Hip Abductor Weakness and Its Association With New or Worsened Knee Pain: Data From the Multicenter Osteoarthritis Study.

Objective: Hip abductors, important for controlling pelvic and femoral orientation during gait, may affect knee pain. Our objective was to evaluate the relation of hip abductor strength to worsened or new-onset frequent knee pain. Given previously noted associations of knee extensor strength with osteoarthritis in women, we performed sex-specific analyses.

Changes in Walking Biomechanics after a 30-Min Exercise Bout in Sedentary Compared with Active Young Women.

Introduction: Patellofemoral pain (PFP) is a common overuse injury associated with physical activity, including walking. The risk for PFP may increase if walking biomechanics change during a bout of walking. Because walking for exercise is often recommended to previously sedentary adults, this would be a cause for concern.

Examination of Corticospinal and Spinal Reflexive Excitability During the Course of Postoperative Rehabilitation After Anterior Cruciate Ligament Reconstruction.

Objective: To investigate corticospinal and spinal reflexive excitability and quadriceps strength in healthy athletes and athletes after anterior cruciate ligament reconstruction (ACLR) over the course of rehabilitation.

Design: Prospective cohort study.

Methods: Eighteen athletes with ACLR and 18 healthy athletes, matched by sex, age, and activity, were tested at (1) 2 weeks after surgery, (2) the "quiet knee" time point, defined as full range of motion and minimal effusion, and (3) return to running, defined as achieving a quadriceps index of 80% or greater.

Athletes after anterior cruciate ligament reconstruction demonstrate asymmetric intracortical facilitation early after surgery.

Quadriceps dysfunction persists after anterior cruciate ligament reconstruction (ACLR), yet the etiology remains elusive. Inhibitory and facilitatory intracortical networks (ie, intracortical excitability) may be involved in quadriceps dysfunction, yet the investigation of these networks early after ACLR is sparse. The purposes of this study were to examine (a) changes in intracortical excitability in athletes after ACLR compared to uninjured athletes during the course of postoperative rehabilitation, (b) the association between intracortical excitability and quadriceps strength in athletes after ACLR.

Lower Quadriceps Rate of Force Development Is Associated With Worsening Physical Function in Adults With or at Risk for Knee Osteoarthritis: 36-Month Follow-Up Data From the Osteoarthritis Initiative.

Objective: To determine the association between quadriceps rate of force development (RFD) and decline in self-reported physical function and objective measures of physical performance.

Design: Longitudinal cohort study.

Setting: Community-based sample from 4 urban areas.

Knee Extensor Rate of Torque Development Before and After Arthroscopic Partial Meniscectomy, With Analysis of Neuromuscular Mechanisms.

Study Design Descriptive, prospective single-cohort longitudinal study. Background Though rapid torque development is essential in activities of daily living and sports, it hasn't been specifically tested by most physical therapists or incorporated into rehabilitation programs until late in the treatment process. Little evidence is available on quadriceps torque development capacity before and after arthroscopic knee surgery.

Efficacy of blood flow-restricted, low-load resistance training in women with risk factors for symptomatic knee osteoarthritis.

Objective: To assess whether concurrent blood flow restriction (BFR) during low-load resistance training is an efficacious and tolerable means of improving quadriceps strength and volume in women with risk factors for symptomatic knee osteoarthritis (OA).

Design: Randomized, double-blinded, controlled trial.

Setting: Exercise training clinical research laboratory.

Effect of knee joint angle on side-to-side strength ratios.

Isometric knee extensor and flexor strength are typically tested at different joint angles due to the differences in length-tension relationships of the quadriceps and hamstring muscles. The efficiency of strength testing can be improved if the same angle can be used to test both the knee extensor and flexor muscle groups. The aim of this study was to determine an optimal angle for isometric knee strength testing by examining the effect of knee angle on side-to-side peak torque ratios.

Comparison of T1ρ, dGEMRIC, and quantitative T2 MRI in preoperative ACL rupture patients.

