Knee Kinematic Profiles during Drop Landings: A Biplane Fluoroscopy Study

TORRY, M. R., K. B. SHELBURNE, D. S. PETERSON, J. E. GIPHART, J. P. KRONG, C. MYERS, J. R. STEADMAN, and S.L.-Y. WOO. Knee Kinematic Profiles during Drop Landings: A Biplane Fluoroscopy Study. Med. Sci. Sports Exerc., Vol. 43, No. 3, pp. 533-541, 2011. Introduction: The six degrees of freedom knee motion during dynamic activities is not well understood. Purpose: Biplane fluoroscopy was used to measure the three-dimensional rotations and translations of healthy knees during stiff drop landings and to determine the relationships between three-dimensional rotations and anterior (ATT) and lateral tibial translations (LTT). Methods: Six males performed stiff drop landings from 40 cm while being filmed using a high-speed, biplane fluoroscopy system. Initial, peak, and excursions for rotations and translations were calculated, and relationships and changes in these variables were assessed (alpha = 0.05). Results: Knee flexion at contact was 13.9 degrees +/- 9.2 degrees (mean +/- SD) and increased to a peak of 44.0 degrees +/- 17.2 degrees with an excursion of 31.5 degrees +/- 14.1 degrees. Knee varus/valgus angle at contact was -0.3 degrees +/- 1.8 degrees varus; subjects progressed into a mean peak valgus position of 1.5 degrees +/- 0.9 degrees with total excursion of 2.5 degrees +/- 0.9 degrees. Four of six subjects landed externally rotated (2.5 degrees +/- 3.0 degrees); two landed internally rotated (-4.9 degrees +/- 1.5 degrees), yielding a contact angle of -2.4 degrees +/- 3.0 degrees of internal rotation, a peak internal rotation of -5.5 degrees +/- 6.0 degrees, and excursion of 3.1 degrees +/- 5.5 degrees. Peak ATT were 4.3 +/- 0.7 mm (excursion = 2.1 +/- 0.9 mm), occurring within 50 ms after contact. Peak LTT were 1.5 +/- 1.4 mm (excursion = 2.6 +/- 1.6 mm). Significant regressions were found between ATT and knee valgus angle (r(2) = 0.39, P = 0.006), between LTT and internal rotation (r(2) = 0.96, P < 0.0001), and between LTT and knee valgus angle (quadratic, r(2) = 0.90, P < 0.0001). Conclusion: This study provides a direct correlation between knee valgus angle with knee ATT and LTT during drop landings.