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Jocelyn F. Hafer and Katherine A. Boyer

Aging is associated with declining strength, 1 , 2 a downward shift in muscle torque–velocity characteristics, 3 slowing gait speed, 4 , 5 and changes in gait mechanics. 6 In particular, strength or power of the knee extensor muscles correlates with walking speed 4 , 7 , 8 and mobility

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Michelle M. McLeod, Phillip Gribble, Kate R. Pfile and Brian G. Pietrosimone

Context:

Arthroscopic partial meniscectomy (APM) after meniscal tear has been widely accepted and associated with quick return to activity. Unfortunately, meniscectomy is associated with risk for knee osteoarthritis, which may be attributed to postsurgical quadriceps weakness. This has important implications, as the quadriceps play a prominent role in knee stabilization and energy attenuation in the lower extremity.

Objective:

To determine the magnitude of interlimb quadriceps strength deficits in people with unilateral APM by systematically reviewing the current literature.

Evidence Acquisition:

The Web of Knowledge databases were searched on September 22, 2010, using terms meniscus OR meniscectomy AND quadriceps strength OR quadriceps weakness. Included articles were written in English, reporting means and SDs of isokinetic peak torque at 60° and 180°/s for both limbs.

Evidence Synthesis:

Four articles were included in the final analysis. Effect sizes and 95% confidence intervals (CI) were calculated between limbs for periods less than 1 mo, 1–3 mo, 3–6 mo, and more than 6 mo.

Conclusion:

Homogeneous effect sizes indicate quadriceps weakness in the involved limb. Effects were strong at less than 1 mo (d = −1.01 to −1.62), while weak to strong effects were found for 1–3 mo (d = −0.40 to −8.04) and 3–6 mo (d = −0.40 to −5.11). Weak effects were found at more than 6 mo (d = −0.30 to −0.37). Definitive effects with a CI not crossing zero were found in 65% of the data. Although APM patients return to function within weeks after surgery, prolonged quadriceps strength deficits may increase the risk of knee-joint degeneration. Furthermore, evidence of bilateral dysfunction after unilateral injury may suggest that neuromuscular deficits post-APM are greater than the interlimb differences found in this review. Further research should be conducted to determine the nature of strength deficits and the best methods for restoring strength after APM.

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José Messias Rodrigues da Silva, Marcia Uchoa de Rezende, Tânia Carvalho Spada, Lucila da Silva Francisco, Helenilson Pereira dos Santos, Robson de Andrade Souza, Júlia Maria D'Andréa Greve and Emmanuel Gomes Ciolac

that occurs in almost all physiological systems, knee osteoarthritis (KOA) is one of the most prevalent age-related chronic diseases. One in 4 people over 55 years of age has persistent knee pain, 3 resulting in reduced quality of life, that has a major impact on function and independence, 1

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Seung-uk Ko, Gerald J. Jerome, Eleanor M. Simonsick, Stephanie Studenski and Luigi Ferrucci

whether or how other factors affect gait characteristics among fallers are rare. Chronic musculoskeletal pain in older adults is associated with greater occurrence of falls ( Leveille et al., 2009 ). Specifically, knee pain, which effects approximately a quarter of older adults ( McAlindon, Snow, Cooper

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Mark D. Grabiner and Tammy M. Owings

For this study it was hypothesized that when participants intended to perform a maximum voluntary concentric (or eccentric) contraction but had an eccentric (or concentric) contraction imposed upon them, the initial EMG measured during the isometric phase preceding the onset of the dynamometer motion would reflect the intended contraction condition. The surface EMG of the vastus lateralis muscle was measured in 24 participants performing isokinetic concentric and eccentric maximum voluntary knee extensor contractions. The contractions were initiated from rest and from the same knee flexion angle and required the same level of external force to trigger the onset of dynamometer motion. Vastus lateralis EMG were quantified during the isometric phase preceding the onset of the dynamometer motion. When participants intended to perform a concentric contraction but had an eccentric contraction imposed upon them, the initial EMG resembled that of a concentric contraction. When they intended to perform an eccentric contraction but had a concentric contraction imposed upon them, the initial EMG resembled that of an eccentric contraction. Overall, the difference between concentric and eccentric contractions observed during the period of the initial muscle activation implies that descending signals include information that distinguishes between eccentric and concentric contractions.

