Context

 People with chronic ankle instability (CAI) exhibit less weight-bearing dorsiflexion range of motion (ROM) and less knee flexion during landing than people with stable ankles. Examining the relationship between dorsiflexion ROM and landing biomechanics may identify a modifiable factor associated with altered kinematics and kinetics during landing tasks.

Objective

 To examine the relationship between weight-bearing dorsiflexion ROM and single-legged landing biomechanics in persons with CAI.

Design

 Cross-sectional study.

Setting

 Laboratory.

Patients or Other Participants

 Fifteen physically active persons with CAI (5 men, 10 women; age = 21.9 ± 2.1 years, height = 168.7 ± 9.0 cm, mass = 69.4 ± 13.3 kg) participated.

Intervention(s)

 Participants performed dorsiflexion ROM and single-legged landings from a 40-cm height. Sagittal-plane kinematics of the lower extremity and ground reaction forces (GRFs) were captured during landing.

Main Outcome Measure(s)

 Static dorsiflexion was measured using the weight-bearing–lunge test. Kinematics of the ankle, knee, and hip were observed at initial contact, maximum angle, and sagittal displacement. Sagittal displacements of the ankle, knee, and hip were summed to examine overall sagittal displacement. Kinetic variables were maximum posterior and vertical GRFs normalized to body weight. We used Pearson product moment correlations to evaluate the relationships between dorsiflexion ROM and landing biomechanics. Correlations (r) were interpreted as weak (0.00–0.40), moderate (0.41–0.69), or strong (0.70–1.00). The coefficient of determination (r2) was used to determine the amount of explained variance among variables.

Results

 Static dorsiflexion ROM was moderately correlated with maximum dorsiflexion (r = 0.49, r2 = 0.24), ankle displacement (r = 0.47, r2 = 0.22), and total displacement (r = 0.67, r2 = 0.45) during landing. Dorsiflexion ROM measured statically and during landing demonstrated moderate to strong correlations with maximum knee (r = 0.69–0.74, r2 = 0.47–0.55) and hip (r = 0.50–0.64, r2 = 0.25–0.40) flexion, hip (r = 0.53–0.55, r2 = 0.28–0.30) and knee (r = 0.53–0.70, r2 = 0.28–0.49) displacement, and vertical GRF (−0.47– −0.50, r2 = 0.22–0.25).

Conclusions

 Dorsiflexion ROM was moderately to strongly related to sagittal-plane kinematics and maximum vertical GRF during single-legged landing in persons with CAI. Persons with less dorsiflexion ROM demonstrated a more erect landing posture and greater GRF.

Key Points
  • During a single-legged landing, persons with chronic ankle instability demonstrated moderate to strong relationships between dorsiflexion range of motion (ROM) and sagittal-plane kinematics at the knee and hip and vertical ground reaction forces.

  • Persons with less dorsiflexion ROM exhibited a less flexed landing strategy that attenuated ground reaction forces less efficiently.

  • Identifying dorsiflexion deficits may enable clinicians to implement interventions to increase ROM and potentially modify the landing biomechanics that persons with chronic ankle instability exhibit.

Ankle sprains are one of the most common injuries associated with athletics.1  In addition, up to 73% of athletes who sustain ankle sprains experience recurrent ankle sprains, and 59% report functional loss and residual symptoms that have affected athletic performance.2  Residual symptoms resulting from ankle sprains are often associated with a condition known as chronic ankle instability (CAI). This condition is characterized by repetitive ankle-sprain injuries, frequent episodes of the ankle “giving way,” and decreased self-reported function stemming from an acute ankle sprain.3  Persons with CAI have reported diminished health-related quality of life and are at greater risk for developing posttraumatic ankle osteoarthritis.4,5  Based on the number of persons who develop CAI and the long-term consequences of the condition, a better understanding of the contributing factors is warranted to improve clinical intervention strategies.

Chronic ankle instability may be associated with several mechanical impairments in ankle function,3 including a deficit in ankle-joint dorsiflexion range of motion (ROM).3,6  Whereas the exact prevalence of dorsiflexion ROM deficits has not been determined, 30% to 74% of persons with CAI have at least a 5° deficit in weight-bearing dorsiflexion ROM compared with the contralateral limb.7,8  The exact origin of dorsiflexion ROM deficits is unclear, but it likely results from arthrokinematic alterations and adaptive shortening of the triceps surae muscle group.9,10  More importantly, dorsiflexion deficits may limit the ability to fully achieve a closed-packed, stable position of the ankle during dynamic activities, such as gait and landing, which may promote the pathomechanics associated with ankle-sprain mechanisms.9,11,12  Therefore, a cascade of structural impairments leading to decreased dorsiflexion ROM may affect the ability to execute functional activities and ultimately contribute to the repeated ankle sprains and episodes of giving way related to CAI.

