At the L5 level, which muscle groups show 3/5 strength?

At the L5 level, which muscle groups show 3/5 strength?

• A. Lateral knee flexors and ankle invertors
• B. Hip abductors
• C. Hip adductors
• D. Long toe extensors

Answer: (A)

When you assess motor level at L5, a 3/5 strength means the person can move the muscle against gravity but not against resistance. At this level, the muscle groups most likely to show this degree of weakness are those innervated primarily by the L5 nerve root with limited overlap from adjacent levels: the lateral knee flexors (the hamstrings on the outer side, notably the biceps femoris portion) and the ankle invertors (tibialis posterior). These movements depend strongly on L5, so they tend to be the ones that run into noticeable weakness to the level of moving only against gravity.

In contrast, other L5-related actions, such as long toe extension, can vary in strength because of overlapping innervation from nearby levels and individual differences, so they may not consistently present as 3/5. Hip movements involve additional nerve contributions and may remain stronger or show a different pattern of weakness, making them less consistently 3/5 at the L5 level.