Question:medium
Pain in back of leg and thigh after lifting heavy weight. Which segment involved?
Pain in back of leg and thigh after lifting heavy weight. Which segment involved?
Show Hint
Sciatica after lifting = posterolateral disc prolapse; the most commonly trapped root at L4–L5 is the traversing root.
Updated On: Jun 22, 2026
- L4
- L5
- L3
- S1
Show Solution
The Correct Option is B
Solution and Explanation
Approach this by working through the mechanism first.
Mechanism: Lifting a heavy weight with a flexed spine raises intradiscal pressure dramatically. This forces the nucleus pulposus posterolaterally through a weakened annulus - an acute lumbar disc prolapse. The herniated material presses on a nerve root, producing radicular leg pain (sciatica).
Which level? Two segments bear the greatest mechanical load and herniate most often: L4-L5 and L5-S1. A posterolateral L4-L5 disc prolapse spares the exiting L4 root and instead compresses the traversing L5 root.
Localising by symptoms: The L5 root carries sensation from the posterolateral leg, dorsum of foot and big toe. So pain referred down the back of the thigh and along the leg, triggered by heavy lifting, points to the L5 segment.
Ruling out the rest: L4 $\rightarrow$ anteromedial leg, lost knee jerk. L3 $\rightarrow$ anterior thigh, rare in lifting injury. S1 $\rightarrow$ posterior calf to sole, lost ankle jerk - the next-best but not the textbook choice for this stem.
Conclusion: The involved segment is L5 (option B).
Mechanism: Lifting a heavy weight with a flexed spine raises intradiscal pressure dramatically. This forces the nucleus pulposus posterolaterally through a weakened annulus - an acute lumbar disc prolapse. The herniated material presses on a nerve root, producing radicular leg pain (sciatica).
Which level? Two segments bear the greatest mechanical load and herniate most often: L4-L5 and L5-S1. A posterolateral L4-L5 disc prolapse spares the exiting L4 root and instead compresses the traversing L5 root.
Localising by symptoms: The L5 root carries sensation from the posterolateral leg, dorsum of foot and big toe. So pain referred down the back of the thigh and along the leg, triggered by heavy lifting, points to the L5 segment.
Ruling out the rest: L4 $\rightarrow$ anteromedial leg, lost knee jerk. L3 $\rightarrow$ anterior thigh, rare in lifting injury. S1 $\rightarrow$ posterior calf to sole, lost ankle jerk - the next-best but not the textbook choice for this stem.
Conclusion: The involved segment is L5 (option B).
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