The clinical efficacy of the a-angle in measuring patellar alignment.

Patellar malalignment syndrome is a condition that presents with clinical symptoms such as popping, giving-way, effusion, buckling, weakness, patellar subluxation, and pain with certain activities. Realignment of the patella through conservative techniques has become the main emphasis of treatment. Due to this emphasis on patellar realignment, a need for a quantitative measurement of patellar orientation has developed. The A-angle is a goniometric measurement that assesses the relationship of the patella to the tibial tubercle. The purpose of this study was to examine the reliability of this measurement and to assess if the A-angle differed between control and symptomatic groups. Thirty subjects participated in Part 1 (28 females, 2 males) and in Part 2 (24 females, 6 males) of the study. The A-angle was measured with a blinded goniometer. Intratester and intertester reliability were assessed with measurements taken 5 minutes apart. Correlations of repeated measures (Pearson product) for intratester reliability were .87. Correlations of repeated measures (Pearson product) for intertester reliability were .59. A t-test showed that the groups significantly differed at p>.001. The results of this investigation demonstrate that the goniometric A-angle measurement is reliable when taken by the same examiner. There was a significant difference in the A-angle between the patellofemoral and control groups. J Orthop Sports Phys Ther 1992;16(3):136-139.