September 2016

Offloading and obesity: Gait study data have OA implications

In the moment: Knee OA

9itm-oashutterstock_227455105By Katie Bell

Gait interventions can alter knee loading in obese patients, which may have implications for knee osteoarthritis (OA), according to three studies presented in August at the annual meeting of the American Society of Biomechanics in Raleigh, NC.

Offloading the knee during gait in obese patients can be challenging, said Joaquin A. Barrios, DPT, PhD, an associate professor in the Department of Physical Therapy at the University of Dayton in Ohio.

“Obese patients, from a clinical biomechanics perspective, often converge on movement patterns during gait that are abnormal due partly to movement restrictions,” Barrios said. “As one example, greater thigh girth may impede the thighs from passing each other freely during midstance, so proximal kinematics will organically change to allow for this clearance.”

Barrios and colleagues evaluated the effects at the medial tibiofemoral joint of both increasing and decreasing walking speed by 10% in 14 healthy participants while ambulating overground with and without a simulated 10% weight gain.

Simulated weight gain increased all loading parameters, including peak force, loading rate, impulse per step, and impulse per kilometer. Meanwhile, a faster gait speed increased the peak amplitude of the joint loads but decreased impulse per step and per kilometer due to reduced exposure time and fewer loading cycles.

“Offloading interventions should complement interventions aimed at pain and inflammation reduction, strengthening, diet, and exercise patterns, among others,” Barrios said.

A separate study also looked at velocity, specifically which combinations of walking velocity and stride length could help reduce peak knee internal extension and abduction moments in 10 obese participants. They found that decreasing velocity at the participants’ preferred or decreased stride length was the most effective combination for reducing both frontal and sagittal plane moments.

Study author Michael Bijman, MSc, a doctoral student in the Department of Physical Therapy & Rehabilitation Sciences at Drexel University in Philadelphia, noted that altering velocity and stride length would be easier for most patients than gait modifications focused on the frontal plane.

“Patient acceptance was definitely considered when designing the interventions,” Bijman said.

He hypothesized that similar effects would occur in obese patients with knee OA.

“I can only speculate, but I think similar results will be seen,” Bijman said. “A decrease in speed with a preferred or decreased stride length will result in the same findings as we presented.”

A third study, which was concurrently published in the July issue of Gait & Posture, examined the influence of obesity on the incidence of heel-strike transient, a rapid transient rise in the vertical ground reaction force (GRF) after heel strike that is indicative of a high rate of loading, which can contribute to knee OA.

The study included 30 participants, half of whom were obese and half of normal weight. When walking at a standardized speed, 53% of the obese participants demonstrated a heel-strike transient, compared with just 20% of the normal-weight participants.

The study did not look at interventions to modify heel-strike transient, but addressing arthrogenic muscle inhibition—which is common in individuals with knee pathologies—may help, according to lead author Derek Pamukoff, PhD, an assistant professor in the Department of Kinesiology at California State University, Fullerton.

“Improving quadriceps function by removing inhibition may be a suitable strategy for attenuating ground reaction force during walking,” Pamukoff said.

The authors suggest further study to examine factors that may affect the incidence of heel-strike transient, such as quadriceps function and walking speed, and to evaluate the influence of heel-strike transient on knee OA development.

Sources:

Barrios JA, Wilson JD, DiLiberto FE, et al. Effects of altered walking speed and simulated weight gain on medial tibio­femoral joint contact force para­meters. Presented at 40th Annual Meeting of the American Society of Bio­mechanics, Raleigh, NC, August 2016.

Bijman MP, Milner CE. The influence of walking velocity and stride length on the knee in obese adults. Presented at 40th Annual Meeting of the American Society of Biomechanics, Raleigh, NC, August 2016.

Pamukoff DN, Dudley RI, Vakula MN, Blackburn JT. Greater incidence of heel strike transient in obese compared to normal weight adults. Gait Posture 2016;49:181-183.

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