Dorsiflexion ROM plays a prominent role in the biomechanics of tasks that require landing.13  Greater passive open chain dorsiflexion ROM has been associated with greater hip and knee flexion and lower ground reaction forces (GRFs) during a jump-landing task in healthy persons.13  Those with greater dorsiflexion ROM land with a less erect posture by using greater sagittal-plane displacement, which allows the body to attenuate forces more efficiently.13  Therefore, the available amount of dorsiflexion ROM may influence function not only at the ankle but also at more proximal structures in the lower extremity. Persons with CAI have demonstrated less dorsiflexion ROM during gait11,14  and less knee flexion during landing than persons without CAI, but these findings have not been consistent in the literature.15,16  Furthermore, persons with CAI have shown greater energy dissipation at the ankle and less energy dissipation at the knee.17  Cumulatively, these observations suggest that alterations exist in the distal to proximal linkage of the kinetic chain of the lower extremity in persons with CAI.17  Further examining a potential connection between dorsiflexion ROM and landing biomechanics may provide additional insight into these findings.

Persons who have CAI and less dorsiflexion ROM may also exhibit more erect landing postures and greater GRF, which may have implications for sustaining future lower extremity injuries or episodes of giving way.18,19  Examining this relationship may further support integrating clinical intervention strategies that target dorsiflexion ROM into the rehabilitation of persons with CAI.9  Therefore, the purpose of our study was to examine the relationship between dorsiflexion ROM and single-legged landing biomechanics in persons with CAI. We examined dorsiflexion ROM statically, using the weight-bearing–lunge test, and dynamically, using motion capture, to determine its relationship to landing biomechanics. In addition, we focused on the sagittal-plane kinematics of the lower extremity and GRFs to explore how dorsiflexion ROM may influence force attenuation in persons with CAI. Kinematics were examined in the sagittal plane because it is primarily responsible for force attenuation during landing tasks.20  We hypothesized that persons with less dorsiflexion ROM would exhibit less sagittal-plane motion throughout the lower extremity and greater GRF during a single-legged drop-landing task.

METHODS

Design

With this cross-sectional study, we evaluated the relationship between dorsiflexion ROM and single-legged drop-landing biomechanics in persons with CAI. The dependent variables were weight-bearing dorsiflexion ROM and sagittal-plane kinematics at the ankle, knee, and hip, as well as GRF, recorded during single-legged drop landings.

Participants

Fifteen physically active persons with CAI (5 men, 10 women; age = 21.9 ± 2.1 years, height = 168.7 ± 9.0 cm, mass = 69.4 ± 13.3 kg) were recruited from a large public university over the course of 6 months to participate in this study. The inclusion criteria were consistent with the International Ankle Consortium's position statement on selection criteria for patients with CAI.21  Specifically, participants had to report a history of at least 1 substantial ankle sprain and at least 1 episode of giving way in the 3 months before the study (ankle sprains = 2.7 ± 2.4, time since last sprain = 25.2 ± 25.2 months, incidences of giving way in the 3 months before the study = 4.9 ± 5.5). Ankle sprain was defined as an incident in which the rearfoot was inverted or supinated and resulted in a combination of swelling, pain, and time missed or modification of normal function for at least 1 day. An episode of giving way was described as an incident in which the rearfoot suddenly rolled, felt weak, or lost stability; however, the person could continue with normal function. Participants also had to give an affirmative answer to at least 4 items on the Ankle Instability Instrument22  (6.3 ± 1.5) and report at least moderate levels of physical activity on the NASA Physical Activity Scale23  (6.1 ± 1.8). To further describe the level of activity limitation and participation restriction, each participant completed the Foot and Ankle Ability Measure (FAAM) Activities of Daily Living (90.6% ± 5.4%) and FAAM Sport (79.0% ± 12.5%) instruments.24  To supplement FAAM scores, participants completed a global rating of function scale at the end of each FAAM subscale; function was rated from 0% to 100%, with 100% representing the level of function before injury (FAAM Activities of Daily Living = 89.4% ± 8.3%, FAAM Sport = 81.6% ± 12.7%). Participants were excluded if they had experienced an ankle sprain in the 6 weeks before the study, had a history of lower extremity fracture or surgery, had sustained any other lower extremity injury in the 6 months before the study, or reported any other conditions that might affect landing. If a participant reported bilateral ankle instability, the limb with the lower FAAM scores was used for testing. All participants provided written informed consent, and the study was approved by the Institutional Review Board of Old Dominion University.

Instrumentation

An 8-camera motion analysis system (model MX40; Vicon Motion Systems, Denver, CO) collected kinematic data at 200 Hz. Three-dimensional force data were collected at 1000 Hz using a force plate (model 4060-10; Bertec Corp, Columbus, OH).

