Outline of focal neuropathies in the lower limb
| Nerve | Site of lesion | Common causes | Motor deficit | Sensory deficit | Differential diagnosis |
|---|---|---|---|---|---|
| Common | |||||
| Lateral cutaneous nerve of the thigh | Inguinal ligament | Obesity, pregnancy, surgery | None | Lateral thigh | L2 radiculopathy |
| Common peroneal | Fibular head | External compression (leg crossing, iatrogenic), trauma | Foot dorsiflexion and eversion, toe extension | Lateral calf and dorsum of foot | L5 radiculopathies, proximal sciatic lesions. Also upper motor neurone weakness and motor neurone disease |
| Interdigital | Between heads of metatarsals | Entrapment | None | Web spaces between affected toes | |
| Uncommon | |||||
| Femoral | Psoas haematoma, iatrogenic injury, trauma | Hip flexion, knee extension | Anterior thigh, medial calf | L3, L4 radiculopathies, diabetic amyotrophy | |
| Sciatic | Pelvis, buttock or thigh | Trauma, compression in buttock, tumour, injection | Hamstrings plus common peroneal and tibial nerve deficits | Posterior cutaneous nerve of thigh plus common peroneal plus posterior tibial | L5, S1 radiculopathies |
| Tibial, at ankle | Tarsal tunnel | Entrapment | Abductor hallucis (not reliably tested clinically) | Distal sole, sparing heel | Partial sciatic, S1 radiculopathy |
| Perineal | Alcock’s canal | Cycling | None | Penis or labia majora | Conus lesions |
| Saphenous | Thigh or knee | Knee surgery or arthroscopy | None | Medial calf | |
| Rare | |||||
| Tibial, at knee | Trauma | Plantar flexion, inversion | Sole of foot, including heel | Partial sciatic, S1 radiculopathy | |
| Posterior cutaneous nerve of the thigh | Compression, trauma | None | Posterior thigh | S3, S4 radiculopathy | |
| Obturator | Obturator foramen | Obturator hernia, pelvic tumours, surgery | Adductors of the hip | Medial thigh | Lumbosacral plexopathy |
| Gluteal | Trauma | Hip extensors, abductors | None | ||
| Sural | Trauma, surgery (especially biopsy!) | None | Lateral aspect of foot | ||