Including injury history adds to value of FMS

Multiple studies indicate that poor movement, as assessed using the Functional Movement Screen, and past history of injury are risk factors for future injury, and a recent investigation suggests that risk is compounded in athletes with a combination of those two factors.

By MAJ Michael Garrison, PT, DSc, OCS, SCS; and MAJ Richard Westrick, PT, DSc, OCS, SCS

Injuries related to sports, recreation, and exercise are significant issues for athletes at all skill levels. Injuries can lead to time away from sports and exercise or reduce an athlete’s performance level. The healthcare system is equally burdened by such injuries. It is estimated that more than 3.2 million emergency department visits across the US for children younger than 14 years are due to sports or exercise injuries.¹ This figure underestimates the true impact on the healthcare system, because the majority of those with less serious injuries present not to emergency departments but to primary care physicians, orthopedists, or physical therapists.

The financial impact of these injuries can be better appreciated by considering one common sports injury. The management of anterior cruciate ligament (ACL) tears costs more than $2 billion annually in the US.² This figure includes diagnosis, surgical man­agement, and subsequent rehabilitation costs. Considering that approximately 70% of ACL injuries result from a noncontact mech­anism, a large percentage of these injuries may be preventable. Relative risk reduction calculations reveal a prophylactic benefit to neuromuscular retraining programs for the prevention of ACL injury. However, numbers-needed-to-treat analysis indicates that approximately 100 participants need to complete a training program to prevent just one ACL injury.³ Identifying athletes who are at highest risk for injury prior to implementing preventive programs is a major priority.

Practitioners often perform screening tests on asymptomatic populations to identify those who may be at risk for developing a particular condition. These tests may help identify issues early in the process and potentially lead to intervention programs that help prevent the onset of injury or illness.

Several properties enable effective use of a screening test. The test should maximize sensitivity to ensure that participants at a higher risk of injury are identified and progressed on to the next level of assessment. The test needs to be easy to use and relatively inexpensive. Individuals administering the test should be able to do so without the need for advanced training. Because musculoskeletal injuries are multifactorial in nature, a fourth factor that is specific to screening for these conditions is that the test needs to look at multiple intrinsic risk factors. The Functional Movement Screen (FMS) meets all of these criteria, and published studies report good reliability when the same team of examiners is used.^4-7

The Functional Movement Screen

The FMS is an objective screening tool consisting of seven movement tests. The tests are the hurdle step, deep squat, in-line lunge, shoulder mobility, active straight-leg raise, rotary stability, and stability push-up. Test scores range from 0 to 3 for each test; 21 is the highest total composite score. Examiners can collect asymmetry measures for the five tests that measured scores for each individual side. All participants perform each movement up to three separate times, with the highest score of the three movements collected. The screening examination is described in excellent detail in other publications and the reader is encouraged to reference these studies for more information.⁷

In 2007, Kiesel et al published findings indicating a relationship between a low FMS score and incidence of serious injury on a professional US football team.⁸ They determined that a composite FMS score at or below 14 predicted injury in this cohort of professional athletes. However, there are several limitations to this study to consider prior to implementing the findings.

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The study was retrospective, which limits its internal validity. Additionally, injury was defined as placement on the injured reserve list and a time loss from practice or competition of at least three weeks. There are many injuries, however, that significantly impact performance but don’t result in such substantial time losses. The authors are certainly correct when emphasizing in their title (“Can serious injury in professional football be predicted by a preseason functional movement screen?”) that these results are predictive of serious injury. Another significant limitation involves the reliability of reporting for the FMS measurements. FMS scores are often considered on a scale of 0 to 21, but in reality the scale is much tighter, as asymptomatic athletes typically don’t score below 10, and rarely is someone perfect with all seven movements. In this particular study, the FMS scores ranged from 10 to 20. When the scores are in a tighter range, the reliability of the scoring system becomes more important, as even small irregularities can greatly impact results. The retrospective nature of this study also indicates that screening procedures may not have been standardized for all participants and examiners, which again can greatly impact results.

Chorba et al in 2010 and O’Connor et al in 2011 conducted similar studies looking at the relationship between injury development and movement screening.^9,10 Chorba et all utilized a small sample population (n = 38) and considered only female athletes participating in fall sports. Their results suggest that the cutoff score of 14 or less is predictive of lower extremity injury in female athletes. O’Connor et al looked at a large number of male Marine Corps officer candidates (n = 874) and found that scores of 14 or less were predictive of injury, though the sensitivity of the screen was undesirably low. Only 10% of their study population scored 14 or below, and the study relied on medical visits for injury reporting. A highly motivated cohort of men, already self-selected as US Marines, limits the generalizability of the study findings; recent evidence suggests that approximately 50% of musculoskeletal injuries are unreported by military service members.¹¹

Our research

In designing our study,¹² we considered all these issues to improve both internal and external validity. Our study was prospective in nature, with screening tests planned well in advance and reliability reported. The same team of examiners was used for all athletes to ensure consistent grading of the seven FMS tests. We included both male and female athletes (n = 160) involved in contact and noncontact sports. Our contact sports included rugby (male and female) and soccer. Noncontact athletes participated in swimming and diving. We also included a broad definition of injury to ensure we captured all medical events that might impact overall performance, and we used redundancies in injury tracking to ensure that we captured all incidents requiring medical attention. These redundancies included medical record screening, interviews with team athletic trainers, and monitoring of our institution-specific injury tracking data.

