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Lower limb nerve injuries
Where each nerve is injured, what is lost, and the sign that gives it away.
| Nerve (roots) | Typical injury | Motor loss | Sensory loss | Classic sign |
|---|---|---|---|---|
| Femoral (L2–L4) | Retroperitoneal or iliopsoas hematoma (anticoagulation); hip or pelvic surgery; femoral catheterization | Quadriceps — weak knee extension | Anterior thigh; medial leg (saphenous nerve) | Knee buckles; lost patellar reflex |
| Obturator (L2–L4) | Pelvic surgery, childbirth, pelvic fracture | Hip adductors | Medial thigh | Weak adduction; leg swings outward when walking |
| Superior gluteal (L4–S1) — see gluteus medius and minimus | Misplaced intramuscular injection; hip surgery | Gluteus medius and minimus, tensor fasciae latae | None | Trendelenburg sign — the pelvis drops on the side opposite the lesion |
| Inferior gluteal (L5–S2) — see gluteus maximus | Posterior approach to the hip | Gluteus maximus | None | Difficulty rising from a chair or climbing stairs |
| Sciatic (L4–S3) | Posterior hip dislocation; misplaced gluteal injection; hip arthroplasty | Hamstrings and every muscle below the knee | Leg and foot except the medial side (saphenous) | Foot drop with weak knee flexion |
| Common fibular (L4–S2) | Fibular neck fracture; tight cast or brace; habitual leg crossing; prolonged squatting | Ankle dorsiflexors and evertors | Lateral leg and dorsum of the foot | Foot drop with steppage gait |
| Deep fibular — branch of the common fibular nerve | Anterior compartment syndrome (see compartments of the leg) | Ankle and toe dorsiflexors | First web space only | Foot drop |
| Tibial (L4–S3) | Tarsal tunnel behind the medial malleolus; posterior knee trauma | Plantarflexors, toe flexors, intrinsic foot muscles | Sole of the foot | Can't stand on the toes; burning sole (tarsal tunnel) |
| Lateral femoral cutaneous (L2–L3) | Meralgia paresthetica — tight belts, obesity, pregnancy | None (sensory nerve) | Anterolateral thigh | Burning or numb anterolateral thigh |
| Pudendal (S2–S4) | Childbirth; prolonged cycling | External urethral and anal sphincters, perineal muscles | Perineum and genitalia | Incontinence; perineal numbness |
Foot drop with weak eversion but normal inversion points to the common fibular nerve; weak inversion as well suggests an L5 radiculopathy.