Rationale And Objectives: T1ρ, inversion recovery sequence with a gadolinium contrast agent (dGEMRIC), and T2 mapping have shown sensitivity toward different osteoarthritic-associated compositional changes after joint injury, but have not been studied concomitantly in vivo. We hypothesized that these magnetic resonance imaging sequences can be used to measure early glycosaminoglycan (GAG) losses and collagen disruption in cartilage of anterior cruciate ligament (ACL) rupture patients.

Materials And Methods: Thirteen acute ACL rupture patients were each imaged during a 4-hour presurgery workup to acquire a fast-spin-echo-based T1ρ sequence, a multi-echo spin-echo T2 sequence, and T1-weighted dGEMRIC an average of 55.

Integrating carthage-specific T1rho MRI into knee clinic diagnostic imaging.

With a rise in post-traumatic osteoarthritis, OA no longer is considered just a disease of aging. The 'gold standard' for OA diagnosis has long been planar radiographs for visualizing osteophytes, joint space narrowing and sclerotic changes. A typical magnetic resonance imaging (MRI) protocol will acquire proton density, T1, T2, and fat suppressed images that give a comprehensive picture of morphologic changes associated with injury and subsequent degenerative processes.

Effect of knee position on quadriceps muscle force steadiness and activation strategies.

Introduction: In this study we investigated the effect of knee position on quadriceps force steadiness and activation strategies.

Methods: Quadriceps force steadiness was evaluated in 22 volunteers at two knee positions by testing their ability to regulate submaximal force. Muscle activation strategies were studied in both time and frequency domains using surface electromyography.

Factors explaining chronic knee extensor strength deficits after ACL reconstruction.

Persistent quadriceps muscle weakness is common after anterior cruciate ligament (ACL) reconstruction. The mechanisms underlying these chronic strength deficits are not clear. This study examined quadriceps strength in people 2-15 years post-ACL reconstruction and tested the hypothesis that chronic quadriceps weakness is related to levels of voluntary quadriceps muscle activation, antagonistic hamstrings moment, and peripheral changes in muscle.

Intraoperative femoral nerve stimulation in evaluation of patellar tracking: tourniquet effects and catheter placement.

Background: Dynamic intraoperative assessment of patella tracking utilizes femoral nerve stimulation to contract the quadriceps muscles in assessing the proper distance to transfer the tibial tubercle during distal realignment procedures for patellofemoral instability.

Purpose: We describe the effects of tourniquet inflation and catheter placement on intraoperative femoral nerve stimulation for assessment of patellar tracking.

Methods: Percutaneous electromyographic (EMG) needles were placed into the quadriceps and sartorius muscles to monitor muscle activity and changes in amplitude threshold (mA) required for femoral nerve stimulation with increasing tourniquet inflation times.

Rehabilitation of syndesmotic (high) ankle sprains.

Context: High ankle sprains are common in athletes who play contact sports. Most high ankle sprains are treated nonsurgically with a rehabilitation program.

Evidence Acquisition: All years of PUBMED, Cochrane Database of Systematic Reviews, CINAHL PLUS, SPORTDiscuss, Google Scholar, and Web of Science were searched to August 2010, cross-referencing existing publications.

Quantification method affects estimates of voluntary quadriceps activation.

The aim of this study was to investigate the effect of quantification method on estimates of voluntary quadriceps muscle activation. Twenty-two people with no history of serious lower extremity injuries underwent voluntary quadriceps activation testing at 60 degrees of knee flexion. Estimates of quadriceps activation were derived with: (1) a formula based on the interpolated twitch technique (ITT); (2) the central activation ratio (CAR); and (3) a modified central activation ratio.

Error associated with antagonist muscle activity in isometric knee strength testing.

The purpose of this study was to determine the measurement error associated with antagonist muscle activity in isometric knee strength testing at 60 degrees of knee flexion in both sexes. Muscle specific EMG-contraction intensity relationships were obtained from 22 young people by having them match moment targets ranging from 10% to 100% peak moment. The moments attributed to each of the quadriceps and hamstrings muscles were partitioned using a practical mathematical model.

Variability in antagonist muscle activity and peak torque during isometric knee strength testing.

