Objective To prospectively determine risk factors contributing to the development of exertional medial tibial pain (EMTP).
Methods Data were prospectively collected on healthy female students in physical education, who were freshmen in 2010–2011 and 2011–2012. Eighty-six female students aged 19.38±0.85 years, were tested at the beginning of their first academic year. Kinematic parameters in the frontal and transverse plane were measured during a single-leg drop jump (SLDJ). For further analysis, the SLDJ task was divided in two phases: touchdown until maximal knee flexion (MKF) and then MKF until take-off, representing landing and push-off phase, respectively. The injury follow-up of the students was assessed using a weekly online questionnaire and a 3-monthly retrospective control questionnaire. EMTP was diagnosed by an experienced medical doctor. Cox regression analysis was used to identify the potential risk factors for the development of EMTP.
Results During injury follow-up (1–2 years), 22 participants were diagnosed with EMTP. The results of this study identified that increased range of motion (ROM) in the transverse plane of hip and thorax during landing (p=0.010 and 0.026, respectively) and during push off (p=0.019 and 0.045, respectively) are predictive parameters for the development of EMTP in women.
Conclusions Increased ROM values of hip and thorax in the transverse plane, which can be interpreted as impaired ability to maintain dynamic joint stability resulting in increased accessory movements, are significant contributors to the development of EMTP in women.
- Lower extremity injuries
- Sporting injuries
- Women in sport
- Core stability/pelvis/hips, ribs
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Approximately 50% of all sports injuries are secondary to overuse.1 One of the most common overuse injuries is exertional medial tibial pain (EMTP),2 especially in female athletes.3–5 EMTP is characterised by exertional pain along the posteromedial border of the middle and distal thirds of the tibia6 and can include diagnostic entities of medial tibial stress syndrome, tibial stress fracture, chronic exertional compartment syndrome and muscular and tendon injuries.7 ,8 As generally described in literature, EMTP results from repetitive microtrauma which causes local tissue damage,1 and commonly this mechanism occurs during regular physical activity like running. However, EMTP may also develop in athletes involved in jumping sports such as basketball, tennis and volleyball.9 Regular physical activity is generally known for its positive effects on physical and mental health,10 ,11 but brings along an increasing risk of sport injuries. Such sports injuries can lead to prolonged inactivity, a need for costly therapies12 and even to chronic disability.13 The development of prevention and rehabilitation strategies for lower extremity injuries including EMTP therefore is of great concern for researchers and healthcare professionals.
Current literature has pointed out influences of distal and proximal factors in the development of EMTP, 3 ,14–16 suggesting that potential contributors can be found from the ground up and/or from the pelvis down. Concerning the distal parameters, generalised excessive or prolonged foot pronation has been described to result in numerous functional changes to the lower limb, affecting the lower leg and possibly resulting in EMTP.3 ,17 More recently, attention has turned to the role of proximal factors in the altered biomechanical function of the lower limb and in the development of lower extremity injuries like EMTP. 14 ,16 ,18–20 In order to control more distal movement, core stability has been described as being essential. 15 ,18 ,21 ,22 The impaired function of this lumbopelvic-hip complex is believed to increase vulnerability to uncontrolled joint displacements or accessory movements throughout the lower kinetic chain23 and has been shown to contribute to the development of EMTP. 24 These uncontrolled joint displacements can result in altered lower limb movements and in specific running or jumping styles. In addition to these possible altered movement strategies, Lawrence et al25 showed that participants with strong hip external rotators demonstrated significantly lower vertical ground reaction forces during single-leg landing, hence it can be speculated that decreased function of these hip muscles results in higher vertical ground reaction forces during single-leg landings.
