REIDER PART 2
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Chapter 9_Lumbar Spine 353

Patellar Tendon Reflex (L4). The patellar tendon reflex is usually assessed with the patient seated on the side of the examination table with the knees flexed and the feet dangling. The examiner then sharply strikes the midportion of the patellar tendon with the fiat side of a rubber rcflex hammer. The examiner*s other hand may rest lightly on the patients ąuadriceps to feel for a muscle contraction (Fig. 9-22A).

In most patients, a contraction of the muscle is felt in response to the strike of the hammer, and in some patients the knee is seen to extend slightly. If no reflex is observed, the examiner may try to reinforce the reflex. To do this, the patient is instructed to hook the fingers of both hands together and puli against each other isomet-rically. While the patient is pulling, the examiner again strikes the patellar tendon (Fig. 9-22B). This techniquc may produce a patellar tendon reflex in patients in whom the reaction is otherwise unobtainable.

The patellar tendon reflex is morę difficult to elicit than the Achilles tendon reflex. In some normal patients, the patellar tendon reflex is symmetrically absent. As in many other aspeets of the physical examination, lack of symmetry is the key to evaluating this test. The patellar tendon reflex is primarily used to evaluate the L4 nerve root. Some contribution from L3 is also present.

Tibialis Posterior Reflex (L5). The available reflexes for the L5 nerve root are difficult to elicit. They inelude the tibialis posterior reflex and the medial hamstring rcflex. The tibialis posterior reflex is evaluated in the seated patient. The examiner holds the patient s foot in a smali amount of eversion and dorsiflexion and strikes the posterior tibial tendon just below the medial malleolus. The