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Lei Zhou, Marie-Anne Gougeon and Julie Nantel

; Lim, Huang, Wu, Girardi, & Cammisa, 2007 ). PD also leads to changes in gait power profiles at the ankle, knee, and hip, which account for reduction in stride length and gait speed ( Lim et al., 2007 ; Morris, Huxham, McGinley, Dodd, & Iansek, 2001 ; Sofuwa et al., 2005 ; Winter, 1987 ). Growing

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Lee E. Brown, Michael Whitehurst and David N. Buchalter

A 67-year-old male underwent bilateral total knee replacement surgery and was subsequently placed on a bilateral isokinetic knee rehabilitation program. Isokinetic knee testing was performed on unilateral dominant (UD; right) and nondominant (UND; left) limbs as well as bilateral limbs (BLs) before and after a three-times-per-week, 8-week protocol during which the patient followed a bilateral isokinetic velocity spectrum (60 to 300°/s) rehabilitation program. The protocol was made possible by the introduction of a new bilateral isokinetic knee attachment developed by the authors. The BL extension and flexion peak torque increased 41% and 51% at 60°/s, respectively. The UD and UND extension peak torque increased 22% and 37%, respectively, while flexion peak torque increased 68% and 52%, respectively. The bilateral deficit decreased with increasing velocity for both extension and flexion. These results demonstrate that a bilateral isokinetic approach to rehabilitation may be a legitimate technique to increase knee extension and flexion peak torque both unilaterally and bilaterally following bilateral total knee replacement surgery.

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Renato Semadeni and Kai-Uwe Schmitt

Objective:

In this study a numerical model of a skier was developed to investigate the effect of different rehabilitation strategies after anterior cruciate ligament (ACL) rupture.

Methods:

A computer model using a combined finite-element and multibody approach was established. The model includes a detailed representation of the knee structures, as well as all major leg muscles. Using this model, different strategies after ACL rupture were analyzed.

Results:

The benefit of muscle training to compensate for a loss of the ACL was shown. The results indicate that an increase of 10% of the physiological cross-sectional area has a positive effect without subjecting other knee structures to critical loads. Simulating the use of a hamstring graft indicated increasing knee loads. A patellar-tendon graft resulted in an increase of the stress on the lateral collateral ligament.

Conclusion:

Muscle training of both extensors and flexors is beneficial in medical rehabilitation of ACL-deficient and ACL-reconstructed knees.

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Robert English, Mary Brannock, Wan Ting Chik, Laura S. Eastwood and Tim Uhl

Context:

Lower extremity functional testing assesses strength, power, and neuro-muscular control. There are only moderate correlations between distance hopped and isokinetic strength measures.

Objective:

Determine if incorporating body weight in the single-leg hop for distance increases the correlation to isokinetic measures.

Study Design:

Correlational study.

Setting:

Musculoskeletal laboratory.

Participants:

30 healthy college students; 15 men and 15 women; ages 18 to 30 years.

Main Outcome Measures:

Isokinetic average peak torque and total work of quadriceps and hamstrings and single-leg hop work and distance.

Results:

Significant correlations include hop work to total-work knee extension (r = .89), average peak-torque knee extension (r = .88), distance hopped to total-work knee extension (r = .56) and average peak-torque knee extension (r = .63). Correlations involving hop work were greater than distance hopped (P < .05).

Conclusions:

Use of body weight in the assessment of distance hopped provides better information about the patient’s lower extremity strength and ability than the distance hopped alone.

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Jocelyn F. Hafer, Mark S. Miller, Jane A. Kent and Katherine A. Boyer

-related decline in knee extensor strength and power compared with males. 4 , 14 , 18 , 19 This sex-specific difference in age-related knee extensor decline could be problematic as these muscles are important for stance phase support and propulsion during locomotion. 20 In addition to a sex-specific difference

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Karl Fullam, Brian Caulfield, Garrett F. Coughlan, Wayne McNulty, David Campbell and Eamonn Delahunt

impairments that could contribute to lower-limb injury. 17 , 18 Decreased postural balance is a primary risk factor for knee joint injury. 19 Furthermore, Coughlan et al 20 recently recommended the utilization of dynamic postural balance testing as part of a weekly musculoskeletal screening assessment to

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Daniel W. Sample, Tanner A. Thorsen, Joshua T. Weinhandl, Kelley A. Strohacker and Songning Zhang

