Lower limb and knee account for >75% of musculoskeletal injuries in today’s military

Osteoarthritis is among the leading causes of disability in the United States, costing billions of dollars each year in lost work hours, treatments and doctor visits, and leaving people sidelined from day-to-day activities.

Hector Alvarado wearing a knee brace from Townsend Design

By Nicole Wetsman, Lower Extremity Review May 2018

That problem is mirrored and amplified in the military, a unique segment of the population that relies heavily on physical fitness and ability. “OA is the leading cause of disability discharge from the military,” said Kenneth Cameron  PhD MPH ATC FNATA, director of Orthopaedic Research at Keller Army Community Hospital, West Point, NY. Indeed, the lower limb and particularly the knee account for more than 75% of military-related musculoskeletal injuries.

The armed forces are particularly affected by osteoarthritis, and disease often strikes soldiers earlier than it would civilians. However, management and treatment are hampered by the same information gaps as in the general OA population. Despite the urgency of the problem, which increases daily due to multiple deployments, research focused on military-specific osteoarthritis remains underfunded—even though successes in that sphere could translate out into the civilian population.

“We need to do a better job ensuring people can stay in their jobs,” Cameron said. “Anything the military does will be relevant to the general population.”

For comparison, the way post-traumatic OA is managed today would be like identifying patients with hypertension and saying that they don’t need to come back until they have a heart attack—that is, without intermediary treatment. There are no intermediary treatments for OA.

Military populations experience high rates of disability related to post-traumatic osteo­arthritis (PTOA), which does not always originate from combat injury. But military researchers are also uniquely posi­tion­ed to explore therapeutic options to minimize the effect of PTOA. Lower Extremity Review

A military readiness problem
Between 1999 and 2008, 108,266 cases of physician-diagnosed osteoarthritis were documented in the Defense Medical Surveillance System,1 which collects health-care data in the military. Just as in the civilian population, the rate of OA increases as service members get older, according to an analysis published in Arthritis & Rheumatology in 2011,1 and enlisted service members, who have more physically demanding positions, were at a higher risk of the condition. Overall, the military had nearly twice the incidence of OA compared with the general population, making OA a potential threat to military readiness.

The rate of OA remains higher than average among veterans, with 32 % of veterans reporting doctor-diagnosed arthritis, compared with 22 % of non-veterans, according to a 2006 study of nearly 125,000 adults surveyed through the Behavioral Risk Factor Surveillance System.2

Placing the right Soldiers in the right jobs, keeping them healthy and optimizing their physical performance was the focus for 325 scientists from around the world, who gathered in Boston this week for the 2014 3rd International Congress on Soldiers’ Physical Performance, to share ideas and increase efficiency in those areas. Among the topics discussed, was the effect of load carriage on health and performance. Pictured here, Spc. Arielle Mailloux gets some help adjusting her prototype Generation III Improved Outer Tactical Vest from Capt. Lindsey Pawlowski, Aug. 21, 2012, at Fort Campbell, Ky. Both Soldiers are with the 1st Brigade Combat Team Female Engagement Team, 101st Airborne Division (Air Assault). These prototypes were designed specifically for the needs of female Soldiers, with shorter torso length and other improvements. Megan Locke Simpson, Courier staff

Body-borne loads and military osteoarthritis
Heavy loads, such as body armor, heavy boots, backpacks, and weapons, affect movements of the knee in military service members, and might contribute to injury risk or osteoarthritis (OA), according to several studies represented at the recent 41st Annual Meeting of the American Society for Biomechanics.

Carrying a medium or heavy load (defined as 15% and 30% of bodyweight, respectively) affected knee-joint movements of male soldiers during a run-to-walk task but not during a walk-to-run task.1 The deceleration from run-to-walk caused soldiers who were wearing medium or heavy loads to exhibit significantly increased knee abduction and internal rotation, which might increase risk of injury and knee instability. The authors called for additional research to identify biomechanical strategies that might help soldiers avoid risky movement patterns and protect against injury during deceleration.

Exhibiting varus thrust, a biomechanical feature in which the knee bows out laterally during the weight-bearing portion of a step, puts people at increased risk of knee OA. Adding weight burden, which also increases risk of knee OA, to soldiers with this walking pattern is therefore a potential concern. However, in research discussed at the 2017 American Society for Biomechanics annual meeting, and subsequently published in the Journal of Biomechanics,2 adding a body-borne load actually reduced thrust in 9 military personnel who presented with it initially (one half the study sample). Nine military personnel without vagus thrust, however, adopted a walking pattern that were related to risk of OA, such as thrust and knee abduction, when carrying a load.

Current research underscores the complex relationship between added load and changes in biomechanics, particularly in the knee. Authors on both studies1,2 stressed the need to develop intervention strategies that might reduce movement patterns linked to the development of osteoarthritis for service members.

References
  1. Changes in knee kinetics are required for deceleration with body borne load (Abstract 009A), Cameron, SE, Kaplan JT, and Brown T, Ramsay JW. Presented at the 41st Annual Meeting of the American Society for Biomechanics, Boulder, Colorado, August 8-11, 2017. Accessed June 20, 2018.
  2. Individuals with varus thrust do not increase knee adduction when running with body borne load, Brown TN, Kaplan JT, Cameron SE, Seymore KD, Ramsay JW. J Biomech. 2018;69:97-102.

Earlier interventions needed
Treating OA in the military is no different than the challenge facing civilian clinicians. There simply aren’t many treatment options for OA outside pain management and, eventually, joint replacement.

In younger service members, like many soldiers who develop joint problems early, choices are even more limiting and difficult. “You’re really trying to navigate, how do I keep working, and manage this best I can, because I’m too young for a joint replacement,” said Kelli Allen, PhD, health services researcher at the Thurston Arthritis Research Center, University of North Carolina at Chapel Hill. “Ideally, you catch it early, and try to aggressively manage it.”

Directing research dollars
Although the military is well aware of the problem OA poses to military readiness and has a ready and well-documented population for research, funding dollars from the US Department of Defense for studies on the armed forces are often scarce. Department of Defense funding is distributed by Congress, and the pot of money is open to all researchers—not divided by disease.

“We’ve only just started to allocate research funding in the last few years,” Cameron said. “It’s become more of a priority. But it’s still a challenge because the dollars are congressionally allocated, and there’s no specific funding mechanism for osteoarthritis. We’re competing with 40 or 50 other disease categories.”

References
  1. Incidence of physician-diagnosed osteoarthritis among active duty United States military service members, Cameron KL, Hsiao MS, Owens BD, Burks R, Svodoba SJ. Arthritis Rheum. 2011;63(10):2974-2982.
  2. Arthritis prevalence and symptoms among US non-veterans, veterans, and veterans receiving Department of Veterans Affairs Healthcare, Dominick KL, Golightly YM, Jackson GL. J Rheumatol. 2006;33(2):348-354.
  3. Obesity & osteoarthritis, King LK, March L, Anandacoomarasamy A. Indian J Med Res. 2013;138:185-193.
  4. Posttraumatic osteoarthritis caused by battlefield injuries: the primary source of disability in warriors, Rivera JC, Wenke JC, Buckwalter JA, Ficke JR, Johnson AE. J Am Acad Orthop Surg. 2012;20(Suppl 1):64-69.

Source Lower Extremity Review

Also see
Post-traumatic OA: Unique implications for the military in Lower Extremity Review
International scientists discuss Soldier physical performance in Army.mil
Keller’s SportsMed Fellowship makes strides in research, care in Army.mil

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