Muscle weakness while walking may contribute to unstable joints

Analysis showed people with hEDS produced less force while extending hips

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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People with hypermobile Ehlers-Danlos syndrome (hEDS) produced less force when extending their hips during walking and had weaker muscles associated with hip extension compared to healthy people, according to a recent analysis.

Researchers believe this muscle weakness may contribute to joint instability and related joint damage that tends to accrue in people with hEDS. Nearly three-quarters of hEDS patients reported that they experience hip subluxations — joint misalignments, or partial dislocations — at least once per week.

“Our findings may help clinicians establish an understanding of potential biomechanical- and muscle-related targets for interventions to improve gait mechanics and to help increase physical activity, optimize joint function and reduce risk of joint degeneration in the hEDS population,” the researchers wrote.

The study, “Assessment of gait mechanics and muscle strength in hypermobile Ehlers Danlos Syndrome,” was published in Clinical Biomechanics.

Among the symptoms of hEDS, a connective tissue disease, are joints with an unusually large range of motion (joint hypermobility).

Ensuing instability makes hEDS patients especially prone to joint dislocations and tissue injuries during movement, with hEDS patients at an elevated risk of joint damage and degeneration, or osteoarthritis. Moreover, these injuries contribute to chronic fatigue and pain.

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Scientists evaluated differences in gait, muscle strength

Limited research has evaluated the impact of joint hypermobility on gait patterns and muscle function in hEDS. Such studies are needed to help doctors understand the effects of hEDS on joint function while walking, in turn informing the development of rehabilitation strategies to prevent joint damage in this population, according to the authors.

To that end, the scientists aimed to evaluate the differences in leg and ankle gait mechanics and muscle strength among hEDS patients relative to healthy people. Their analysis involved 11 hEDS patients (nine female patients) with a mean age of 36.4 years, as well as 11 healthy people, who served as a control group.

All participants underwent a three-dimensional gait analysis. Equipped with reflective markers to track joint positioning during walking, participants were asked to walk on a treadmill at a self-selected pace in short, 20 second bursts.

Assessments of hip and knee muscle strength also were collected, and hEDS patients self-reported on the occurrence of joint subluxations.

Gait analyses indicated hEDS patients and controls walked at similar speeds and had generally similar joint movements, or kinematics, across the hips, knees, and ankles.

Still, the hEDS patients walked with a lower peak hip extensor moment than controls. Essentially, that means that the soft tissues (e.g., muscles, ligaments) involved in hip extension exerted less force during walking relative to healthy people. Hip extensor muscles, mainly the hamstrings (back of thigh) and gluteus maximus (buttocks), help propel the body during movement.

Correspondingly, the strength of the hip extensor muscles was significantly lower in hEDS than that observed in the control group by 40%.

“The lower peak hip extensor moment observed in the hEDS cohort may be due to the hip extensor weakness in these hEDS individuals and may lead to joint pain and instability during walking,” the researchers explained.

Nearly all (91%) of hEDS patients reported that they experienced hip, knee, or joint subluxations at least once weekly. Specifically, 73% reported frequent subluxations in the hips, while regular knee and ankle subluxations were reported by 55% and 45% of patients, respectively.

The scientists noted that altered hip extensor function during gait may contribute to instability of the hip joints, in turn contributing to the high observed rates of hip subluxations.

Altogether, such hip issues “may hinder the ability of people with hEDS to carry out daily tasks or exercise and could have a negative impact on their overall general wellness,” the researchers wrote.

The scientists believe it is likely that weakened hip muscles in hEDS patients are related to altered muscle composition in these individuals.

“Future work combining measures of hip extensor muscle composition and gait analysis would provide insight into the potential underlying compositional factors associated with hip extensor muscle dysfunction that lead to altered hip extensor moments in the hEDS population,” the scientists wrote.

The team also indicated that future studies should include larger groups of patients, longer walking times, and studies of the electrical activity of muscles during exercise.