In vivo elongation of the anterior cruciate ligament and posterior cruciate ligament during knee flexion.
BACKGROUND
Most knowledge regarding cruciate ligament function is based on in vitro experiments.


OBJECTIVE
To investigate the in vivo elongation of the functional bundles of the anterior cruciate ligament and posterior cruciate ligament during weightbearing flexion.


OBJECTIVE
The biomechanical role of functional bundles of the anterior cruciate ligament and posterior cruciate ligament under in vivo loading is different from that measured in cadavers.


METHODS
In vivo biomechanical study.


METHODS
Elongation of the anterior cruciate ligament and posterior cruciate ligament was measured during a quasi-static lunge using imaging and 3-dimensional computer-modeling techniques.


RESULTS
The anterior-medial bundle of the anterior cruciate ligament had a relatively constant length from full extension to 90 degrees of flexion. The posterior-lateral bundle of the anterior cruciate ligament decreased in length with flexion. Both bundles of the posterior cruciate ligament had increased lengths with flexion.


CONCLUSIONS
The data did not demonstrate the reciprocal function of the 2 bundles of the anterior cruciate ligament or the posterior cruciate ligament with flexion observed in previous studies. Instead, the data suggest that there is a reciprocal function between the anterior cruciate ligament and posterior cruciate ligament with flexion. The anterior cruciate ligament plays a more important role in low-flexion angles, whereas the posterior cruciate ligament plays a more important role in high flexion.


CONCLUSIONS
Understanding the biomechanical role of the knee ligaments in vivo is essential to reproduce the structural behavior of the ligament after injury (especially for 2-bundle reconstructions) and thus improve surgical outcomes.
Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. gli1@partners.org
Guoan
G
Li
Louis E
LE
DeFrate
Hao
H
Sun
Thomas J
TJ
Gill
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology* / Q000502:physiology*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006801:Humans; D007718:Knee Injuries / Q000534:rehabilitation; D007719:Knee Joint / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D009068:Movement; D016119:Posterior Cruciate Ligament / Q000033:anatomy & histology* / Q000502:physiology*; D016474:Weight-Bearing