Procedures

Participants reported to the laboratory for a single testing session lasting approximately 1.5 hours. They performed a weight-bearing–lunge test (WBLT) and a single-legged drop-landing task on the involved limb. All measures were taken by the same investigator (S.L.G.). After completing the WBLT, participants were outfitted with retroreflective markers for tracking motion during the drop-landing task. To accurately capture motion-analysis data, we required all participants to wear spandex shorts and low-cut socks, men to wear no shirts, and women to wear sports bras. Participants also wore Nike sneakers (Air Max Glide; Nike, Beaverton, OR) provided by the investigators to eliminate variables introduced by various shoe types or brands. Participants selected their shoe size in men's or women's sizes.

Maximum weight-bearing ankle dorsiflexion ROM was assessed statically using the WBLT as described by Hoch and McKeon.25  To perform the WBLT, the participant was positioned facing a wall with the involved foot in front, parallel with a tape measure secured to the floor, and the great toe touching the wall while the uninvolved foot was placed comfortably behind the involved foot. The WBLT uses a knee-to-wall principle that requires the participant to perform a lunge in which the knee flexes to a point where the anterior knee makes contact with the wall while the test heel remains firmly planted on the floor. Participants initially were progressed backward in 1-cm increments until heel or knee contact could no longer be maintained during the lunge. Subsequent changes in distance from the wall were made in smaller increments until the maximum lunge distance was identified. Maximum lunge distance was measured from the tip of the great toe to the wall to the nearest 0.1 cm.25  Maximum dorsiflexion ROM was assessed 3 times for each participant and averaged for analysis. The WBLT has demonstrated strong intratester and intertester reliability (intraclass correlation coefficient > 0.90).26,27  We selected this method of assessing maximum dorsiflexion ROM over traditional open chain goniometric techniques because it has been correlated with functional activities and has identified dorsiflexion deficits in persons with CAI.6 

Upon completion of the WBLT, we prepared participants for motion capture by applying retroreflective markers bilaterally28  over the following locations using double-sided tape for standing calibration: acromioclavicular joint, anterior-superior iliac spine, posterior-superior iliac spine, iliac crest, greater trochanter, lateral and medial femoral condyles, lateral and medial malleoli, base of the fifth metatarsal, and base of the first metatarsophalangeal joint. Cluster plates comprising 4 markers on semirigid, molded Orthoplast (Johnson & Johnson, New Brunswick, NJ) were attached by hook-and-loop fasteners at the heel of the shoe and on foam wraps snugly fit around the lower leg, thigh, and midthoracic region on the back. Participants were instructed to stand on the force plate and raise their upper extremities for calibration. Once calibration was completed, all markers except those on the anterior-superior iliac spine and posterior-superior iliac spine and cluster plates were removed for dynamic motion capture.

To perform the drop-landing task, participants stood on a 40-cm box with the uninvolved limb and were instructed to drop on the involved limb onto the force plate located 10 cm in front of the box.29  They performed 3 to 5 practice trials until they were comfortable with the drop-landing task. We also informed participants that a successful landing trial required them to drop down on the force plate without propelling forward, avoid contact with the ground on the uninvolved foot, maintain the upper extremities folded across the chest, land with the entire foot on the force plate, and avoid any subsequent hops or sliding of the foot. This position had to be maintained long enough for full weight acceptance to occur on the single limb. Data were captured from the initiation of the drop until the participant had successfully completed the landing for further data reduction and analysis. Trials deemed unsuccessful were discarded and repeated until 5 successful trials were captured and subsequently used for data analysis.

Data Reduction

Data were postprocessed through Vicon Nexus software (version 1.8.5; Vicon Motion Systems) to identify and fill any missing trajectories less than 10 frames. These gaps were pattern filled using a marker collocated on the same cluster. Data were transferred to Visual 3D (version 5.0; C-Motion, Inc, Rockville, MD) to reconstruct the model and calculate both kinematic and kinetic variables from marker and force-plate data. Raw 3-dimensional marker coordinate and GRF data were low-pass filtered using a fourth-order, zero-lag, recursive Butterworth filter with cutoff frequencies of 12 Hz and 50 Hz, respectively.30  A kinematic model comprising 8 skeletal segments (trunk; pelvis; and bilateral thighs, shanks, and feet) was created from the standing calibration trial.28,31  Hip-joint center was defined as 25% of the distance from the ipsilateral to the contralateral greater trochanter marker,32  knee-joint center was defined as the midpoint between the lateral and medial markers on the condyles of the femur,33  and ankle-joint center was defined as the midpoint between the medial and lateral malleoli markers.34  Three-dimensional ankle, knee, and hip angles were calculated using a joint coordinate system approach.33,34  Initial contact was identified as the point in the trial when the vertical GRF exceeded 10 N, and the end of the landing phase was defined as maximum knee flexion.28  Kinematics for the ankle, knee, and hip were observed at initial contact, maximum angle, and total displacement in the sagittal plane. Total displacement of the ankle, knee, and hip was defined as the final angular position of the joint minus the initial angular position of the joint. We also summed the sagittal-plane displacements observed at the ankle, knee, and hip to examine overall sagittal-plane displacement. Kinetic variables were maximum posterior and vertical GRFs, which were normalized to body weight. Posterior GRF was included because this measure was associated with dorsiflexion ROM in a previous study13  and is often examined when investigating lower extremity injury.35,36  The average of 5 successful trials was used to create each variable and entered into analyses.

