Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight‐bearing flexion

Abstract

Strengthening of the hamstrings is often recommended following injury and reconstruction of the anterior cruciate ligament. It has been suggested that hamstrings activity stabilizes the knee and reduces anterior cruciate ligament load during weight-bearing flexion; however, the effects of hamstrings cocontraction on the kinematics and mechanics of the normal knee have not been assessed at physiological load levels. The aim of this study was to determine whether the addition of hamstrings force affects knee rotations, translations, and joint and quadriceps force during flexion with loads at physiological levels applied to the muscles and joints. Eight cadaveric knee specimens were tested with a servohydraulic mechanism capable of applying controlled dynamic loads to simulate quadriceps and hamstrings muscle forces throughout a physiological range of motion. A constant vertical load of physiologic magnitude was applied to the hip, and quadriceps force was varied to maintain equilibrium throughout flexion. Two conditions were tested: no hamstrings force and a constant hamstrings force equivalent to the vertical load. Hamstrings force significantly reduced internal rotation (p<0.0001) and anterior translation (p<0.0001), increased quadriceps force (p<0.0001) and normal resultant force on the tibia (p<0.0001), and reversed the direction of the shear force on the tibia (p<0.0001). These results suggest that hamstrings strengthening following anterior cruciate ligament injury may benefit anterior cruciate ligament-deficient and reconstructed knees by reducing the load in the ligament; however, they also imply that this comes at the expense of efficiency and higher patellofemoral and joint forces.

Joint stabilisers or moment actuators: The role of knee joint muscles while weight-bearing

“…sartorius and gracilis) (Buchanan and Lloyd, 1997) only contribute 5.5% to an opposing varus moment (Lloyd and Buchanan, 2001). In addition, hamstring-quadriceps cocontraction only influences anterior tibial shear forces and internal rotation during weightbearing (MacWilliams et al, 1999). Therefore, BF is classified as a specific joint stabiliser that opposes hip extension, and more importantly, valgus loads.…”

Implications of using hierarchical and six degree-of-freedom models for normal gait analyses

“…We believe this may be because Walker et al [22] did not load their specimens in a manner consistent with actual gait. When the knee is loaded, these coupled motions have been shown to disappear [23].…”

A cadaver knee simulator to evaluate the biomechanics of rectus femoris transfer

“…Previous cadaver-based knee simulator studies that did not apply hip flexor and ankle plantarflexor torques when modeling stance [15,[29][30][31][32] may have reported greater than physiologically reasonable knee extensor force magnitudes. Torques applied to the hinge knee when modeling stance phase of gait were derived from test subjects in two-legged squat.…”

“…Using a cadaver model of stance, MacWilliams et al reported that the addition of hamstrings cocontraction load equal to 30% of body weight load required a 100% increase in knee extension force in stance [29]. Applying hamstrings cocontraction in the hinge knee model resulted in an increase of knee extensor force at all knee flexion angles, albeit not as large as that reported by MacWilliams et al The combined effect of hip and ankle torques along with hamstrings cocontraction resulted in an overall decrease in knee extensor force, and a change from an almost linear relationship with KFA to a curvilinear relationship depicted in Fig.…”