Lumbar Radiculopathy Confounded: Total Knee Arthroplasty Diminishes the Patellar Tendon Reflex

STUDY DESIGN.Patellar tendon reflexes were elicited among patients who had had a unilateral total knee replacement, those planned for unilateral total knee replacement, and a cohort of controlled patients. Patellar tendon reflex (PTR) response was measured with surface electromyography. OBJECTIVE.The aim of this study was to determine if total knee arthroplasty significantly alters the PTR. SUMMARY OF BACKGROUND DATA.As part of the clinical evaluation of the spine, extremity reflexes are provoked. Reflex variation between right and left extremities can be a pathological finding in disease of the spine. It has been noted that in patients who have undergone total knee arthroplasty (TKA), the PTR is diminished on the operative side compared with the contralateral nonoperative side. PTR is part of the clinical exam when evaluating a patient for lumbar radiculopathy. METHODS.The right and left patellar tendon reflex intensities were measured by quadriceps surface electromyography in 3 groups of patients. Group 1 consisted of 21 patients with unilateral TKA who were at least 6 months postoperative. Group 2 consisted of 18 patients with unilateral severe knee arthritis indicated for TKA. Group 3, serving as the control group, included 20 patients with no evidence of knee arthritis in either knee. The average reflex response for each group was recorded and comparisons were then made between each group. RESULTS.Patients who have undergone unilateral TKA have a PTR on average of 55.1% of their contralateral uninvolved side. This is statistically significant when compared with reflexes in patients who are planned for unilateral total knee arthroplasty, 96.03% (P = 0.001) and when compared with patients without evidence for knee arthritis, 102.2% (P