Asymmetry of mediolateral laxity of the normal knee.
BACKGROUND
Understanding the normal kinematics of the joints is important for reconstructive surgery. However, only a few extensive studies have been done on medial and lateral laxity of the normal knee.


METHODS
Radiographs of 50 normal knees were obtained under varus and valgus stress in both extension and flexion and the relative angle of the articular surface was measured.


RESULTS
In extension, the mean angle was 4.9 degrees in varus stress and 2.4 degrees in valgus stress. In flexion, the mean angle was 4.8 degrees in varus stress and 1.7 degrees in valgus stress. Lateral laxity was significantly greater than medial laxity in both extension and flexion.


CONCLUSIONS
Lateral laxity may be necessary for the medial pivot movement of the normal knee. There is some disagreement regarding the importance of pursuing the perfect rectangular gaps during total knee arthroplasty (TKA). The methods for measuring the tension of soft tissues during the operation are not accurate and do not always reflect the postoperative tensions of dynamic phases, such as walking and standing. Slight lateral laxity can be accepted with TKA, and further studies are necessary to determine whether prosthesis lift-off occurs in the replaced knee with slight lateral laxity similar to that in the normal knee.
Okazaki
Ken
K
Department of Innovative Medical Technology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Miura
Hiromasa
H
Matsuda
Shuichi
S
Takeuchi
Naohide
N
Mawatari
Taro
T
Hashizume
Makoto
M
Iwamoto
Yukihide
Y
D000328:Adult; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D013314:Stress, Mechanical