Component rotation and anterior knee pain after total knee arthroplasty

All patients undergoing cruciate-retaining primary total knee arthroplasty for degenerative osteoarthritis at one center were studied prospectively. C linical and radiographic followup was obtained at a minimum 5 years in 102 knees in 73 patients. Patients were asked specifically about the presence o f the pain in the anterior aspect of the knee in the vicinity of the patell a and rated the severity of the pain on a visual analog scale. Significant anterior knee pain rating at least 3 of 10 on the visual analog scale was p resent in 16 knees (13 patients). Eleven patients with 14 symptomatic knees agreed to undergo computed tomography scanning to accurately determine the rotation of the tibial and femoral components. The epicondylar axis and ti bial tubercle were used as references using a previously validated techniqu e. A control group of 11 asymptomatic patients (14 knees), matched for age, gender, and length of followup also underwent computed tomography scanning . All patients in both groups had normal axial alignment. There was a highl y significant difference in tibial component rotation between the two group s with the patients with anterior knee pain averaging 6.2 degrees internal rotation compared with 0.4 degrees external rotation in the control group. There also was a significant difference in combined component rotation with the patients with anterior knee pain averaging 4.7 degrees internal rotati on compared with 2.6 degrees external rotation in the control group. There was no significant difference in the degree of radiographic patellar tilt o r patellar subluxation between the two groups. Patients with combined compo nent internal rotation were more than five times as likely to experience an terior knee pain after total knee arthroplasty compared with those with com bined component external rotation. Component malrotation is a significant f actor in the development of anterior knee pain after total knee arthroplast y.