Muscles: Actions, Origins & Insertions Practice Test

This question tests how origin and insertion determine a muscle’s action. A muscle that starts on the lateral tibial condyle and the anterior surface of the fibula (with the interosseous membrane) and then splits to insert into the extensor expansions of toes 2–5 is the extensor digitorum longus. Its job is to extend the toes (2–5) at the toe joints, and it also helps dorsiflex the foot.

The other options don’t fit the insertion pattern: fibularis longus attaches to the plantar side of the foot (base of the 1st metatarsal and medial cuneiform), tibialis anterior inserts on the medial cuneiform and 1st metatarsal, and the vastus medialis inserts into the patellar ligament/tibia for knee extension, not the toes.