July 2015

Extra bodyweight enhances effects of high heels at knee

Lower heels, BMI may reduce OA risk

7FOOT-high-iStock19230018-copyBy Emily Delzell

Walking in shoes with heels higher than about 1.5 inches causes gait abnormalities that are amplified by extra bodyweight, according to recent research that found high-heeled walking creates significant changes in knee loading similar to those seen in knee osteoarthritis (OA).

Using a shoe that converts through a retractable heel from a height of 3.8 cm (1.49 inches) to 8.3 cm (3.26 inches) and a standard half-inch-drop athletic shoe, investigators from Stanford University in Cali­­fornia asked 14 healthy normal-weight women to complete 10-m marker-based gait trials in shoes of each height and under several conditions. These conditions included walking at their preferred speed with and without a weight vest equal to 20% of their bodyweight and walking slower than preferred and faster than preferred without the vest.

The investigators calculated measures of knee flexion angle and knee extension and adduction moments, normalizing external joint moments to percent bodyweight and shoe height. Weighted trials were normalized to percent bodyweight plus vest weight and shoe height.

Walking speed declined significantly with heel height, but wasn’t affected by weight. At preferred walking speed, knee flexion angle at heel-strike and midstance increased with increasing heel height and weight. Maximum knee extension moment during loading response decreased with added weight; maximum knee extension moment during terminal stance decreased with heel height; and maximum adduction moments increased with heel height.

The results support the concept of a threshold shoe heel height above which aberrant loading patterns at the knee are amplified.

The investigators also found a threshold effect with heel height, noting a significant increase in maximum knee flexion moment for the higher heel compared with the control shoe and no significant change with the lower heel compared with the control.

“High heeled shoes cause a myriad of foot problems. What is less appreciated is that walking in high heels also changes forces across the lower back, hips, knees, and ankles,” said study lead author Constance R. Chu, MD, professor and vice chair of research in Stanford’s Department of Orthopedic Surgery. “We measured the compensatory forces across the knee and found increases similar to what people with the most common forms of knee osteoarthritis have. The abnormal forces were eliminated by wearing [the control shoe] and nearly eliminated by wearing a 1.5-inch ‘kitten’ heel.”

Chu and her colleagues didn’t control for foot type, but she noted that foot deformities can magnify abnormal forces, not only across the foot, but also through the knee and other joints during gait.

“The larger knee adduction moment with increasing heel height is very interesting because increases in this value have been linked to progression of knee OA on the medial side,” said Neil Cronin, PhD, a senior researcher at the Neuromuscular Research Centre at the University of Jyväskylä in Finland. “But we don’t yet know how repeated use of high heels affects cartilage health. Determining what is actually happening to the structure of the tissues around the knee joint would take us a step closer to being able to really link high heel use with increased risk of OA.”

Both Chu and Cronin said the findings emphasize that additional bodyweight is associated with changes in knee joint mechanics that are similar to those seen in knee OA.

“Overweight women who wear heels regularly could increase their risk of developing OA more so than people who are not overweight,” said Cronin.

Chu and her colleagues noted in the paper, published in the Journal of Orthopaedic Research in March, that their data support the existence of a threshold heel height at which aberrant loading patterns are amplified.

“There is now a growing body of evidence to support this statement,” said Cronin. “It may be that by simply wearing lower heels—about four centimeters, for example—a woman can significantly decrease her risk of various negative side effects. This could include OA, but also other symptoms such as leg and back pain, balance problems, and foot and toe deformities.”

The Stanford group documented within-group variability among participants’ movement patterns, finding increased maximum flexion knee flexion moment with the higher heel after correcting for speed.

“We observed a slower preferred gait when subjects walked in heels that reduced some aberrant loading patterns,” said Chu.

This variability suggests that different women adapt to shoes in different ways, said Cronin, noting this study and others have had small sample sizes.

“We really need bigger studies to account for this [variability],” he said.

Source:

Titchenal MR, Asay JL, Favre J, et al. Effects of high heel wear and increased weight on the knee during walking. J Orthop Res 2015;33(3):405-411.

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