Statistical Analysis

We calculated descriptive statistics, including means and standard deviations, for all dependent variables. Pearson product moment correlations were conducted to evaluate (1) the relationship between maximum dorsiflexion on the WBLT and the kinematic and kinetic variables associated with the drop-landing task and (2) the relationship between maximum dorsiflexion angle during the drop-landing task and the hip kinematics, knee kinematics, and kinetic variables associated with the drop-landing task. Pearson product moment correlation coefficients (r) were interpreted as weak (0.00–0.40), moderate (0.41–0.69), or strong (0.70–1.00).37  We also calculated the coefficient of determination (r2) to examine the explained variance exhibited for each analysis.

RESULTS

Descriptive statistics for all dependent variables are presented in Table 1. Dorsiflexion ROM on the WBLT was positively, moderately correlated with maximum ankle dorsiflexion, knee and hip flexion, ankle and hip displacement, overall sagittal-plane displacement, and vertical GRF and was positively, strongly correlated with knee displacement. All other relationships were considered weak. Pearson product moment correlation coefficients, coefficients of determination, and probability statistics between maximum weight-bearing dorsiflexion ROM and all kinematic and kinetic variables are presented in Table 2.

Table 1.

Dependent Variable Descriptive Statisticsa

Dependent Variable Descriptive Statisticsa
Dependent Variable Descriptive Statisticsa
Table 2.

Correlations Between Maximum Weight-Bearing Dorsiflexion Range of Motion and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces

Correlations Between Maximum Weight-Bearing Dorsiflexion Range of Motion and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces
Correlations Between Maximum Weight-Bearing Dorsiflexion Range of Motion and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces

Maximum dorsiflexion angle during the drop-landing task was positively, moderately correlated with maximum hip flexion, knee and hip displacement, and vertical GRF and was positively, strongly correlated to knee flexion at initial contact and maximum knee flexion. All other relationships were considered weak. Pearson product moment correlation coefficients, coefficients of determination, and probability statistics between maximum dorsiflexion angle during the drop-landing task and all other kinematic and kinetic variables are presented in Table 3.

Table 3.

Correlations Between Maximum Dorsiflexion Angle and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces

Correlations Between Maximum Dorsiflexion Angle and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces
Correlations Between Maximum Dorsiflexion Angle and Lower Extremity Kinematics and Normalized Maximum Ground Reaction Forces

DISCUSSION

The main finding of our study was that weight-bearing dorsiflexion ROM measured statically using the WBLT and dynamically during the drop-landing task was moderately to strongly associated with sagittal-plane kinematics throughout the lower extremity and vertical GRF during a single-legged drop-landing task in persons with CAI. These observations indicated that persons with less dorsiflexion ROM exhibited more erect postures during the drop-landing task. Overall, dorsiflexion ROM seemed to have a lesser influence on kinematics at initial contact and a greater association with maximum angles and displacements. This observation suggests that the available weight-bearing dorsiflexion ROM may have a greater effect on landing biomechanics as the lower extremity attempts to attenuate forces during the later stages of landing in persons with CAI.

Our observations are supported by those of previous researchers who examined the relationship between passive open chain measures of dorsiflexion ROM and single-legged jump-landing kinematics in healthy adults.13  Fong et al13  reported that greater extended-knee dorsiflexion ROM was associated with greater knee (r2 = 0.21) and hip (r2 = 0.13) displacement during jump landing in healthy persons, and we determined that the WBLT and maximum dorsiflexion angle were also associated with greater knee (r2 = 0.28–0.49) and hip (r2 = 0.28–0.30) displacement during a drop-landing task in persons with CAI. Whereas the results of Fong et al13  support our observations, several methodologic differences should be considered when making comparisons. Fong et al13  used traditional open chain measures of dorsiflexion ROM with a long-arm goniometer, and we used the WBLT and motion capture to measure weight-bearing dorsiflexion ROM. In addition, Fong et al13  incorporated a jumping component into the landing task, and we instructed participants to perform a drop landing with no jumping component. Regardless of the methodologic differences, we and Fong et al13  determined that clinical assessments of dorsiflexion ROM are related to landing biomechanics. This observation suggests that dorsiflexion ROM may have a meaningful influence on lower extremity kinematics regardless of CAI status.

