L4 anterior ramus
Roots · L4
The 'furcal' (forked) nerve: most of it stays in the lumbar plexus (femoral, obturator), while a smaller descending branch joins L5 to form the lumbosacral trunk, so L4 fibres reach both plexuses.
Detail
- Dermatome
- Medial leg and medial malleolus
- Myotome
- Ankle dorsiflexion (tibialis anterior), knee extension
- Reflex
- Knee jerk (L3–L4)
When it goes wrong
L3/4 disc prolapse or foraminal stenosis compressing the L4 root
Weak knee extension and ankle dorsiflexion, reduced knee jerk, pain and numbness down the medial leg to the medial malleolus
Practise this structure
1 question in the bank tagged Reflexes.