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20-10-2011 | Sports medicine | Article

Hip, knee movement may protect ankles during jumps


Free abstract

MedWire News: Reduced variability in hip and knee movements when landing a jump may explain why some individuals experience repeat ankle injury, while others make a full recovery, US researchers suggest.

"One theory for explaining those divergent paths is that a person comes up with good strategies to move, land, balance and not get re-injured," commented lead author Cathleen Brown (University of Georgia) in a press release.

However, the team is unable to say if ankle injury leads to a reduction in proximal joint movement or whether the lower variability in hip and knee movement increases the risk for ankle damage.

The researchers recruited recreational athletes with mechanically (n=21) or functionally (n=23) unstable ankles, defined as one or more moderate-severe ankle sprain at least 12 months ago that resulted in at least 3 days of immobilization, reports of giving way two more times in the past 12 months, and a score of 25 or less on the Cumberland Ankle Instability Tool (CAIT).

These participants were compared with 20 "coper" athletes - individuals with one moderate-severe ankle sprain, a CAIT score of 25-28, and no episodes of giving way - and 24 athletes without ankle injury (controls).

The participants underwent 10 single-leg landings from a 50% maximum vertical jump while kinematics and ground reaction forces were measured for ankle, knee, hip, and trunk motion.

As reported in the journal Clinical Biomechanics, controls had significantly more variability in their knee rotation than both functionally unstable patients and copers before initial contact, and more variability in knee rotation during stance than functionally unstable patients.

Controls also showed more variability in stance for hip flexion than functionally unstable participants during lateral jumps, and anterior hip abduction compared with mechanically and functionally unstable participants.

Controls also showed more variability than other participants for hip flexion, and for hip abduction compared with mechanically unstable individuals.

"Inability to effectively utilize proximal joints to perform landing strategies may influence episodes of instability," Brown et al suggest.

By Lynda Williams

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