Tendon of fibularis longus

The tendon of the fibularis longus (Peroneus longus tendon; FL) originates from the distal myotendinous junction of the fibularis longus muscle, which is located just above the level of the lateral malleolus in the lower leg. The tendon then passes posterior to the lateral malleolus, traveling through the superior and inferior peroneal retinacula, and courses along the lateral aspect of the calcaneus. It then makes a sharp turn medially, passing through a groove on the plantar surface of the cuboid bone (the cuboid tunnel), before crossing the sole of the foot obliquely to insert primarily onto the tuberosity of first metatarsal bone and the medial cuneiform.

Anatomical studies have shown that while the attachment to the base of the first metatarsal is consistent, a slip to the medial cuneiform is present in the majority of specimens, and additional slips to other metatarsals or the neck of the first metatarsal may occur as anatomical variants.

The tendon is stabilized by the superior and inferior peroneal retinacula and is closely associated with the os peroneum, a sesamoid bone that may be present within the tendon near the cuboid tunnel. The fibularis longus tendon plays a key role in maintaining the transverse and longitudinal arches of the foot and contributes to eversion and plantarflexion of the foot.

Common mnemonics

• “Brevis before Longus” A simple phrase to recall that the brevis tendon lies in front of the longus as they pass behind the lateral malleolus.

• “B over L” (Brevis over Longus) Reinforces the vertical relationship: brevis is superficial/anterior, longus is deep/posterior.

• Bruce Lee

• “BLT – Brevis Longus Tendons” Some use this food-related mnemonic (like a BLT sandwich) to remember the brevis comes first, then longus.