Category: Blogs
Share

Cannon J, Cambridge EDJ, McGill SM. Anterior Cruciate Ligament Injury Mechanisms and the Kinetic Linkage: The Effect of Proximal Control During Bilateral Landings. J Orthop Sports Phys Ther, 2019 49: 601-610.

The above article will be the subject of two blogs and two accompanying videos in the Gray Institute® series called “Evidence that Matters for Function.” In spite of some limitations, which the authors acknowledge, this study has a lot to offer practitioners of any movement discipline / profession. First, their rationale for the study design covers a lot of valuable information in a logical manner (63 references). The scientific rationale for the study validates the Chain Reaction® approach advocated by Dr. Gary Gray for more than 40 years. Second, the results of the study support the Applied Functional Science® (AFS) of addressing links in the kinematic chain other than where the injuries / symptoms are located.

The initial study group consisted of 18 university-aged women. The subjects performed Drop Vertical Jumps (DVJ) from a height of 31 centimeters, onto 2 adjacent force plates. The landing was transformed into a maximum vertical jump without any pause. In addition to force plate data, motion analysis of the joints and electromyography (EMG) of 24 muscles was recorded and analyzed. The mean of three jumps was averaged, and subjects were categorized as having bilateral, unilateral, or no valgus. Initial analysis found 4 subjects with bilateral valgus, 10 subjects with unilateral valgus and 4 had no valgus. 

This blog will focus on the findings to the lumbar spine motion, spine muscle activation, and the calculated rotational stiffness at the lumbar spine. The spinal muscles for which EMG was collected were the rectus abdominus internal and external obliques, the erector spinae in both the thoracic and lumbar regions, and the latissimus dorsi. The article only reported the spine motion in the sagittal plane. The amount of spine flexion during landing was much larger in the bilateral valgus group (38 degrees) compared to the unilateral valgus (26 degrees) and the no valgus group (24 degrees). Using the EMG data and a model to calculate Joint Rotational Stiffness (JRS), the results indicate that the greater the JRS in the sagittal plane, the lower the degree of knee valgus. This supports the concept of “proximal control” of knee motion.

One benefit of the small number of subjects in this study is that the authors plotted data of each subject. Generally, the plots of spine flexion and JRS against medial knee displacement (valgus) support the average data cited above. However, the individual data demonstrates one of the disadvantages of averaging. There were 3 subjects in the unilateral valgus group that demonstrated a smaller lumbar spine flexion angle than any of the subjects in the no valgus group. There was a subject in the bilateral valgus group that had the same amount of spine flexion as a subject with no valgus, and less than 4 subjects in the unilateral group. 

One principle of the AFS approach is that, in spite of general tendencies, each patient / client is an individual that must be assessed and treated as such. The individual data supports this approach. In fact, the simple linear regression performed on the lumbar spine flexion angle and JRS, showed these variables explained very little of the differences in the degree of medial knee displacement for the subjects in this study. This doesn’t mean that trunk control does not play a critical role during DVJ. What the results of this study suggest is that many factors, including hip muscle strength and foot motion, contribute to control of movement; necessitating the ability to assess and train using global movements where all the joints and muscles are integrated into a single movement system.

The Chain Reaction® seminars, taught by Dr. Gary Gray, have been advocating this integrated approach for more than 30 years. Gary would agree that core strength is a critical part of the proximal control that can reduce the chance of knee injury. But he would assert that the simultaneous motion and control of motion (mobile-stability) must be assessed using strategies that leverage global movements consisting of motion at all the joints in all three planes.

Previous
Evidence that Matters for Function: Proximal Control of Dynamic Knee Valgus – VLOG
Next
Evidence that Matters for Function: Proximal Control of Dynamic Knee Valgus (Part 2) – VLOG

Leave a Reply

Your email address will not be published. Required fields are marked *

Be the first to get Gray blogs and podcasts!