We determined that dorsiflexion ROM measured on the WBLT explained more than 20% of the variance in maximum dorsiflexion and ankle displacement. In contrast to these results, Fong et al13  reported a weak correlation, which explained only 2% of the variance between dorsiflexion ROM and ankle displacement in healthy adults. This discrepancy may in part be related to the amount of variability in the ankle angle at initial contact. We observed a wide ROM at initial contact (standard deviation = 7.70°, range = 28.87°), but Fong et al13  reported nearly double the variability (standard deviation = 15°, range = 60°). It is unclear whether these differences are methodologic in nature, but this narrower range of variability may be an aspect of landing biomechanics that warrants further investigation in persons with CAI. Whereas the implications for less variability in dorsiflexion angle at initial contact are unclear, Terada et al17  determined that persons with CAI demonstrated greater energy dissipation at the ankle, which may be due to ankle stiffness during landing. Researchers should continue to examine ankle sagittal-plane motion in persons with CAI and determine if this motion contributes to reinjury mechanisms.

We hypothesized that persons with less dorsiflexion ROM would exhibit greater GRF. Dorsiflexion ROM explained 22% to 25% of the variance in vertical GRF, which is consistent with the results of Fong et al,13  who determined that extended-knee dorsiflexion ROM explained 17% of the variance in healthy adults. However, our results explained very little variance (<1%) in posterior GRF, which contradicts the 9% of explained variance reported in healthy participants.13  Secondary analyses from our data indicated that maximum hip and knee flexion, hip and knee displacement, and overall displacement explained large proportions of the variance (r2 = 0.29–0.52) associated with vertical GRF, indicating that more erect postures resulted in greater vertical GRF. Therefore, static or dynamic weight-bearing dorsiflexion values may provide information that could aid in identifying persons who are more likely to land with less sagittal-plane displacement and subsequently higher vertical GRF. In future studies with larger sample sizes, researchers should consider examining how lower extremity kinematics and dorsiflexion ROM may interact to predict the absorption of vertical GRF during landing. This research may provide future directions for examining not only the pathomechanics associated with CAI but also lower extremity injury mechanisms in general.

Overall, static and dynamic measures of weight-bearing dorsiflexion ROM demonstrated relationships similar to the kinematics of more proximal joints and GRFs. Both measures demonstrated moderate to strong correlations with maximum knee and hip angle, knee and hip displacement, and vertical GRF. The most distinctive difference was the strong relationship exhibited between maximum ankle-dorsiflexion angle during landing and knee-flexion angle at initial contact, which may be related to the direct linkage between these joints during landing. The similar pattern of correlation demonstrated by the static and dynamic measures of weight-bearing dorsiflexion indicated that the less instrumented static measure may be suitable for future studies in which researchers are interested in identifying persons who land with more erect postures and greater vertical GRF. Whereas the value of this measure certainly needs to be confirmed with additional systematic investigation, it could be very beneficial, as the WBLT provides a more feasible approach to clinically implementing maximum dorsiflexion ROM measures into injury evaluation and prevention.

Persons with CAI demonstrated correlations between dorsiflexion ROM and landing biomechanics that were similar to what has been reported in healthy persons.13  This observation is encouraging because it suggests that persons with CAI, who commonly exhibit dorsiflexion deficits,3,6  may fall along the same continuum of function regarding the relationships that we examined. Therefore, when efforts are made to increase dorsiflexion ROM in persons with deficits, a reciprocating improvement in landing biomechanics may also be anticipated. This concept is supported by DiStefano et al,38  who determined that limiting ankle sagittal-plane ROM with an ankle brace resulted in immediate decreases in ankle and knee sagittal-plane ROM during landing. In addition, the presence of a dorsiflexion ROM deficit is accompanied by decreased self-reported function associated with activities of daily living and sport-related activities in persons with CAI39  and patients who have sustained acute ankle sprains.40  Therefore, when dorsiflexion deficits are present, alterations in lower extremity function may follow. The similarities between our study and the study of Fong et al13  are also important because they indicate that the influence of dorsiflexion ROM on landing biomechanics may transcend specific clinical populations and have implications for lower extremity injury mechanisms in general. Studies in which investigators directly compare persons with CAI and healthy persons and studies in which investigators seek to increase dorsiflexion ROM and examine landing biomechanics are logical next steps to advance this theory and this line of inquiry.

Our study provided insight into possible contributing factors to CAI from not only a biomechanical or disease-oriented perspective but also a patient-oriented perspective. Based on the results of the FAAM Sport, most participants reported functional deficits associated with sport activities. Closer examination of the individual FAAM Sport items determined that 13 of the 15 participants reported at least slight difficulty with landing activities and 1 of the participants who did not report difficulty had the greatest dorsiflexion ROM (14 cm). Researchers targeting dorsiflexion ROM and landing biomechanics using clinical interventions should examine treatment effects from disease-oriented and patient-oriented perspectives. This work may provide complementary data that can be used more readily in clinical settings for patient evaluation and goal setting.

