Pediatrics Rehabilitation Exam 2 Practice

The ability to crawl, come to stand, and walk with deviations hinges on preserved strength for knee extension, which lets the leg straighten to support the body during standing and the early steps of walking. The knee extensor group is mainly supplied by the L3–L4 myotomes (quadriceps). With L3–L4 intact, a child can use hip flexors (L2–L3) to initiate movement for crawling and, importantly, can straighten the knee to stand and take first steps, albeit with gait deviations due to weaker distal control. If the level were higher (L2–L3), knee extension would be insufficient, making coming to stand and walking much more difficult. If the level were lower (L4–L5 or S1–S2), distal ankle control would be relatively better or different, which changes the pattern of gait and can reduce the likelihood of this exact trio of milestones being achieved together. Hence, L3–L4 is the most consistent motor level supporting crawling, coming to stand, and walking with deviations.