SAN DIEGO — Runners who were experiencing chronic back pain were at least twice as likely to develop knee pain as those without chronic back pain. The finding was based on data from more than 400 adults.
Runners who experience one injury often have concurrent musculoskeletal pain or injury elsewhere that will inhibit their recovery if unrecognized and untreated, said Kevin R. Vincent, MD, of the University of Florida, Gainesville, in a presentation at the American College of Sports Medicine (ACSM) 2022 Annual Meeting.
"When a runner comes in with pain, look beyond the area that hurts," because a patient often develops biomechanical patterns to compensate for the injury, Vincent told Medscape Medical News in an interview.
Vincent and his wife, Heather K. Vincent, PhD, also of the University of Florida, Gainesville, observed that runners who presented to their clinic with chronic back and sacroiliac pain also reported patellofemoral pain (PFP) during their clinical and sports performance workups, but an association between the two areas had not been well studied.
Drs Vincent and Vincent conducted a cross-sectional analysis of runners who were treated at the University of Florida Health Running Medicine Clinic.
The study population included 478 adults. The average age of the patients was 35 years, and they had an average of 10.6 years of running experience. Approximately half were male, and 90% were White. Approximately one third said they were training for a race at the time of the study, and the average weekly mileage was 33 km (20 mi).
"The knee pain was not what brought them to the clinic, but the pain was present," Heather Vincent told Medscape in an interview. "After careful observation and review, we recognize for some of these runners with back and knee pain that there may be common motion features that relate to this pain combination," she said.
Study participants underwent complete medical histories, as well as motion analyses and kinetics measures on a treadmill.
The primary outcome was PFP in runners with a history of low back pain, for which there was a statistically significant odds ratio of 2.54 (P = .028) in a logistic regression analysis that controlled for factors including age, sex, weekly mileage, and years of running.
The participants were divided into four groups: those with low back or sacroiliac pain, those with PFP pain, those with both low back and PFP pain, and those with neither, who served as controls.
Several key biomechanical features stood out among the runners with low back pain who went on to develop PFP, Kevin Vincent said in his presentation. "They ran stiffer," he said. The runners with chronic back pain changed their biomechanics to protect the low spine and to manage the pain, which translated into significantly different measures of stance time, vertical average loading rate, anterior pelvic tilt, peak ankle abduction, and range of motion for hip flexion and extension compared to patients in the other groups.
The investigators observed no other differences among the four groups in terms of weekly volumes of strength training or aerobic cross training that might explain the difference in pain patterns, he noted.
The study findings were limited in part by the study's cross-sectional design, Heather Vincent told Medscape Medical News in an interview. "These biomechanical data were collected from runners during a snapshot of time, and the historical information from injuries and onset of other musculoskeletal pain was reported by the patient," she explained.
"It would be ideal to catch runners at the first onset of back pain and prospectively follow them over the course of the natural evolution of the pain — which runners got better and why, and which runners continued to worsen and develop other pains and why," Heather Vincent added. "The relative scarcity of prospective tracking is an important limitation to a lot of running-related research as we try and discover mechanisms underlying certain injury trajectories," she said.
"Establishing clear pathways of outcomes with the factors that affect these outcomes, such as participation in physical therapy, changes in running volume or form, use of medications, cross training, and shoe wear, may all contribute to the pain trajectories. A breakthrough in running science could come if we could clearly delineate which therapeutic pathway, or lack thereof, contributes to onset of other pains after the first one develops," Heather Vincent added. "When runners continue training despite pain, invariably there are compensatory biomechanics that emerge somewhere along the kinetic chain."
The biomechanic measurements suggest that runners with both back and knee pain are hitting the ground harder and with more spinal stress, creating a stiffer landing over a relatively longer period, Heather Vincent explained. Interventions might include core strengthening and abdominal bracing to prevent excessive pelvic tilt, as well as gait retraining strategies to shorten steps and promote softer landings, along with lower body strength training, she said.
"When engaging in patient encounters for running-related back pain, ask about knee pain or pain further along the kinetic chain to determine whether or not there are compensatory actions occurring," Heather Vincent advised. "Given that we found that runners with back pain are 2.5 times as likely to have concurrent knee pain, we don't want to only partially treat the runner. Obtain pain ratings from major joints and the time course of when it occurred. Develop care plans that take concurrent pain into account, not just the pain that brought the runner to the clinic," she said.
Look at the Whole Person
The study is important as a reminder to clinicians to consider the big picture, said Zoey Kearns, MS, of the University of Memphis, who served as a co-chair for the session.
"We spend a lot of time looking at one body part," she said. Often in clinical practice, "everyone gets focused on their specialty; it is easy to forget about what else is going on" and to forget that everything is connected along the kinetic chain, she added.
The findings from the current study were not surprising, but the biomechanical data provide a concrete measure of some concepts that are known anecdotally and are "a reminder that patients are not models on a computer," Kearns said. "If you go in for treatment of knee pain that doesn't resolve, you haven't dealt with the root of the problem," she noted.
The message for clinicians, said Kearns, is "understanding that pain doesn't happen in isolation and understanding the root cause rather than just treating the symptoms."
Kevin Vincent, Heather Vincent, and Kearns have disclosed no relevant financial relationships.
American College of Sports Medicine (ACSM) 2022 Annual Meeting: Abstract 57. Presented June 1, 2022.
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Cite this: Heidi Splete. Chronic Back Pain Could Be Behind Runners' Knee Problems - Medscape - Jun 02, 2022.