Finally, our results support incorporating interventions that target dorsiflexion ROM into the rehabilitation strategy for persons with CAI and potentially persons with dorsiflexion deficits in general. More specifically, improving dorsiflexion ROM by increasing the extensibility of capsular tissues or the flexibility of the triceps surae muscle group through manual therapies or stretching techniques may enhance landing biomechanics by reducing erect postures. This is important for persons with CAI, as increased plantar flexion at the ankle during landing from a jump has been identified as a risk factor for ankle sprain, particularly in persons with a history of sprain.41  Recent evidence42  has indicated that persons with CAI can achieve more dorsiflexed positions at the point of initial contact during a jump-landing task immediately after a single session of joint mobilization focused on improving dorsiflexion ROM. Delahunt et al42  did not report hip or knee kinematics, GRFs, or how long the effects of manual therapy treatments may last but did provide preliminary evidence that sagittal-plane kinematics could be influenced by readily available clinical interventions for increasing dorsiflexion ROM. In addition, after 2 weeks of talocrural- joint mobilization, persons with CAI reported an improvement in self-reported landing ability and concurrent increases in dorsiflexion ROM.43,44  This observation supports the importance of examining changes in function with a combination of patient-, clinician-, and laboratory-oriented measures. Other interventions and the long-term effects of treatment should be investigated more.

Our study had limitations. We used a 40-cm box for the drop landings to create a standard height for all participants. This box height may be more or less difficult for participants depending on height, lower extremity length, or jumping capability. Researchers may consider normalizing drop height by making the box height a percentage of the participant's height or maximum vertical-jump height to have a more consistent level of difficulty across participants. The kinematics exhibited during drop landing were similar to those reported in previous studies in some respects but very different in others. For example, the ankle kinematics demonstrated in our study were similar to those in previous studies12,42,45 ; however, Caulfield and Garrett16  reported considerably greater dorsiflexion values. Similar differences were noted with knee kinematics, as considerable variations are present in knee-flexion and knee-displacement values during landing in persons with CAI across the literature.15,16,45  Kinematic variations may be due to differences in landing tasks, collection methods, or participant inclusion criteria. In addition, our retrospective study could not generate any cause-and-effect conclusions regarding dorsiflexion, landing biomechanics, and the progression of CAI. Whereas the WBLT has demonstrated good reliability,27  we did not establish the reliability of the investigator in our study. We also did not conduct an a priori power analysis. However, post hoc power analyses indicated that the relationships, which were moderate to strong, had powers of 0.35 to 0.96 at an α level of .05. Finally, we focused only on kinematics in the sagittal plane and GRFs during drop landing in persons with CAI. Future researchers may consider providing a more comprehensive examination of kinematics and joint moments to determine if dorsiflexion ROM is related to alterations in other planes of movement or the forces experienced at individual joints in participants with CAI and healthy control participants.

CONCLUSIONS

Persons with CAI exhibited moderate to strong relationships between weight-bearing dorsiflexion ROM and sagittal-plane kinematics at the knee and hip and vertical GRF during a single-legged drop landing. Persons with less dorsiflexion ROM demonstrated a less flexed landing strategy that was less efficient at attenuating GRF. Identifying dorsiflexion deficits in persons with CAI may allow clinicians to implement interventions to increase ROM and potentially modify the landing biomechanics that these persons exhibit.