In contrast to the well-identified distal contribution of an excessive or prolonged pronation pattern in EMTP, 3–5 ,14 no consensus on the specific contribution of proximal kinematic factors in lower extremity overuse injuries can be found in current literature.26 ,27 In a study by Souza and Powers26 increased internal femoral rotation was demonstrated in patients with patellofemoral pain syndrome, however another similar study by Willson and Davis27 revealed greater external femoral rotation. This inconsistency can be interpreted as an indication that it may be important to evaluate functional output measures like the ability to maintain dynamic joint stability (DJS) during functional activities, besides evaluating point output measures like peak kinematic parameters.26 ,27 DJS may operationally be defined as the ability of the joint to maintain position or intended trajectory.28–31 The maintenance of DJS along the entire kinetic chain seems to be important in the prevention of injuries.32
For the purposes of this study, the single-leg drop jump (SLDJ) was chosen to evaluate this ability to maintain DJS. Increased range of motion (ROM) in the frontal and transverse plane during the SLDJ can be seen as accessory movements, since the lower limb and trunk movements during this jump are located in the sagittal plane.33
The role of DJS factors in the development of EMTP remains unclear since no comprehensive and prospective research has been carried out on these parameters.3 ,14 ,15 Moreover, the link between vertical ground reaction forces during single-leg landings and the development of EMTP has not been identified so far.
Therefore, the purpose of this prospective investigation was to identify risk factors for the development of EMTP. More specifically, we analysed DJS parameters of ankle, knee, hip and lumbo-pelvic joints in the frontal and transverse plane and vertical ground reaction forces during an SLDJ. We hypothesised that female athletes with less ability to control the lower extremity movement, which results in increased accessory movements in the evaluated joints, are at risk of developing EMTP. Additionally, we hypothesised that higher vertical ground reaction forces during SLDJ would be identified as a risk factor for EMTP.
Participants were 86 female students, who were freshmen in 2010–2011(n=46) and 2011–2012(n=40) in Physical Education at Ghent University, Ghent University College and Ghent Artevelde University College, Belgium. Mean age of these students was 19.38±0.85 years. All signed informed consent and knew the goals of the study. Exclusion criteria for participating in the study were: (1) pain, ache or soreness in the lower extremity within the previous year (with specific attention for pain on palpation along the distal two-thirds of the tibia), (2) surgery of the lower extremity, (3) neurological problems that would affect lower extremity function.
At the beginning of the academic year, full-body kinematics during SLDJ of the students was assessed. Freshmen in 2010–2011 were followed throughout two academic years and freshmen in 2011–2012 were followed throughout one academic year. During their education, the participants followed a similar sports programme, under similar environmental conditions, for 29 weeks per academic year. In addition to this basic sports programme, the amount of extramural (physical activities beyond sports lessons at school) and non-supervised practice activities was also registered. This individual amount of sport participation was then used as time at risk for every student.
After the injury follow-up period, 79 of the 86 participants were taken into account for statistical analysis. Seven students developed other lower extremity injuries and therefore were excluded from the study.
The injured leg of the participants who developed EMTP was used in the statistical analysis. If an injured participant developed bilateral symptoms, the ‘most painful’ leg based on visual analogue score was taken into account. Those 22 injured legs were matched with legs of the control group. The percentage of observed dominant legs in the control group was matched with the percentage of observed dominant legs in the injured group so that leg dominance would not play a role in the statistical outcome. Therefore, one leg per participant of the control group was eliminated at random until the number of non-dominant/dominant legs of the injured group was also present in the control group (figure 1).
The SLDJ was believed to be advantageous as evaluation tool because: (1) a single-leg task is adequate in order to evaluate lower extremity movement control in the transverse and frontal planes15 ,34; (2) numerous physical activities and athletic events require brief but dynamic moments of single-leg stance35; (3) the test had to be challenging concerning eccentric, concentric and dynamic stabilising demands36 in order to screen athletes for risk factors. (4) Moreover, there was no need for an expensive treadmill or a large room with standardised running distance in order to execute the SLDJ. Before the actual SLDJ testing procedure, weight, height and leg dominance were determined. The determination of leg dominance was operationally defined as the leg preferred to kick a ball. Subsequently, three-dimensional kinematic data were collected using six Oqus cameras and Qualisys Track Manager software (Qualisys AB, Sweden). The ground reaction force data were recorded by a 1 m force plate (AMTI, USA) that was mounted flush in the middle of the wooden running track on which the SLDJ was performed. Ground reaction force and kinematic data were collected synchronously at 1000 and 200 Hz, respectively.34
Prior to the actual jump testing, the three following procedures took place: (1) marker placement, (2) standing calibration trial and (3) warming-up procedure. Marker placement during this protocol, was based on the Liverpool John Moores University lower limb trunk model (table 1 and figure 2).37
After the standing calibration trial, a functional warm-up procedure protocol of 5 min of cycling on a cycle ergometer and 20 submaximal single-leg jumps was performed.
