Health Care

by: John Platero
National Council of Certified Personal Trainers

I’m currently contemplating replacing my ACL within 6 weeks, so here are some interesting facts I’ve learned.


· Researchers have shown the knee cruciate ligaments are loaded in the opposite manner from each other during movement and are loaded differently when in WB (Weight-bearing) and NWB (Non-Weight Bearing).

Anterior cruciate ligament strain is greater than posterior ligament (PCL) during NWB knee extension, whereas PCL strain is greater that ACL strain during WB knee extension.



· Joint surface gliding may be exaggerated in knees with injured ACL’s during WB and NWB. Therefore, PICR (path of instantaneous centers of rotation) may differ between WB and NWB.



· Evidence shows the hamstring muscles contribute to knee joint stability. In the absence of the structural integrity of the ACL, hamstring muscle co-contraction is thought to provide stability during knee extension either by virtue of its posteriorly directed force, its contribution to increase joint compression, or a combination of both mechanisms. An increase in hamstring muscle activity may be sufficient to counteract the increased gliding that might otherwise be present.



· Several studies indicate that people with an injured ACL or reconstructed ACL demonstrate greater hamstring muscle EMG activity or altered hamstring muscle timing during functional activities than do subjects without knee pathology.



· The MCL (Medial Collateral Ligament), LCL (Lateral Collateral Ligament) and meniscus are secondary anterior stabilizers of the knee joint and provide stabilization in the absence of an intact ACL. Combined, these structures contribute only up to 14% of the total resistance to the anterior tibial displacement.