REFERENCES

1
Hootman
JM
,
Dick
R
,
Agel
J.
Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives
.
J Athl Train
.
2007
;
42
(
2
):
311
319
.
2
Yeung
MS
,
Chan
KM
,
So
CH
,
Yuan
WY.
An epidemiological survey on ankle sprain
.
Br J Sports Med
.
1994
;
28
(
2
):
112
116
.
3
Hertel
J.
Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability
.
J Athl Train
.
2002
;
37
(
4
):
364
375
.
4
Arnold
BL
,
Wright
CJ
,
Ross
SE.
Functional ankle instability and health-related quality of life
.
J Athl Train
.
2011
;
46
(
6
):
634
641
.
5
Valderrabano
V
,
Hintermann
B
,
Horisberger
M
,
Fung
TS.
Ligamentous posttraumatic ankle osteoarthritis
.
Am J Sports Med
.
2006
;
34
(
4
):
612
620
.
6
Hoch
MC
,
Staton
GS
,
Medina McKeon
JM
,
Mattacola
CG
,
McKeon
PO.
Dorsiflexion and dynamic postural control deficits are present in those with chronic ankle instability
.
J Sci Med Sport
.
2012
;
15
(
6
):
574
579
.
7
Beazell
JR
,
Grindstaff
TL
,
Sauer
LD
,
Magrum
EM
,
Ingersoll
CD
,
Hertel
J.
Effects of a proximal or distal tibiofibular joint manipulation on ankle range of motion and functional outcomes in individuals with chronic ankle instability
.
J Orthop Sports Phys Ther
.
2012
;
42
(
2
):
125
134
.
8
Wheeler
TJ
,
Basnett
CR
,
Hanish
MJ
,
et al
.
Fibular taping does not influence ankle dorsiflexion range of motion or balance measures in individuals with chronic ankle instability
.
J Sci Med Sport
.
2013
;
16
(
6
):
488
492
.
9
Hoch
MC
,
Grindstaff
TL.
Effectiveness of joint mobilization in patients with chronic ankle instability: a review of the literature
.
Athl Train Sports Health Care
.
2012
;
4
(
5
):
237
244
.
10
Wikstrom
EA
,
Hubbard
TJ.
Talar positional fault in persons with chronic ankle instability
.
Arch Phys Med Rehabil
.
2010
;
91
(
8
):
1267
1271
.
11
Drewes
LK
,
McKeon
PO
,
Kerrigan
DC
,
Hertel
J.
Dorsiflexion deficit during jogging with chronic ankle instability
.
J Sci Med Sport
.
2009
;
12
(
6
):
685
687
.
12
Delahunt
E
,
Monaghan
K
,
Caulfield
B.
Changes in lower limb kinematics, kinetics, and muscle activity in subjects with functional instability of the ankle joint during a single leg drop jump
.
J Orthop Res
.
2006
;
24
(
10
):
1991
2000
.
13
Fong
CM
,
Blackburn
JT
,
Norcross
MF
,
McGrath
M
,
Padua
DA.
Ankle-dorsiflexion range of motion and landing biomechanics
.
J Athl Train
.
2011
;
46
(
1
):
5
10
.
14
Brown
C.
Foot clearance in walking and running in individuals with ankle instability
.
Am J Sports Med
.
2011
;
39
(
8
):
1769
1776
.
15
Gribble
PA
,
Robinson
RH.
Alterations in knee kinematics and dynamic stability associated with chronic ankle instability
.
J Athl Train
.
2009
;
44
(
4
):
350
355
.
16
Caulfield
B
,
Garrett
M.
Functional instability of the ankle: differences in patterns of ankle and knee movement prior to and post landing in a single leg jump
.
Int J Sports Med
.
2002
;
23
(
1
):
64
68
.
17
Terada
M
,
Pfile
KR
,
Pietrosimone
BG
,
Gribble
PA.
Effect of chronic ankle instability on energy dissipation in the lower extremity
.
Med Sci Sports Exerc
.
2013
;
45
(
11
):
2120
2128
.
18
Hadzic
V
,
Sattler
T
,
Topole
E
,
Jarnovic
Z
,
Burger
H
,
Dervisevic
E.
Risk factors for ankle sprain in volleyball players: a preliminary analysis
.
Isokinet Exerc Sci
.
2009
;
17
(
3
):
155
160
.
19
Aerts
I
,
Cumps
E
,
Verhagen
E
,
Verschueren
J
,
Meeusen
R.
A systematic review of different jump-landing variables in relation to injuries
.
J Sports Med Phys Fitness
.
2013
;
53
(
5
):
509
519
.
20
Devita
P
,
Skelly
WA.
Effect of landing stiffness on joint kinetics and energetics in the lower extremity
.
Med Sci Sports Exerc
.
1992
;
24
(
1
):
108
115
.
21
Gribble
PA
,
Delahunt
E
,
Bleakley
CM
,
et al
.
Selection criteria for patients with chronic ankle instability in controlled research: a position statement of the International Ankle Consortium
.
J Athl Train
.
2014
;
49
(
1
):
121
127
.
22
Docherty
CL
,
Gansneder
BM
,
Arnold
BL
,
Hurwitz
SR.
Development and reliability of the Ankle Instability Instrument
.
J Athl Train
.
2006
;
41
(
2
):
154
158
.
23
Wier
LT
,
Ayers
GW
,
Jackson
AS
,
Rossum
AC
,
Poston
WS
,
Foreyt
JP.
Determining the amount of physical activity needed for long-term weight control
.
Int J Obes Relat Metab Disord
.
2001
;
25
(
5
):
613
621
.
24
Martin
RL
,
Irrgang
JJ
,
Burdett
RG
,
Conti
SF
,
Van Swearingen
JM.