Thereafter, the investigator demonstrated the actual SLDJ and the participants performed two practice trials per side so they would feel comfortable to complete the task. Participants were asked to stand on a box of 30.5 cm height, with both feet in a natural position. They were instructed ‘stand on your right/left leg and drop off the block, land on your left/right leg on the force plate and immediately jump as high as possible’. The SLDJ was executed three times per side. Height of the box was chosen based on previous literature38 and common use during rehabilitation and training exercises.
Further analysis of kinematic data was carried out using Visual3D software (C-motion Inc, Germantown). Raw marker positioning was low-pass filtered at 15 Hz with a second order, bidirectional Butterworth filter with padded endpoint extrapolation. Joint angles of foot up to pelvis segments were calculated with reference to the proximal segments and additionally segment angles for the pelvis39 and thorax were referenced to the lab coordination system. An X–Y–Z Euler rotation sequence was used.40 The SLDJ was divided into two phases: touchdown (TD) until maximal knee flexion (MKF) and then MKF until take-off (TO), representing landing and push-off phase, respectively. Kinematic variables of interest were DJS parameters of foot, knee, hip, pelvis and thorax segment during TD-MKF and during MKF-TO. More specifically, ROM values were measured as the difference between maximum and minimum peak values in the frontal and transverse plane, during the SLDJ. An increased value of this ROM was described as an impaired ability to maintain DJS in this study.41 In addition, vertical ground reaction forces during SLDJ were analysed. Kinematic and force parameters analysed in this study were found to exhibit good to excellent reliability (intraclass correlation range 0.65–0.96).42
Injury registration and diagnostic criteria
Since injury registration method and diagnostic criteria are very important in the recording of injuries,43 a multilevel registration method and accurate diagnostic criteria were used.
A primary online registration method was used to look for students with lower leg pain or dysfunction, but final diagnosis was always confirmed by an experienced medical doctor (MD). For this primary online method, the participants received a weekly reminder by email to register their injuries in an online questionnaire. In this online survey, the students could register their injuries, of which the localisation and other features could be specified. Once they registered lower leg for localisation of their injury, the participants were asked to visit the MD for further diagnosis. One fixed day every week the MD attended the university and the participants could ask for a free consult. As a secondary registration method, participant interviews were conducted one-on-one in a quiet and private surrounding to double-check for the occurrence of EMTP every 3 months.
The diagnosis of EMTP was performed by the MD through the following criteria: (1) an atraumatic occurrence of at least 1 week of medial tibial pain, exacerbated by running, (2) the presence of focal or diffuse palpation tenderness at the distal two-thirds of the posteromedial tibial border, (3) pain, ache or soreness of the posteromedial tibial border with possible functional limitation during physical active participation.7 ,43
Cox regression analysis (enter method) was performed to look for significant contributors to the development of EMTP. Variables with p<0.05 in the Cox regression analysis, were seen as significant predictors for EMTP. This approach has been chosen because this regression analysis assumes that risk factors affect injury in a proportional manner across time. Moreover, this method can adjust the fact that the amount of sport participation can vary between participants.13 The time of sport exposure was measured from the start of the follow-up period until the injury, or the end of the follow-up period for students who were not injured or who dropped out of the education. In case of drop-out, the date of the drop-out was taken into the account for the individual time of exposure. Statistical analysis for this study was performed using SPSS (V.21.0), except for the calculation of the thresholds for altered ROM values, which may precipitate EMTP. To define these threshold values, a receiver operating characteristic (ROC)-curve analysis was performed using MedCalc—software.
During the follow-up period, 22 (26%) of the 86 participants developed EMTP. Nine of them developed bilateral symptoms. A total of 57 (66%) participants did not sustain any overuse injury of the lower extremity and were used as a control group. During the study follow-up, four students dropped out of the education programme, none of whom presented with EMTP. Anthropometric data on the participants are listed in table 2.
Cox regression analysis revealed several significant predictors for the development of EMTP. Especially DJS in the transverse plane (rotations around the Z-axis) seemed to be important, where ROM of hip referenced to the pelvis, pelvis referenced to the thorax and thorax referenced to the lab were found to be significant predictors for the development of EMTP. These parameters were found to be significant contributors during the two phases of the SLDJ. Descriptives and results for the Cox regression analysis are presented in table 3.
