<prompt> A patient while lifting a heavy weight presents with sudden onset pain in the lower back radiating along the postero-lateral thigh and lateral leg to the big toe with numbness. The most likely diagnosis is:L5 fractureL3 - IA Disc prolapsedL4 - L5 Disc prolapsedL5 - SI Disc prolapse  <response>: C i.e. L4 -- L5 Disc prolapsed Sudden onset lower back pain with radioculopathy while lifting something heavy from ground i.e. in spinal flexion indicates acute PIVD prolapsed of interveebral disc. Pain or paresthesia along posterolateral aspect of lower thigh, anterolateral aspect of knee and leg and dorsal surface of foot covering great toe, 1st web space upto 3rd MTP joint but never little toe indicates compression of L5 nerve root i.e. prolapsed of L4 --L5 disc. Level of Disc Prolapse Compressed Nerve Root Pain and Sensory Loss Motor Weakness Reflex Affected L3-L4 L4 - Over medial malleous - Ankle dorsiflexion TA at Knee quadricepspatella ASIA - Medial aspect both anterior ASIA - Knee extension Quadriceps; jerk posterior of lower thigh, knee, leg calf and ankle L4 is main root - Hipthigh adduction L4-L5 L5 - Dorsal of foot at 3rd MTP - Great toe extensor EHL; at Knee Ankle jerks are joint ASIA ASIAQ normal; or knee - Posterolateral buttock - - Foot eversion peroneii; paradoxically increased due thigh esp lower, lateral aspect anterior posterior of knee and leg calf and dorsum of foot covering great toe, 1st web space 3rd main root - Anklefoot dorsiflexion TA - Toe dorsiflexors - Hip abduction gluteus medius to weak knee flexion MTP joint but never little toe. - Knee flexion L5-S1 S1 - Lateral aspect of calcaneus ASIA - Lateral aspect of ankle foot both on dorsal plantar aspect involving lateral malleolus, lateral border of foot little toe - Ankle foot plantar flexion gastrocnemius soleus; main root; ASIA - Abductor hallucis great toe flexion; main root - Hip extension gluteus maximus Ankle jerk 