Evidence of validity for the Foot and Ankle Ability Measure (FAAM)
.
Foot Ankle Int
.
2005
;
26
(
11
):
968
983
.
25
Hoch
MC
,
McKeon
PO.
Joint mobilization improves spatiotemporal postural control and range of motion in those with chronic ankle instability
.
J Orthop Res
.
2011
;
29
(
3
):
326
332
.
26
Bennell
K
,
Talbot
R
,
Wajswelner
H
,
Techovanich
W
,
Kelly
D
,
Hall A.
Intra-rater
and inter-rater reliability of a weight-bearing lunge measure of ankle dorsiflexion
.
Aust J Physiother
.
1998
;
44
(
3
):
175
180
.
27
Konor
MM
,
Morton
S
,
Eckerson
JM
,
Grindstaff
TL.
Reliability of three measures of ankle dorsiflexion range of motion
.
Int J Sports Phys Ther
.
2012
;
7
(
3
):
279
287
.
28
Weinhandl
JT
,
Joshi
M
,
O'Connor
KM.
Gender comparisons between unilateral and bilateral landings
.
J Appl Biomech
.
2010
;
26
(
4
):
444
453
.
29
Weinhandl
JT
,
Smith
JD
,
Dugan
EL.
The effects of repetitive drop jumps on impact phase joint kinematics and kinetics
.
J Appl Biomech
.
2011
;
27
(
2
):
108
115
.
30
Roewer
BD
,
Ford
KR
,
Myer
GD
,
Hewett
TE.
The ‘impact' of force filtering cut-off frequency on the peak knee abduction moment during landing: artefact or ‘artifiction'?
Br J Sports Med
.
2014
;
48
(
6
):
464
468
.
31
Weinhandl
JT
,
Earl-Boehm
JE
,
Ebersole
KT
,
Huddleston
WE
,
Armstrong
BS
,
O'Connor
KM.
Anticipatory effects on anterior cruciate ligament loading during sidestep cutting
.
Clin Biomech (Bristol, Avon)
.
2013
;
28
(
6
):
655
663
.
32
Weinhandl
JT
,
O'Connor
KM.
Assessment of a greater trochanter-based method of locating the hip joint center
.
J Biomech
.
2010
;
43
(
13
):
2633
2636
.
33
Grood
ES
,
Suntay
WJ.
A joint coordinate system for the clinical description of three-dimensional motions: application to the knee
.
J Biomech Eng
.
1983
;
105
(
2
):
136
144
.
34
Wu
G
,
Siegler
S
,
Allard
P
,
et al
.
ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion: part I. Ankle, hip, and spine
.
International Society of Biomechanics. J Biomech.
2002
;
35
(
4
):
543
548
.
35
Norcross
MF
,
Lewek
MD
,
Padua
DA
,
Shultz
SJ
,
Weinhold
PS
,
Blackburn
JT.
Lower extremity energy absorption and biomechanics during landing: part I. Sagittal-plane energy absorption analyses
.
J Athl Train
.
2013
;
48
(
6
):
748
756
.
36
Norcross
MF
,
Lewek
MD
,
Padua
DA
,
Shultz
SJ
,
Weinhold
PS
,
Blackburn
JT.
Lower extremity energy absorption and biomechanics during landing: part II. Frontal-plane energy analyses and interplanar relationships
.
J Athl Train
.
2013
;
48
(
6
):
757
763
.
37
Lomax
RG.
Statistical Concepts: A Second Course for Education and the Behavioral Sciences
.
Mahwah, NJ
:
L. Erlbaum Associates;
1998
:
321
325
.
38
DiStefano
LJ
,
Padua
DA
,
Brown
CN
,
Guskiewicz
KM.
Lower extremity kinematics and ground reaction forces after prophylactic lace-up ankle bracing
.
J Athl Train
.
2008
;
43
(
3
):
234
241
.
39
McKeon
PO
,
Wikstrom
EA.
Weight-bearing dorsiflexion restrictions are present on the self-reported worse limb in those with chronic ankle instability [abstract]
.
J Athl Train
.
2013
;
48
(
suppl 3
):
S207
S208
.
40
Hafner
R
,
McLeod
MM
,
Gribble
PA
,
Pietrosimone
BG.
Ankle dorsiflexion predicts self-reported disability in patients with acute ankle sprains [abstract]
.
J Athl Train
.
2012
;
47
(
suppl 3
):
S34
.
41
Wright
IC
,
Neptune
RR
,
van den Bogert
AJ
,
Nigg
BM.
The influence of foot positioning on ankle sprains
.
J Biomech
.
2000
;
33
(
5
):
513
519
.
42
Delahunt
E
,
Cusack
K
,
Wilson
L
,
Doherty
C.
Joint mobilization acutely improves landing kinematics in chronic ankle instability
.
Med Sci Sports Exerc
.
2013
;
45
(
3
):
514
519
.
43
Houston
MN
,
McKeon
PO
,
Hoch
MC.
Foot and Ankle Ability Measure scores in patients with chronic ankle instability following joint mobilization
.
Int J Athl Ther Train
.
2013
;
18
(
2
):
4
7
.
44
Hoch
MC
,
Andreatta
RD
,
Mullineaux
DR
,
et al
.
Two-week joint mobilization intervention improves self-reported function, range of motion, and dynamic balance in those with chronic ankle instability
.
J Orthop Res
.
2012
;
30
(
11
):
1798
1804
.
45
Brown
C
,
Padua
D
,
Marshall
SW
,
Guskiewicz
K.
Individuals with mechanical ankle instability exhibit different motion patterns than those with functional ankle instability and ankle sprain copers
.
Clin Biomech (Bristol, Avon)
.
2008
;
23
(
6
):
822
831
.