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John H. Hollman, Robert H. Deusinger, Linda R. Van Dillen, Dequan Zou, Scott D. Minor, Matthew J. Matava and Jack R. Engsberg

Context:

Analyses of the path of instant center of rotation (PICR) can be used to infer joint-surface rolling and sliding motion (arthrokinematics). Previous PICR research has not quantified arthrokinematics during weight-bearing (WB) movement conditions or studied the association of muscle activity with arthrokinematics.

Objective:

To examine tibiofemoral arthrokinematics and thigh-muscle EMG during WB and non-weight-bearing (NWB) movement.

Design:

2 x 9 repeated-measures experiment.

Setting:

Laboratory.

Participants:

11 healthy adults (mean age 24 years).

Main Outcome Measures:

Tibiofemoral percentage rolling arthrokinematics and quadriceps: hamstring EMG activity.

Results:

WB percentage rolling (76.0% ± 4.7%) exceeded that of NWB (57.5% ± 1.8%) through terminal knee extension (F 8,80 = 8.99, P < .001). Quadriceps:hamstring EMG ratios accounted for 45.1% and 34.7% of the variance in arthrokinematics throughout the WB and NWB movement conditions, respectively (P < .001).

Conclusions:

More joint-surface rolling occurs through terminal knee extension during WB movement and is associated with an increase in hamstring activity.

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Maria Angelika Peer and Nigel Gleeson

Mechanical loading of the knee joint can often exceed the tensile capacities of the passive structures 1 during strenuous activities, with greater reliance placed on protection from surrounding musculature to maintain joint integrity. 2 Optimal muscle functioning is considered fundamental to

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Nicholas M. Brisson, Paul W. Stratford, Saara Totterman, José G. Tamez-Peña, Karen A. Beattie, Jonathan D. Adachi and Monica R. Maly

Investigations of joint loading in knee osteoarthritis (OA) typically normalize the knee adduction moment to global measures of body size (eg, body mass, height) to allow comparison between individuals. However, such measurements may not reflect knee size. This study used a morphometric measurement of the cartilage surface area on the medial tibial plateau, which better represents medial knee size. This study aimed to determine whether normalizing the peak knee adduction moment and knee adduction moment impulse during gait to the medial tibial bone–cartilage interface could classify radiographic knee OA severity more accurately than traditional normalization techniques. Individuals with mild (N = 22) and severe (N = 17) radiographic knee OA participated. The medial tibial bone–cartilage interface was quantified from magnetic resonance imaging scans. Gait analysis was performed, and the peak knee adduction moment and knee adduction moment impulse were calculated in nonnormalized units and normalized to body mass, body weight × height, and the medial tibial bone–cartilage interface. Receiver operating characteristic curves compared the ability of each knee adduction moment normalization technique to classify participants according to radiographic disease severity. No normalization technique was superior at distinguishing between OA severities. Knee adduction moments normalized to medial knee size were not more sensitive to OA severity.

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Peter R. Blanpied

Closed kinetic chain exercises are commonly used in strengthening and rehabilitation programs. Altering positions of body segments and supports might affect the way these exercises are performed. The purpose of this study was to compare gluteal, quadriceps, hamstring, and plantar flexor muscle activations during wall-slide (WS) vs. squat-machine (SM) exercise. In addition, the effects of support location and foot position were investigated. Twenty women performed 8 exercises, to 60° of knee flexion. Results indicated that placing the foot forward caused an increase in all muscle activations except in the plantar flexors, which showed an increase with the foot placed in line with the hip. This effect was exaggerated during WS for the plantar flexors and quadriceps and during SM for the hamstrings. When the support was located at the scapular level, hamstring and gluteal activations were greater, and quadriceps activity was less during SM than during WS. These results could be used to target specific muscle groups during strengthening exercise.

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Jamie L. Shapiro, Britton W. Brewer, Allen E. Cornelius and Judy L. Van Raalte

The purposes of this study were to investigate patterns of emotional response to reconstructive surgery of the anterior cruciate ligament (ACL) of the knee following sport injury and to examine the extent to which neuroticism differed across patterns of adjustment. Participants were 73 patients (51% recreational athletes, 46% competitive athletes, 3% nonathletes) who had ACL reconstruction surgery and who had low levels of negative mood before surgery. Participants completed measures of personality and negative mood before surgery and completed daily assessments of negative mood for 6 weeks postsurgery. The negative mood of participants was classified into three patterns for two different time periods. Participants with patterns of resilience outnumbered those with patterns of disturbance. Participants with patterns involving mood disturbance one week after surgery had significantly higher presurgery neuroticism levels. Practitioners should target individuals with high neuroticism before surgery for emotion management interventions to prevent mood disturbance following ACL surgery.