Posterior Displacement of the Tibia Increases in Deep Flexion of the Knee
- 236 Downloads
Deep knee flexion is important to proper function for some activities and in some cultures, although there are large posterior forces during high knee flexion. Most of what we know about posterior restraint and stability, however, has not been determined from deep flexion and without distinguishing motion in the medial and lateral compartments.
We therefore evaluated (1) the difference in posterior displacement between the medial and lateral compartments at a commonly used flexion angle of 90°; (2) that of deeply flexed knees at 135°; and (3) the difference in kinematics in the medial and lateral compartments. We analyzed posterior stability in 21 normal knees using interventional open magnetic resonance imaging (MRI) system.
When manual posterior stress was applied, the posterior displacements of the tibia were 0.6 mm/2.1 mm (medial/lateral) at 90° and 0.6 mm/3.6 mm at 135°. The posterior aspect of the femoral medial condyle moved 7.5 mm anteriorly with knee flexion, whereas the lateral condyle moved 1.3 mm anteriorly. The contact point of the lateral compartment moved 9.2 mm posteriorly with knee flexion, whereas the contact point of the medial compartment moved 2.3 mm anteriorly.
Posterior displacement was larger in the lateral compartment at both flexion angles with manual posterior stress. As the knees flexed from 90° to 135°, posterior displacement became larger in the lateral compartment.
Cruciate-retaining total knee arthroplasty (TKA) or posterior cruciate ligament (PCL) reconstruction surgery should aim to achieve stability on the medial side and a few millimeters of laxity at the lateral side at 90° flexion with increasing laxity only on the lateral side in deep flexion.
We thank Sumako Nishimura and Takefumi Yasunaga (Hitachi Medical Corporation) for assistance in operating the MRI system. We are grateful to Dr. Junji Kishimoto (Digital Medicine Initiative, Kyushu University) for advice on the statistical analysis. We also thank Dr. Hiromasa Miura, Dr. Ken Okazaki, and Dr. Taka-aki Moro-oka (Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University) for assistance with this study.
- 2.Brantigan OC, Voshell AF. The mechanics of the ligaments and menisci of the knee joint. J Bone Joint Surg. 1941;23:44–66.Google Scholar
- 4.Chmell MJ, Scott RD. Balancing the posterior cruciate ligament during posterior cruciate retaining total knee arthroplasty: description of the POLO test. J Orthop Tech. 1996;4:12–15.Google Scholar
- 20.Okazaki K, Miura H, Matsuda S, Yasunaga T, Nakashima H, Konishi K, Iwamoto Y, Hashizume M. Assessment of anterolateral rotatory instability in the anterior cruciate ligament-deficient knee using an open magnetic resonance imaging system. Am J Sports Med. 2007;35:1091–1097.CrossRefPubMedGoogle Scholar
- 25.Scott WN (ed). Insall & Scott Surgery of the Knee. Ed 4. Philadelphia, PA: Churchill Livingstone; 2005.Google Scholar
- 26.Shultz SJ, Shimokochi Y, Nguyen AD, Schmitz RJ, Beynnon BD, Perrin DH. Measurement of varus-valgus and internal-external rotational knee laxities in vivo—Part II: relationship with anterior-posterior and general joint laxity in males and females. J Orthop Res. 2007;25:989–996.CrossRefPubMedGoogle Scholar