The strength of the predictive values of the significant contributors to the development of EMTP is presented in table 4.
The Cox regression analysis revealed that the hazard of developing EMTP at any time, increases with 15% if thorax ROM in the transverse plane increases with 1° during landing phase. The hazard of developing EMTP at any time, increases with 9% if transverse thorax ROM increases with 1° during push-off phase. Similarly, the hazard of developing EMTP at any time, increases with 10% if transverse pelvis-thorax ROM increases with 1° during push-off phase.
The hazard of developing EMTP at any time increases with 13% if transverse hip ROM increases with 1° during landing phase. If transverse hip ROM increases with 1° during push-off phase, the hazard of developing EMTP at any time increases with 10%.
Mean and SD values of these predictive values are shown in figure 3.
The ROC-analysis revealed a cut-off value of >12.27° for transverse thorax ROM during landing phase, >13.24° for transverse thorax ROM during push-off phase, >16.76° for transverse pelvic-thoracic ROM during push-off phase, >8.93° for transverse hip ROM during landing phase and >6.12° for transverse hip ROM during push-off phase. These cut-off values are shown in table 5.
This study is the first to prospectively identify the role of DJS parameters in the development of one of the most important overuse injuries, EMTP. More than 1/4 participants in this female population developed EMTP. This incidence (26%) is in accordance with a previous study.3
The results of this study demonstrated that increased transverse movement of the hip and the thorax during a functional single-leg task, are significant risk factors for the development of EMTP in female athletes. These accessory movements of the hip and the thorax can be seen as the result of impaired neuromuscular control and therefore impaired ability to maintain DJS in the lumbopelvic-hip region.41
As mentioned above, the literature reveals that potential contributors to LE injuries can be found distally and proximally in the kinetic chain.14 Nevertheless, comparison of this study with other studies is rather difficult, since no study prospectively examined the role of distal and proximal functional DJS factors in EMTP so far. In contrast to this study, other studies focused on peak outcome measures, rather than functional outcome measures.26 ,27 The results of this current study demonstrate that functional output measures like the ability to maintain DJS during functional activities, are indeed of great value since increased transverse ROM of hip and thorax were defined as risk factors for EMTP.
In order to interpret the results of this study, it may be interesting to describe a possible relationship between decreased ability to maintain transverse DJS of the hip and the thorax and increased lower leg strains, since these strains are described to induce EMTP.3 ,44–46 The decreased ability to maintain transverse DJS of the hip and the thorax results in unneeded and therefore accessory movements. It is shown in this study that participants with increased accessory movements around the Z-axis in the transverse plane of the hip and the thorax while executing the SLDJ, are at a risk for the development of EMTP.
These altered proximal-to-distal movement patterns may cause more eccentric activity of lower leg musculature in the attempt to control the motion and may therefore lead to excessive traction to the lower leg musculature.3 However, muscle origins do not frequently correspond to the site of symptoms in EMTP,47 so tractions to the tibia may not always be the direct result of traction of the lower leg musculature. In accordance with this finding, Stickley et al48 described the deep posterior crural fascia as a potential site of traction rather than the origins of lower leg. Furthermore, Bouche and Johnson49 described the link between lower leg muscles and fascia, in which fascial tenting with muscle tractions were demonstrated. The deep posterior crural fascia as a potential site of traction may thus be the explanation for traction conferred to the tibia.48 When each TD generates this traction on midtibial musculoskeletal structures, the musculoskeletal system may become overloaded and overuse injury of the lower leg such as EMTP may occur.3 However, further and thorough exploration of the specific link between the instability parameters identified in this study and the development of EMTP should be included in future research.
Another interesting mechanism for the pathomechanics of EMTP could possibly be found in the link between altered movement patterns and therefore altered ground reaction forces.25 As aforementioned, Lawrence et al25 showed that participants with strong hip external rotators demonstrated significantly lower vertical ground reaction forces during single-leg landing. Nevertheless, in this study no significant differences were found in vertical ground reaction force between the uninjured and the EMTP group. The results in this study are thus not speculative for peak bone rates as an important risk factor in the development of EMTP.