Individuals who are obese often present more extreme gait biomechanics including increased ground reaction forces (GRFs) and joint contact forces compared with healthy-weight individuals. 1 Obesity can lead to many other diseases, one of which being osteoarthritis (OA). The knee, specifically, is

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Karl F. Orishimo and Ian J. Kremenic

The objective of this study was to measure adaptations in landing strategy during single-leg hops following thigh muscle fatigue. Kinetic, kinematic, and electromyographic data were recorded as thirteen healthy male subjects performed a single-leg hop in both the unfatigued and fatigued states. To sufficiently fatigue the thigh muscles, subjects performed at least two sets of 50 step-ups. Fatigue was assessed by measuring horizontal hopping ability following the protocol. Joint motion and loading, as well as muscle activation patterns, were compared between fatigued and unfatigued conditions. Fatigue significantly increased knee motion (p = 0.012) and shifted the ankle into a more dorsiflexed position (p = 0.029). Hip flexion was also reduced following fatigue (p = 0.042). Peak extension moment tended to decrease at the knee and increase at the ankle and hip (p = 0.014). Ankle plantar flexion moment at the time of peak total support moment increased from 0.8 (N⋅m)/kg (SD, 0.6 [N⋅m]/kg) to 1.5 (N⋅m)/kg (SD, 0.8 [N⋅m]/kg) (p = 0.006). Decreased knee moment and increased knee flexion during landings following fatigue indicated that the control of knee motion was compromised despite increased activation of the vastus medialis, vastus lateralis, and rectus femoris (p = 0.014, p = 0.014, and p = 0.017, respectively). Performance at the ankle increased to compensate for weakness in the knee musculature and to maintain lower extremity stability during landing. Investigating the biomechanical adaptations that occur in healthy subjects as a result of muscle fatigue may give insight into the compensatory mechanisms and loading patterns occurring in patients with knee pathology. Changes in single-leg hop landing performance could be used to demonstrate functional improvement in patients due to training or physical therapy.

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Nelson Cortes, James Onate, João Abrantes, Linda Gagen, Elizabeth Dowling and Bonnie Van Lunen

The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79° ± 11.78°) resulted in significantly (p = .001) less hip flexion than did the self-preferred (41.25° ± 12.89°) and rear foot (43.15° ± 11.77°) techniques. At peak vertical ground reaction force, the rear foot technique (26.77° ± 9.49°) presented significantly lower (p = .001) knee flexion angles as compared with forefoot (58.77° ± 20.00°) and self-preferred (54.21° ± 23.78°) techniques. A significant difference for knee valgus angles (p = .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12° ± 7.51°) and forefoot (4.97° ± 7.90°) techniques presented greater knee varus angles as compared with the rear foot technique (0.08° ± 6.52°). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.

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Elisabeth Macrum, David Robert Bell, Michelle Boling, Michael Lewek and Darin Padua

Context:

Limitations in gastrocnemius/soleus flexibility that restrict ankle dorsiflexion during dynamic tasks have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in its development.

Objective:

To determine the effect of restricted ankle-dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. The authors hypothesized that restricted ankle-dorsiflexion ROM would alter knee kinematics and lower extremity EMG during a squat.

Design:

Cross-sectional.

Participants:

30 healthy, recreationally active individuals without a history of lower extremity injury.

Interventions:

Each participant performed 7 trials of a double-leg squat under 2 conditions: a nowedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12° forefoot angle to simulate reduced plantar-flexor flexibility.

Main Outcome Measures:

3-dimensional hip and knee kinematics, medial knee displacement (MKD), and ankle-dorsiflexion angle. EMG of vastus medialis oblique (VMO), vastus lateralis (VL), lateral gastrocnemius (LG), and soleus (SOL). One-way repeated-measures ANOVAs were performed to determine differences between the W and NW conditions.

Results:

Compared with the NW condition, the wedge produced decreased peak knee flexion (P < .001, effect size [ES] = 0.81) and knee-flexion excursion (P < .001, ES = 0.82) while producing increased peak ankle dorsiflexion (P = .006, ES = 0.31), ankle-dorsiflexion excursion (P < .001, ES = 0.31), peak knee-valgus angle (P = .02, ES = 0.21), and MKD (P < .001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = .049, ES = 0.20) activity decreased while soleus activity increased (P = .03, ES = 0.64) compared with the NW condition. No changes were seen in hip kinematics (P > .05).

Conclusions:

Altering ankle-dorsiflexion starting position during a double-leg squat resulted in increased knee valgus and MKD, as well as decreased quadriceps activation and increased soleus activation. These changes are similar to those seen in people with PFP.