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Jonathan Sinclair and Paul J. Taylor

/competitive sports activities. 3 ACL pathologies are extremely serious, leading to a long-term cessation from training/competition. 4 Furthermore, ACL injury is typically associated with chronic knee discomfort that ultimately leads to forced retirement from competition in many cases. 5 Importantly, Roos et al 6

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Daniël M. van Leeuwen, Fabian van de Bunt, Cornelis J. de Ruiter, Natasja M. van Schoor, Dorly J.H. Deeg and Kaj S. Emanuel

Knee osteoarthritis (OA) represents an increasing burden in developed countries ( Arden & Nevitt, 2006 ). Progression of knee OA is usually assessed using radiographic scores such as the Kellgren & Lawrence scale (K&L-score) ( Kellgren & Lawrence, 1957 ). Radiographic scores correlate to some

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Stefan M. Gabriel, Anton G. Clifford, William J. Maloney, Mary K. O’Connell and Paul Tornetta III

Medial knee osteoarthritis (OA) is a common disorder often associated with pathologic joint loading. Insoles, braces, and high tibial osteotomy are OA treatments aimed at reducing medial joint loads, but their use and effectiveness are limited. The KineSpring System implant also intends to reduce knee loads in OA patients while overcoming those limitations. The current study was undertaken to test the implant’s effect on loads at the knee. Six cadaver knees with Outerbridge Grade I-II medial OA were subjected to simulated gait using a kinematic test system. Knees were tested with and without the medial knee implant while thin film sensors measured medial and lateral femorotibial contact pressures. Significant medial compartment load reductions (134 ± 53 N [P = .002]) were found throughout the stance phase of gait in the treated knee. Significant total joint load decreases (91 ± 40 N [P = .002]) were also observed without substantial changes in lateral compartment loads. These significant reductions of medial and total intra-articular loads are also within clinically effective ranges of other unloading systems. This suggests that the KineSpring System could be a viable treatment for medial knee OA.

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John P. Miller, James C. Vailas, Ronald V. Croce, Robert Confessore and Kerriann Catlaw

This study examined the effects of (a) functional knee braces on thigh muscle EMG and (b) physical activity and leg shape on knee brace migration. Ten female college ice hockey players were fitted with a strap-secured functional knee brace (SSB) and a hard-shell functional knee brace with strapping. Participants performed a side-step maneuver, a treadmill ran, and an obstacle course. Significant differences were noted in hamstring and quadriceps EMG median frequency (mfEMG) while wearing the SSB compared with the control condition. Significant downward shifts were noted in hamstring mfEMG for both braces when compared with the control condition. There was greater brace migration for the obstacle course for both brace types. No relation was found between leg shape and the amount of migration. This study suggests that custom-fitted functional knee braces alter the motor unit recruitment patterns of the thigh musculature during physical activity and that they do not migrate significantly during physical activity.

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Nicholas H. Yang, Paul K. Canavan and Hamid Nayeb-Hashemi

Subject-specific models were developed and finite element analysis was performed to observe the effect of the frontal plane tibiofemoral angle on the normal stress, Tresca shear stress and normal strain at the surface of the knee cartilage. Finite element models were created for three subjects with different tibiofemoral angle and physiological loading conditions were defined from motion analysis and muscle force mathematical models to simulate static single-leg stance. The results showed that the greatest magnitude of the normal stress, Tresca shear stress and normal strain at the medial compartment was for the varus aligned individual. Considering the lateral knee compartment, the individual with valgus alignment had the largest stress and strain at the cartilage. The present investigation is the first known attempt to analyze the effects of tibiofemoral alignment during single-leg support on the contact variables of the cartilage at the knee joint. The method could be potentially used to help identify individuals most susceptible to osteoarthritis and to prescribe preventive measures.