The results of this study contribute to the growing body of evidence that lumbopelvic-hip factors indeed play an important role in the development of EMTP.24 However, the overall screening instrument for core stability function, which can be described as motor control and muscular capacity,15 has not yet been identified. Recent study results reveal the important link between hip muscle weakness and EMTP,24 but Leetun et al15 found no link between trunk muscle strength and general lower limb injury. Therefore, the identification of the specific mechanism between decreased core stability function and the development of lower extremity injuries should be the focus of future studies.
The results in this study only revealed proximal decreased DJS parameters, whereas in literature distal parameters are described to play an important role in EMTP.3–5 Riemann et al50 described an increasing role of the proximal joint musculature as the task difficulty increases. As more demanding tasks, like jumping, increase the need for appropriate proximal joint musculature function,50 less demanding tasks like marching and jogging may be more dependent on distal joint musculature function. This important statement may indicate the need for specific screening tools based on level of activity in order to develop comprehensive preventive and diagnostic screening tools.
As a first and important limitation of this study, we note that these results concern female physical education students. Consequently, these findings cannot be generalised to a civilian setting. However, women suffer disproportionately higher rates of EMTP51 and therefore are an important population for studies on EMTP. Second, structural deformities of the lower extremity such as femoral anteversion and coxa vara, have significant effects on lower limb function.52 ,53 Nevertheless, the measurement of possible deformities was not part of this study's protocol. These parameters should be taken into account in future research, especially since they are common features of the female gender. Another limitation can be found in the difference between landing mechanics from a drop jump compared with landing from a jump, however, the practical advantages of the SLDJ (eg, standardising drop height vs jumping height) contribute to the value of this operative screening instrument. As a final but important limitation, muscle fatigue evaluation was not performed in this study. Muscle fatigue however has been described as playing an important role in the development of EMTP54 and therefore is of great interest in research concerning these lower extremity overuse injury.
The decreased ability to maintain transverse DJS of the hip and the thorax during SLDJ, was found to be a significant risk factor for the development of EMTP in female athletes. We suggest that the decreased ability to control the lower extremity movement during SLDJ resulted in increased risk for developing EMTP. Proximal stability seems to be an important factor to take into account for prevention and rehabilitation purposes.
What are the new findings
This prospective study is the first to evaluate proximal dynamic joint stability (DJS) parameters as risk factors for the development of exertional medial tibial pain (EMTP) in women.
Since lower limb and trunk movements during the single-leg drop jump (SLDJ) are located in the sagittal plane, increased range of motion in the frontal and transverse plane can be seen as accessory movements. Decreased ability to maintain DJS can lead to accessory movements.
The results of this study identified that accessory movements of the hip and thorax in the transverse plane during SLDJ are predictive parameters for development of EMTP in women.
As only proximal DJS factors were identified as significant contributors for EMTP and as an increasing role of the proximal joint musculature is needed when task difficulty increases, level of activity may be a very important factor to take into account when developing screening tools for the prevention and revalidation of EMTP.
The authors gratefully acknowledge Fabienne Van De Steene and Roel De Ridder for their clinical point of view and assistance in analysis of the data, and Dr Vanden Boscche and Dr Steyaert for their assistance in data collection of the injuries.
Contributors RV was responsible for the overall content as guarantor and was involved in the conception and design of the study, acquisition of data, analysis and interpretation of data, and writing and drafting the article or revising it critically for important intellectual content, describing clinical implications of the results, and final approval of the version to be published. DDC was involved in the conception and design of the study, acquisition of data, revising it critically for important intellectual content, and final approval of the version to be submitted. JV was involved in conception and design of the lower limb trunk model used during data collection and further analysis, conception of analysing methods concerning the biomechanical data, and revising the manuscript critically for important intellectual content. TW was involved in the conception and design of the study, acquisition of data, analysis and interpretation of data, revising it critically for important intellectual content, and final approval of the version to be published. TP was involved in acquisition of data, conception of analysing methods concerning the biomechanical data and revising the manuscript critically for important intellectual content. EW was involved in the conception and design of the study, acquisition of data, analysis and interpretation of data, describing clinical implications of the results, revising the manuscript critically for important intellectual content, and final approval of the version to be published.
Funding This research was funded by BOF-UGent 05V00910.
Competing interests None.
Patient consent Obtained.
Ethics approval The Ethical Committee of Ghent University Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.
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