L4 radiculopathy typically presents with weakness in which muscle?

L4 radiculopathy typically presents with weakness in which muscle?

• A. Anterior tibialis
• B. Gastrocnemius
• C. Peroneus longus
• D. Quadriceps

Answer: (A)

L4 radiculopathy is most clearly reflected by weakness of ankle dorsiflexion, driven by the tibialis anterior. When the L4 nerve root is affected, the tibialis anterior loses its normal signal, making the foot hard to lift upward at the front—this dorsiflexion weakness is a hallmark sign of L4 involvement. Clinically, you may also see a diminished patellar reflex and sensory changes along the medial leg, which further support L4 involvement. Weakness of the gastrocnemius points to the S1/S2 region (plantar flexion), not L4. Quadriceps weakness can occur with L3-L4 involvement, but it’s less specific to L4 alone since L3 can contribute as well. Peroneus longus weakness involves different myotomes and is less characteristic of L4 radiculopathy.

L4 radiculopathy is most clearly reflected by weakness of ankle dorsiflexion, driven by the tibialis anterior. When the L4 nerve root is affected, the tibialis anterior loses its normal signal, making the foot hard to lift upward at the front—this dorsiflexion weakness is a hallmark sign of L4 involvement. Clinically, you may also see a diminished patellar reflex and sensory changes along the medial leg, which further support L4 involvement.

Weakness of the gastrocnemius points to the S1/S2 region (plantar flexion), not L4. Quadriceps weakness can occur with L3-L4 involvement, but it’s less specific to L4 alone since L3 can contribute as well. Peroneus longus weakness involves different myotomes and is less characteristic of L4 radiculopathy.