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Michael A. Samaan, Matthew C. Hoch, Stacie I. Ringleb, Sebastian Bawab and Joshua T. Weinhandl

The aim of this study was to determine the effects of hamstrings fatigue on lower extremity joint coordination variability during a sidestep cutting maneuver. Twenty female recreational athletes performed five successful trials of a sidestep cutting task preand postfatigue. Each participant completed an isolated hamstrings fatigue protocol consisting of isokinetic maximum effort knee flexion and passive extension contractions. Vector coding was used to examine hip and knee joint couplings (consisting of various planar motions) during the impact and weight acceptance phases of the sidestep cut stance phase. Paired t tests were used to analyze differences of each phase as an effect of fatigue, where alpha was set a priori at .05. The hip rotation/knee rotation coupling exhibited a significant decrease in coordination variability as a function of fatigue in both the impact (P = .015) and weight acceptance phases (P = .043). Similarly, the hip adduction-abduction/knee rotation coupling exhibited a significant decrease in coordination variability in the weight acceptance phase (P = .038). Hamstrings fatigue significantly decreased coordination variability within specific lower extremity joint couplings that included knee rotation. Future studies should be conducted to determine if this decrease in coordination variability is related to lower extremity injury mechanisms.

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Amber Collins, Troy Blackburn, Chris Olcott, Joanne M. Jordan, Bing Yu and Paul Weinhold

Extended use of knee sleeves in populations at risk for knee osteoarthritis progression has shown functional and quality of life benefits; however, additional comprehensive kinematic and kinetic analyses are needed to determine possible physical mechanisms of these benefits which may be due to the sleeve’s ability to enhance knee proprioception. A novel means of extending these enhancements may be through stochastic resonance stimulation. Our goal was to determine whether the use of a knee sleeve alone or combined with stochastic resonance electrical stimulation improves knee mechanics in knee osteoarthritis. Gait kinetics and kinematics were assessed in subjects with medial knee osteoarthritis when presented with four conditions: control1, no electrical stimulation/sleeve, 75% threshold stimulation/sleeve, and control2. An increase in knee flexion angle throughout stance and a decrease in flexion moment occurring immediately after initial contact were seen in the stimulation/sleeve and sleeve alone conditions; however, these treatment conditions did not affect the knee adduction angle and internal knee abduction moment during weight acceptance. No differences were found between the sleeve alone and the stochastic resonance with sleeve conditions. A knee sleeve can improve sagittal-plane knee kinematics and kinetics, although adding the current configuration of stochastic resonance did not enhance these effects.

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Sevgi S. Subasi, Nihal Gelecek and Gazanfer Aksakoglu

Context:

There is limited information on the effects of different warm-up periods on proprioception and balance in the context of injury prevention.

Objective:

To determine the effects of warm-up exercises on knee proprioception and balance and to compare the effectiveness of warming up periods.

Design:

Pretest/posttest.

Setting:

Research laboratory.

Participants:

30 healthy subjects (19 women, 11 men; mean age 20.70 ± 0.99 years).

Interventions:

Exercise groups performed warm-up exercises (group 1, 5 minutes; group 2, 10 minutes). Joint Position Sense (JPS) was tested at 15°, 30°, and 60° knee flexion (KF) on a JPS device. Balance was measured using the Neurocom Balance Master System.

Main Outcome Measures:

JPS absolute error (AE) was measured at 15°, 30°, and 60° KF and postural control was measured.

Results:

After exercise, we found significant improvements for AE of JPSs of 30° right (R) KF, 15° left (L) KF, and 60° L KF in group 1. In group 2, AE of JPS values increased for all angles of both knees except 60° R KF. AE of JPS values of 15° R KF, 30° R KF, 15° L KF, 60° L KF were significantly different in group 2 compared with group 1. In balance measurements, there were significant improvements for standing on foam with eyes closed (EC) position, velocity and R-L unilateral stance EC in group 1. There were significant improvements for velocity, end point, maximum excursion, and L unilateral stance EC in group 2.

Conclusions:

Both warm-up periods have positive effects on knee proprioception and balance. The 10-minute warm-up exercise improved proprioception by a greater amount than the 5 minutes warm-up exercise.

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Mary Hellen Morcelli, Dain Patrick LaRoche, Luciano Fernandes Crozara, Nise Ribeiro Marques, Camilla Zamfolini Hallal, Mauro Gonçalves and Marcelo Tavella Navega

gait speed. 7 , 8 Poor lower limb strength has been associated with slow gait speed and the likelihood of falling, making it an important predictor of functional status in older adults. 9 – 12 The association exists because joint torques at the hip, knee, and ankle are summed in a coordinated fashion

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Jonathan A. Gastel, John A. Bergfeld, Gary J. Calabrese and Robert S. Gray