Lower limb

Fibularis tertius

Musculus fibularis tertius

Origin

Distal anterior surface of the fibula and the interosseous membrane

Insertion

Dorsal base of the fifth metatarsal bone

Function

Dorsiflexion and eversion of the foot

Innervation

Deep fibular (peroneal) nerve, L5-S1

Movement & chain

Functionally regarded as part of extensor digitorum longus (sometimes considered a split-off from it) and helps lift the foot during the swing phase.

Palpation

The tendon is sometimes weakly palpable on the dorsolateral foot, just in front of the lateral malleolus, during active dorsiflexion with eversion.

Clinical

Not present in everyone (absent in approximately 5-10% of people); its absence generally has no functional consequences.

Segmental innervation

L5-S1, tested together with the other dorsiflexors of the foot.

In clinical practice

Diabetic foot inspection and pressure ulcer prevention; monitor for friction points from footwear or bedding and ensure correct anti-embolism stocking fit.

Region in the model

Lower limb