College of Massage Therapists of British Columbia (CMTBC) Practice Exam

A diminished patellar reflex during a lower extremity assessment may indicate lesions in which nerves?

1. L3-L4

2. L4-L5

3. L5-S1

4. S1-S2

The correct answer is: L3-L4

A diminished patellar reflex specifically points towards possible involvement of the L3-L4 nerve roots. The patellar reflex, also known as the knee-jerk reflex, is primarily mediated by the patellar tendon which connects to the quadriceps muscle. When the tendon is tapped, sensory signals travel through the femoral nerve to the spinal cord at the L3 and L4 levels, which then sends signals back through the same pathways to elicit the reflexive contraction of the quadriceps muscle. When there are lesions affecting the L3 or L4 spinal nerves, particularly where they exit from the spinal column, it can impair the normal neuronal pathways required for this reflex to occur effectively. In clinical assessments, a diminished or absent patellar reflex would therefore suggest that there may be some disruption in those specific nerve roots, making the L3-L4 level the most relevant option. Other levels such as L4-L5, L5-S1, or S1-S2 are less directly connected to the patellar reflex mechanism, focusing instead on other muscle groups or reflexes, which makes them less pertinent when considering this specific reflex.