Downhill walking: A stressful task for the anterior cruciate ligament?

Abstract

Accelerated rehabilitation after anterior cruciate ligament (ACL) reconstruction has become increasingly popular. Methods employed include immediate extension of the knee and immediate full weight bearing despite the risks presented by a graft pull-out fixation strength of 200-500 N. The purpose of this study was to calculate the tibiofemoral shear forces and the dynamic stabilising factors at the knee joint for the reasonably demanding task of downhill walking, in order to determine whether or not this task presented a postoperative risk to the patient. Kinematic and kinetic data were collected on six male and six female healthy subjects during downhill walking on a ramp with a 19% gradient. Planar net joint moments and mechanical power at the knee joint were calculated for the sagittal view using a force platform and videographic records together with standard inverse dynamics procedures. A two-dimensional knee joint model was then utilised to calculate the tibiofemoral shear and compressive forces, based on the predictions of joint reaction force and net moment at the knee. Linear envelopes of the electromyographic (EMG) activity recorded from the rectus femoris, gastrocnemius and biceps femoris muscles were also obtained. The maximum tibiofemoral shear force occurred at 20% of stance phase and was, on average, 1.2 times body weight (BW) for male subjects and 1.7 times BW for female subjects. The tibiofemoral compressive force was 7 times BW for males and 8.5 times BW for females during downhill walking. The hamstring muscle showed almost continuous activity throughout the whole of the stance phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Can Joint Contact Dynamics Be Restored by Anterior Cruciate Ligament Reconstruction?

“…2). We selected downhill running for the testing activity because it generates greater shear stress on the knee [25] and has been used previously to identify abnormal knee kinematics after conventional SB reconstruction [32,33]. We collected three trials for each limb of each patient.…”

Joint Load Considerations in Total Knee Replacement

“…Electromyographic activity, recorded from our subjects during their downhill walking, clearly indicated the presence of hamstring, gastrocnemius and quadriceps muscle co-activity during the stance phase. 19 The measures of joint compression reported here are therefore conservative estimates but still exceed eight times bodyweight for downhill walking. Force values equivalent to three to four times BW have previously been used in most biomechanical tests evaluating total knee replacements.…”

(i) Biomechanics of the knee joint

“…A seminal study in the late 1960s estimated TF joint forces of 3.4 body weight (BW) when walking, 4.3 BW when ascending stairs and 4.0 BW when descending a ramp, 4,5 whilst a later study calculated up to 8.5 BW TF joint forces when walking downhill. 6 In the PF joint, when the knee is near extension, the lines of action of the patellar tendon (PT) and quadriceps muscle (Q) are almost co-linear in the sagittal plane, resulting in a small joint force (Figure 4a). However, as the knee flexes, the angle between the lines of action of the PT and Q reduces, resulting in an ever increasing PF joint force up to approximately 70 knee flexion, where the PT tension is approximately 70% that of Q ( Figure 4b).…”