Pozzi F, Snyder-Mackler L, Zeni J. Relationship Between Biomechanical Asymmetries During A Step Up and Over Task and Stairclimbing After Total Knee Arthroplasty. Clin Biomech 2015, 30: 78-85

The purpose of this study was to compare patient performance 6 months after total knee replacement with a matched group of healthy subjects. There were 20 subjects in each group. The subjects performed 3 well-documented functional performance tests; Timed Up and Go, Stair Climbing Test, and 6-Minute Walk Test. Biomechanical data was collected on a Step Up and Over Test. The subjects step up on a 20.5 cm step and then down the other side. Trials were performed with the operated limb stepping up and with the operated limb stepping down.

The major findings were consistent with previous studies for walking and stair climbing. Functional performance increases and pain decreases after total knee replacement. In spite of this improvement, left-right asymmetries were found between the operated patients and the control group for both the stepping up and down. The operated knee, when compared to the non-operated side and the control group, showed lower peak sagittal plane knee moments and peak power during the stepping up. During landing, the operated knee demonstrated less motion excursion and decreased power absorption.

In the Step Up and Over Test, significant compensatory patterns were identified in the ipsilateral hip and the contralateral limb. During both stepping up and landing, the hip on the operated side generated move power and absorbed more power during the respective functions. They also identified alterations in the non-operated limb compared to the control group. These compensations appear to be the result of the movement system’s adjustments to restore function in spite of deficits in strength and power in the operated knee. The authors suggest that even after knee impairments resolve, these patterns may continue.

So why does this research matter for function? First, it documents deficits in knee function 6 months after surgery. These deficits persist, even in the presence of improved function. Second, it demonstrates the Chain Reaction® nature of the movement system where other parts of the body compensate. Finally, it suggests that these compensatory patterns can persist, preventing full restoration of function at the knee.

For over 30 years, the Chain Reaction® seminars from Gray Institute® has taught how the different joints and muscles act as a task-oriented system. After injury or surgery, the systems approach to rehabilitation (and training) empowers the movement practitioner to enhance function by teaching the body to use all of its resources to substitute for the deficits. This promotes improved function faster than what might occur as the body “discovers” how to compensate.

However, this article reminds us that once function improves, it is essential to take away the compensatory substitutions. Following knee replacement, if the knee is to maximally recover, there must be a strategy of reducing the substitutions while maintaining the functional improvements. In the Chain Reaction® seminars this is referred to as “tweaking in” and “tweaking out” – “tweaking in” to accelerate functional improvement and then “tweaking out” to restore the motion, strength, and power resources at the surgical joint, which ultimately enhances function even further. Understanding the Chain Reaction® Biomechanics of the body provides appropriate strategies for a logical progression from “tweaking in” to “tweaking out.”