Our data indicate that maximal sensitivity for injury screening is achieved by asking participants to self-report any history of injury over the past 12 months. The sensitivity of that question alone was 72% in our cohort. The problem with sensitivity measures for past history of injury in isolation is that they do not allow a clinician to determine the probability that an athlete with this risk factor is likely to be injured again. A highly sensitive test is useful when ruling out a condition, whereas a likelihood ratio is a more accurate measure with immediate applicability; a higher likelihood ratio indicates a greater likelihood of injury development.

In our cohort, combining a self-report of past injury with a movement score of 14 or below maximized sensitivity and produced a likelihood ratio of 5.88. These combined factors also generated the lowest negative likelihood ratio, which is the ideal scenario for a useful clinical test. In our study population, the pretest probability of injury development was 33%. Applying our injury prediction rule increased the post-test probability of injury development by 41%. In other words, 74% of the study participants who met our increased injury risk criteria experienced some type of injury during our data collection period.

To analyze the predictive power of the FMS combined with past history of injury, we conducted a logistic regression analysis. The generated odds ratio (OR) of 15.11 indicates that an athlete with a past history of injury combined with a poor movement score has a 15-times higher risk of injury than his or her teammates. The odds ratio generated from both factors together (OR = 15.11) is larger than the individual odds ratios for poor movement (OR = 5.61) and past history of injury (OR = 3.45) added together.

Clinical implications

The clinical implication of this finding is obvious. An athlete with poor movement and a past history of injury needs to be assessed by a healthcare provider to determine if a specific intervention can decrease his or her injury risk. A sports-trained healthcare provider is uniquely qualified to perform that assessment and implement an injury reduction program.

The finding that history of injury is a risk factor for future injury is consistent with multiple previous studies.^13-15 This continues to indicate that individuals are returning to athletic endeavors before they are fully recovered from a previous musculoskeletal injury, or without having addressed the movement-related risk factors that contributed to the initial injury. Screening for history of injury with a patient self-report and a basic movement examination can help identify those that require further assessment. In an asymptomatic population, this screening can be conducted prior to the implementation of an offseason conditioning program. Team medical personnel can assess those identified as being at elevated risk of injury to formulate individualized approaches to address those athletes’ deficits.

In situations involving a large group of athletes or when medical resources are limited, efforts can be focused on screening only those with an identified history of injury. But, if possible, participants with a combination of injury risk factors should be the first priority, as they are most at risk. Movement screening can also be valuable when progressing postoperative patients back to sports participation. When considering return to sport after lower extremity surgery, there is a clear need for objective criteria, and movement-based screening may have the potential to address that need.

An example

Again, one can consider ACL injury as an example. A tear of the ACL is a very common, but serious, sports-related injury. For competitive athletes participating in cutting, twisting, and pivoting sports, a reconstruction of the ACL is often recommended in the presence of recurrent instability.¹⁶ The deleterious effects of sports participation with an unstable knee include meniscal damage, articular cartilage injury, and damage to secondary ligamentous stabilizers. While most athletes will return to some level of sports participation after ACL reconstruction, studies show the percentage who return to their preinjury level of competition can be as low as 33% to 44%.^17,18 In another study, less than 50% of the study sample returned to full sports participation up to seven years after surgery.¹⁹

There is also growing concern regarding the rate of second ACL injury when returning to sport after primary ACL reconstruction. Some studies report a six-times greater risk of second ACL injury (ipsilateral or contralateral to the initial tear) within two years of ACL reconstruction, compared with a group of healthy controls.²⁰ For Division I athletes returning to high-level competition, the rate of second ACL injury in the contralateral or ipsilateral limb is as high as 37%.²¹ The inability to fully return to preinjury level of competition and the high rate of reinjury indicates that current rehabilitation protocols are not adequately measuring or addressing some component of overall function.

Objective criteria for return to sport after musculoskeletal injuries such as ACL tears are rarely used.²² Most postoperative rehabilitation protocols base progression on easily assessed clinical measures such as range of motion, effusion, and laxity. The vast majority of protocols are time-based, meaning postoperative patients are progressed to the next stage of rehabilitation based simply on duration of time from surgery rather than on any consistent objective measure of function.

In a recently published study, Mayer et al tested patients to determine if a difference existed between patients who were cleared for sport after ACL reconstruction and those who were not.²³ Patients in the cleared-to-return group met basic clinical exam criteria, including measures of laxity, motion, and strength. There was no statistically significant difference in composite FMS scores between the two groups (12.72 vs 12.83). The FMS composite scores for both groups also fell well below established normative values.²⁴ Average FMS composite scores below 14 combined with history of injury put both the cleared-to-return group and the noncleared group at an elevated risk of injury. This study highlights that clinical measures alone are insufficient in measuring certain aspects of dynamic control that might be important for making a full return to sport participation; including movement-based assessments such as FMS testing in return-to-play protocols may help to address this issue.

Conclusion

Functional movement is a hot topic in sports medicine. We must be cautious about accepting literature results that might be influenced by personal or commercial bias. However, putting that aside, multiple studies do indicate that poor movement and past history of injury are risk factors for future injury. Combining these two factors seems to compound this risk. A standardized, objective, and reliable method of measuring movement is needed as we move toward implementation of effective intervention strategies. Measuring functional movement should be considered prior to offseason athletic conditioning and prior to clearing an athlete for return to sport following musculoskeletal injury.

MAJ Michael Garrison, PT, DSc, OCS, SCS, is a graduate of the US Army-Baylor University Sports Physical Therapy Doctoral Program in Waco, TX, and currently serves as the director of physical therapy services for the US Army installation at Fort Carson, CO. MAJ Richard Westrick, PT, DSc, OCS, SCS, is a graduate of the US Army-Baylor University Sports Physical Therapy Doctoral Program and currently serves as the chief of the Environmental Medicine Branch at the US Army Research Institute of Environmental Medicine in Natick, MA.

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