Background & Objective: Strength testing is common in the treatment of people with knee pathology and in research related to knee health. Variability in the magnitude of antagonist muscle activity and peak torque measurements during isometric knee strength testing is not well defined and has potential implications of strength test validity and reliability. The aim of this study was to determine the magnitude and variability (side-to-side, session-to-session) of antagonist muscle activity and peak torque during isometric knee strength testing and to compare and contrast the results of males and females.

Sex differences in quadriceps and hamstrings EMG-moment relationships.

Purpose: To evaluate sex differences in quadriceps and hamstrings muscle EMG-moment relationships when the muscles were acting as agonists and antagonists across the range of contraction intensity.

Methods: Twenty-two age- and activity-level-matched young people (11 females, 11 males) with no history of serious lower extremity injuries participated in this study. Muscle-specific EMG-moment relationships were determined for the quadriceps and hamstrings muscles when acting as agonists and antagonists during isometric target matching at 10 loads ranging from 10% to 100% peak moment.

Torque-based triggering improves stimulus timing precision in activation tests.

The aim of this study was to assess whether automated torque-based stimulator triggering could improve precision in delivering stimuli near peak torque during voluntary activation tests. The quadriceps activation test was used as a test model in 11 volunteers. Automated torque-based triggering reduced stimulus delivery timing errors by 75% when compared with conventional automated time-based triggering.

Evoked tetanic torque and activation level explain strength differences by side.

Previous studies have demonstrated that healthy young people typically have side-to-side differences in knee strength of about 10% when the peak torque generated by the stronger leg is contrasted with that of the weaker leg. However, the mechanisms responsible for side-to-side differences in knee strength have not been clearly defined. The current study tested the hypothesis that side-to-side knee extensor strength differences are explained by inter-limb variations in voluntary activation, antagonistic hamstrings activity, and electrically evoked torque at rest.

Hamstrings activity during knee extensor strength testing: effects of burst superimposition.

Quadriceps muscle strength is often used as a criterion for functional progression and return to activity after knee joint injury or surgery. Previous research has demonstrated that noteworthy antagonist activity is present during knee strength testing. the countermoment associated with this antagonist muscle activity may lead to an underestimation of knee strength.

A systematic review of anterior cruciate ligament reconstruction rehabilitation: part II: open versus closed kinetic chain exercises, neuromuscular electrical stimulation, accelerated rehabilitation, and miscellaneous topics.

Anterior cruciate ligament (ACL) reconstruction is a common surgical knee procedure that requires intensive postoperative rehabilitation by the patient. A variety of randomized controlled trials have investigated aspects of ACL reconstruction rehabilitation. A systematic review of English language level 1 and 2 studies identified 54 appropriate randomized controlled trials of ACL rehabilitation.

A systematic review of anterior cruciate ligament reconstruction rehabilitation: part I: continuous passive motion, early weight bearing, postoperative bracing, and home-based rehabilitation.

Anterior cruciate ligament (ACL) reconstruction is a common surgical knee procedure that requires intensive postoperative rehabilitation by the patient. A variety of randomized controlled trials have investigated aspects of ACL reconstruction rehabilitation. A systematic review of English language level 1 and 2 studies identified 54 appropriate randomized controlled trials of ACL rehabilitation.

Quadriceps and hamstrings muscle control in athletic males and females.

The aim of this study was to investigate whether athletic males and females have differences in their quadriceps and hamstrings muscle control strategies. Twenty-four people (12 males, 12 females) active in level I activities volunteered to participate. The subjects' muscle control strategies were studied using electromyography and a target matching protocol that assesses one's ability to produce force with control.

Syndesmotic ankle sprains in athletes.

Ankle sprains are among the most common athletic injuries and represent a significant source of persistent pain and disability. Despite the high incidence of ankle sprains in athletes, syndesmosis injuries have historically been underdiagnosed, and assessment in terms of severity and optimal treatment has not been determined. More recently, a heightened awareness in sports medicine has resulted in more frequent diagnoses of syndesmosis injuries.