Which of the following structures is evaluated for knee reflex?

The structure evaluated for the knee reflex is the patella. This reflex, also known as the patellar reflex or knee-jerk reflex, is a common neurological test used to assess the integrity of the spinal cord at the level of L2 to L4. When the patellar tendon, which is located just below the patella, is tapped with a reflex hammer, it sends a signal through the sensory neurons to the spinal cord, which then triggers a response causing the quadriceps muscle to contract. This contraction results in the characteristic leg extension at the knee.

While the Achilles tendon, biceps tendon, and triceps tendon are also important in assessing reflexes, they correspond to different reflex arcs and not the knee reflex specifically. The Achilles reflex evaluates the S1-S2 spinal segments, the biceps reflex assesses C5-C6, and the triceps reflex focuses on C7-C8. Therefore, the patella is the correct structure associated with the knee reflex assessment.