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Joaquin Barrios and John Willson

Medial tibiofemoral joint contact forces can be estimated using musculoskeletal models. To assess change in these forces that accompany load-modifying interventions, minimum detectable change (MDC) thresholds must be established. The primary study purpose was to derive MDCs for medial tibiofemoral peak force and force impulse during walking. The secondary purpose was to identify the proportions of individuals exhibiting reductions greater than these MDCs when walking with lateral foot wedging. Eight healthy individuals provided 3-dimensional gait data over 3 test sessions to serve as inputs for an inverse dynamics-driven medial tibiofemoral contact force model, from which MDCs for peak force and impulse were derived. The MDC was 0.246 BW (8.7%) for peak force and 0.0385 BW∙s (3.7%) for impulse. Then, 25 healthy individuals provided gait data by walking with and without 6° laterally wedged foot orthoses, and the proportion of individuals exhibiting changes in medial tibiofemoral contact peak force and impulse values exceeding the MDC threshold was determined. For impulse and peak force, 52% and 4% of participants exhibited a decrease exceeding the MDC, respectively. In summary, medial tibiofemoral contact force MDCs were derived, with impulse showing greater sensitivity than peak force to the effects of a biomechanical intervention.

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John D. Willson and Irene S. Davis

Context:

Lower extremity (LE) weakness might be associated with altered mechanics during weight bearing in subjects with patellofemoral pain syndrome (PFPS).

Objective:

To analyze LE strength, mechanics, and the association between these variables among women with and without PFPS during a simulated athletic task.

Design:

Case control.

Setting:

Motion-analysis laboratory.

Subjects:

20 women with PFPS and 20 healthy women.

Main Outcome Measures:

Peak isometric lateral trunk-flexion, hip-abduction, hip external-rotation, knee-flexion, and knee-extension strength, as well as hip- and knee-joint excursions and angular impulses during single-leg jumps.

Results:

PFPS subjects produced less hip-abduction, hip external-rotation, and trunk lateral-flexion force than the control group. The PFPS group also demonstrated greater hip-adduction excursion and hip-abduction impulses. The association between the strength measurements and LE mechanics was low.

Conclusions:

Women with PFPS demonstrate specific weaknesses and altered LE mechanics. Weakness is not, however, highly correlated with observed differences in mechanics.

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David Werner, John Willson, Richard Willy and Joaquin Barrios

Frontal plane knee alignment can influence the development and management of various knee pathologies. Valid and reliable clinical methods for assessment are needed. The primary purposes of this study were to assess the validity and reliability of inclinometer-based frontal plane tibial orientation as a limb alignment measure, and secondarily to establish normal values in healthy individuals. Frontal tibial orientation was validated per moderately strong correlation to radiographic knee alignment. Intra- and interrater reliability were excellent. The normative mean was approximately 7°. In summary, inclinometer-based frontal tibial orientation is a valid and reliable clinical measure of frontal plane knee alignment.

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Daniel J. Petit, John D. Willson and Joaquin A. Barrios

Efforts to compare different surface marker configurations in 3-dimensional motion analysis are warranted as more complex and custom marker sets become more common. At the knee, different markers can been used to represent the proximal shank. Often, two anatomical markers are placed over the femoral condyles, with their midpoint defining both the distal thigh and proximal shank segment ends. However, two additional markers placed over the tibial plateaus have been used to define the proximal shank end. For this experiment, simultaneous data for both proximal shank configurations were independently collected at two separate laboratories by different investigators, with one laboratory capturing a walking population and the other a running population. Common discrete knee joint variables were then compared between marker sets in each population. Using the augmented marker set, peak knee flexion after weight acceptance was less (1.2−1.7°, P < .02) and peak knee adduction was greater (0.7−1.4°, P < .001) in both data sets. Similarly, the calculated peak knee flexion moment was less by 15–20% and internal rotation moment was greater by 11–18% (P < .001). These results suggest that the calculation of knee joint mechanics are influenced by the proximal shank’s segment endpoint definition, independent of dynamic task, investigator, laboratory environment, and population in this study.

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Bryan Sorenson, Thomas W. Kernozek, John David Willson, Robert Ragan and Jordan Hove

Context:

Hip- and knee-joint kinematics during drop landings are relevant to lower-extremity injury mechanisms. In clinical research the “gold standard” for joint kinematic assessment is 3-dimensional (3D) motion analysis. However, 2-dimensional (2D) kinematic analysis is an objective and feasible alternative.

