & -ūlis); it was used to form adjectives, usually from noun, indicating a relationship or a "pertaining to".  The exact origin of the Latin planta (which in addition to meaning (1) “sole of the foot” could be used in the sense of (2) any vegetable production that serves to propagate the species; a sprout, shoot, twig, sprig, sucker, graft, scion, slip, cutting or (3) a young tree, a shrub that may be transplanted; a set) is uncertain.  It was from either (1) the Proto-Italic plāntā, from the primitive Indo-European pléh-n̥t-eh, from pleh- (flat) or (2) the Proto-Italic plānktā, from the primitive Indo-European pl̥hnk or gteh, from plehk- & plehg- (to strike, fast).  In anatomy, the derived terms include plantar fascia (the thick connective tissue which supports the arch of the foot) and plantar fasciitis (a painful inflammation of the plantar fascia.  The term plantar wart (apparently sometimes initially misunderstood by patients as “planter’s wart”) describes a wart which occurs on the sole of the foot or the toes.  The medical Latin is verruca plantaris.  Plantar is an adjective.

Plantar flexion and dorsiflextion

Lindsay Lohan, plantaflexing.

Plantar flexion refers to the movement of the foot when it is bent at the ankle away from the body, accomplished by flexing muscles in the calf, ankle, and foot.  In normal range of human activity, the range of motion is usually between 20-50^o, a commons example being depressing a car’s accelerator (throttle) pedal. Or even the mere act of walking.  The word “flexion” is used by anatomists and others to describe the movement of many body parts.  The notion of flexing at the knee or elbow is well understood in everyday life and technically, flexion is the decreased angle at a joint between two or more bones.  In the common act of bending the elbow from a straightened position, the angle decreases between the humerus and the radius and ulna of the forearm.  Plantar flexion is defined usually as the decreased angle between the plantar side of the foot and the back of the tibia at the tibiotalar joint (better known as the ankle) and can be visualized as the bending of the sole of the foot down where the toes are moving down and away from the body.  Done deliberately in exaggerated form it can feel unnatural but having one’s toes point downwards is something inherent to human movement, the activities (as well as using a car’s throttle pedal) including bending the foot during walking (propelling the mass of the body forward as it pushes off the ground) and standing on one’s tip toes which reaching for something in a high place.

Lindsay Lohan, dorsiflextion to the left, plantar flexion to the right.

The companion movement is dorsiflexation, an upward bending which, although applied most often to the foot, other body parts such as hands or digits (fingers) can be said to dorsiflex.  Dating from the early nineteenth century, dorsiflexion was a creation which appeared first in the literature of the early-modern science of anatomy.  The construct was dorsi (from the Middle English dorsal or dorsale from the Medieval Latin dorsālis (of or relating to the back)) + flex (from the Latin flexiō (genitive flexiōnis), from flectō (I bend, curve), from the Proto-Italic flektō, of uncertain origin and unknown in other Indo-European cognates) + -ion (the Latin suffix denoting action or condition).  The –ion suffic was from the Middle English -ioun, from the Old French -ion, from the Latin -iō (genitive -iōnis).  It was appended to a perfect passive participle to form a noun of action or process, or the result of an action or process.  Dorsiflexion is also a movement associated with the multiple joints.  The definition is of an action in which induces a decreased angle between the dorsal side of the body part and the bone or bones that are proximal to the body.  When one’s wrist is bent and the back of the hand is moving towards the body, that is an act of dorsiflexion and when the toes are pointed up or raised backward toward the body, this is also dorsiflexion so, using the feet as an illustrative example, plantar flexion and dorsiflextion can be understood as opposite movements at the ankle joint (both obviously being associated with flexion). That means the essence of the difference is the location of the foot doing the bending away from the ankle joint: If the toes rise as the ankle bends, it’s dorsiflexion while if the toes tend downwards, it’s a plantar flex.

Lindsay Lohan, plantar flexion to the left, dorsiflextion to the right.

Although the term (plantar flex) and word (dorsiflex) refer to variations of the same movement, the practice has always been to use a compound form only for the latter although the mechanics of the etymology is the same in that plantar flex references the sole of the foot and dorsiflex the back.  Perhaps counter-intuitively, the upper surface of a foot (the dorsal surface) is, to an anatomist, the back, a convention of use more familiar when used as the “back of the hand”.  Anatomists recommend imaging the dorsal fin of the shark as a memory trick, something associated with the “back side of an animal”. Consider a dorsal fin on a shark which is located on the back side of the shark. If the foot was a four-legged animal, the dorsal side would be the top of the foot. Likewise, if the hand was held out straight, the back side of the hand is called the dorsal side.  Interestingly, by convention, despite the obvious etymological connections, dorsiflex is the universal form while plantarflex, although a correct alternative spelling, is rarely seen outside of technical literature.