Action of FDB?

Action of FDB?

• A. Flexion of DIP joints
• B. Plantarflexion of PIPJ and MTPJ
• C. Dorsiflexion of MTPJ
• D. Abduction of toes

Answer: (B)

The action of the Flexor digitorum brevis is to bend the proximal joints of the toes. It pulls on the middle phalanges to flex the proximal interphalangeal joints (toe PIPs) and also helps curl the toes by flexing the metatarsophalangeal joints (MTPs). That makes the description of plantarflexion at the PIP and MTP joints the best match for its effect. It does not flex the distal interphalangeal joints (that’s the flexor digitorum longus), nor does it cause toe abduction or MTP dorsiflexion. The muscle originates on the calcaneus and plantar fascia and inserts on the sides of the middle phalanges, with innervation from the medial plantar nerve.

The action of the Flexor digitorum brevis is to bend the proximal joints of the toes. It pulls on the middle phalanges to flex the proximal interphalangeal joints (toe PIPs) and also helps curl the toes by flexing the metatarsophalangeal joints (MTPs). That makes the description of plantarflexion at the PIP and MTP joints the best match for its effect. It does not flex the distal interphalangeal joints (that’s the flexor digitorum longus), nor does it cause toe abduction or MTP dorsiflexion. The muscle originates on the calcaneus and plantar fascia and inserts on the sides of the middle phalanges, with innervation from the medial plantar nerve.