Objective:

To quantify the relationship between 2D and 3D hip and knee kinematics in single-leg drop landings and test for a set of 3D hip and knee kinematics that best predicts 2D kinematic measures during single-leg drop landings Design: Descriptive, comparative laboratory study.

Participants:

31 healthy college-age women (65.5 kg [SD 12.3], 168.1 cm [SD 6.7]).

Methods:

Participants performed five 40-cm single-leg landings during motion capture at 240 Hz. Multiple regressions were used to predict relationships for knee and hip between 2D frontal-plane projection angles (FPPA) and 3D measurements.

Results:

2D knee FPPA had a strong relationship with 3D frontal-plane knee kinematics at initial contact (IC) (r 2 = .72), which was only minimally improved with the addition of knee sagittal-plane and hip transverse-plane positions at IC (r 2 = .77). In contrast, 2D knee FPPA had a low relationship with 3D knee-abduction excursion (r 2 = .06). The addition of knee sagittal-plane and hip transverse-plane motions did not improve this relationship (r 2 = .14). 2D hip FPPA had a moderate relationship with 3D frontal-plane hip position at IC (r 2 = .52), which was strengthened with the addition of hip sagittal-plane position (r 2 = .60). In addition, hip 2D FPPA into adduction excursion had a strong association with 3D hip-adduction excursion (r 2 = .70).

Conclusion:

2D kinematics can predict 3D frontal-plane hip and knee position at IC during a single-leg landing but predict 3D frontal-plane knee excursion with far less accuracy.

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Andrew R. Boldt, John D. Willson, Joaquin A. Barrios and Thomas W. Kernozek

We examined the effects of medially wedged foot orthoses on knee and hip joint mechanics during running in females with and without patellofemoral pain syndrome (PFPS). We also tested if these effects depend on standing calcaneal eversion angle. Twenty female runners with and without PFPS participated. Knee and hip joint transverse and frontal plane peak angle, excursion, and peak internal knee and hip abduction moment were calculated while running with and without a 6° full-length medially wedged foot orthoses. Separate 3-factor mixed ANOVAs (group [PFPS, control] x condition [medial wedge, no medial wedge] x standing calcaneal angle [everted, neutral, inverted]) were used to test the effect of medially wedged orthoses on each dependent variable. Knee abduction moment increased 3% (P = .03) and hip adduction excursion decreased 0.6° (P < .01) using medially wedged foot orthoses. No significant group x condition or calcaneal angle x condition effects were observed. The addition of medially wedged foot orthoses to standardized running shoes had minimal effect on knee and hip joint mechanics during running thought to be associated with the etiology or exacerbation of PFPS symptoms. These effects did not appear to depend on injury status or standing calcaneal posture.

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Gabriel Andrade Paz, Marianna de Freitas Maia, Haroldo Gualter Santana, Humberto Miranda, Vicente Lima and John D. Willson

Study Design: Observational study. Context: Altered frontal plane knee mechanics during dynamic tasks have been often associated with lower-extremity injuries. Strategies to decrease these risk factors and improve knee joint stability are often applied in rehabilitation and training environments. Objective: The purpose of this study was to compare knee joint frontal plane projection angles (FPPA) via 2-dimensional video analysis during drop vertical jump (DVJ) and step-down test (SDT) tasks in the preferred and nonpreferred limbs of young male and female volleyball players. Methods: A total of 60 young male (n = 29) and female (n = 31) volleyball players (13.6 [1.1] y, 62.2 [11.2] kg, and 170.8 [10] cm) participated in this study. Once the athletes were screened for inclusion and exclusion criteria, limb preference was operationally defined as the preferred kicking leg or the foot used for stair climbing. In a randomized study design, participants were asked to perform a bilateral DVJ and unilateral step-down landing tasks for both preferred and nonpreferred limb. Kinematic analysis was performed via a 2-dimensional video recording of knee joint FPPA alignment. Results: No difference was noted in FFPA during DVJ and SDT tasks between preferred and nonpreferred limbs in both male and female groups (P > .05). The FFPA was significantly higher for both limbs during DVJ versus SDT in both groups (P ≤ .05), but it was not different between male and female athletes. Conclusions: Based on these findings, clinicians may expect young male and female volleyball athletes to demonstrate similar and symmetrical lower-extremity 2-dimensional knee joint FPPA values across screening tests intended to identify lower-extremity injury risk factors. However, greater FPPA values should be expected during the more dynamic DVJ task.