If someone had asked me to define â??L3â? several months ago, I would have guessed it somehow involved the Los Angeles rock band that called itself L7. I have since learned through experience that a misaligned L3 vertebra can cause strong pain in the lower back. The pain can be so strong that it spreads to a leg. That was the story of my life throughout the summer and until recently. I have not known such exhausting pain since rupturing my spleen during my childhood.