Category: Applied Functional Science
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Pozzi F, Snyder-Mackler L, Zenni J. Relationship between biomechanical asymmetries during a step up and over task and stair climbing after total knee arthroplasty. Clin Biomech 2015, 30: 78-85.

This study was designed to add to the existing knowledge about function following knee replacement. They investigated two (2) tasks with greater challenges to the body compared to walking on level surfaces. The tasks, stepping over an object and stairclimbing, were selected to determine the degree to which deficits and side-to-side differences existed six (6) months after surgery. Twenty (20) patients with unilateral Total Knee Arthroplasty (TKA) were compared to an age-matched control group. Comparisons between the operated and non-operated legs, as well as to the control group were performed.

Side-to-side comparisons provide a great measure of recovery, but can be influenced by existing deficits in the non-operated limb. Comparison with the control group provided information regarding functional recovery. The subjects performed functional tests on one day, and biomechanical tests on another day. The functional tests were Timed Up and Go (TUG), Stair Climbing Test (SCT), and the 6 Minute Walk (6MW). The TKS subjects covered 16% less distance during the 6MW.  The deficits for the TKA subjects compared to the control group were 33% for the TUG and 41% for the SCT. All three tests suggest that these patients were not fully recovered by 6 months, which is not surprising. But what should movement practitioners work on to enhance the recovery of these patients / clients?

The results of the biomechanical testing portion of this study, along with the results of other studies, can give us some suggestions. When the operated leg was compared to the non-operated leg, isometric quadriceps strength (tested with the knee flexed 75 degrees) was 18% higher on the non-surgical side. During the step up and over functional task, the sagittal plane knee moment and knee power were reduced compared to the intact side. The operated side hip compensated for the knee by increasing the power to step up. When the operated side was accepting the load of stepping down, the absorption was decreased, and the knee flexion excursion was reduced.

If we focus on stepping up, it is actually a great compensation that the hip power on the operated side was increased. In fact, the “tweaking in” strategy of Applied Functional Science® would create movements that would purposely create more contribution from the hip extensors to reduce the load on the knee during the initial stages of rehabilitation or training. Once the task can be completed successfully and there is close to side-to-side symmetry, then the movement practitioner must design a strategy to gradually reduce the hip contribution in order to increase the knee power. This can be accomplished performing step up exercise by reaching with the arms to either increase or decrease the contribution of the hip.

When addressing the second deficit listed above (poor absorption during landing) the same “tweaking in” to “tweaking out” progression can be utilized. In addition to strength deficits, the patient / client might also be dealing with a lack of control that allows the knee to flex under load. The TKA patients had less knee excursion when landing. Even though the knee joint probably has plenty of knee flexion, the body will not use that motion unless it knows that it can be controlled. At Gray Institute®, this is referred to as Mostability™ (Mobility and Stability). Dr. Gary Gray says. “Mobility without Stability is Instability.” A “smart” body knows it can’t control the motion, so it limits the use of that motion to avoid the functional instability. 

The Performance System in 3DMAPS® (3D Movement Analysis & Performance System) has two (2) options that are pertinent in this example. One is Elevated Lunge Leg and the other is Elevated Stance Leg. These positions combined with bilateral hand drivers in all three planes can be the strategy for” tweaking in” and “tweaking out.” One direction in each plane will “tweak in” more hip resources, while the opposite direction will “tweak out” hip resources forcing the knee to do more work.

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