Muscle and tendon morphology after reconstruction of the anterior cruciate ligament with autologous semitendinosus-gracilis graft.

Background: The autologous semitendinosus-gracilis graft is the first choice of many orthopaedic surgeons when reconstructing the anterior cruciate ligament. The effect that graft harvest has on muscle and tendon morphology remains unclear. The purpose of this study was to describe these effects more completely.

Control of frontal plane knee laxity during gait in patients with medial compartment knee osteoarthritis.

Objective: Patients with medial compartment knee osteoarthritis (OA) adopt an abnormal gait pattern, and often develop frontal plane laxity at the knee. The purpose of this study was to quantify the extent of frontal plane knee joint laxity in patients with medial knee OA and genu varum and to assess the effect of joint laxity on knee joint kinetics, kinematics and muscle activity during gait.

Design: Twelve subjects with genu varum and medial compartment knee osteoarthritis (OA group) and 12 age-matched uninjured subjects underwent stress radiography to determine the presence and magnitude of frontal plane laxity.

A prospective analysis of incidence and severity of quadriceps inhibition in a consecutive sample of 100 patients with complete acute anterior cruciate ligament rupture.

Background: Weakness of the quadriceps femoris muscle after anterior cruciate ligament injury and reconstruction has been attributed to incomplete voluntary activation of the muscle. The literature is conflicting on the incidence of incomplete voluntary quadriceps activation after anterior cruciate ligament injury because of differences in testing methods and population biases. The purpose of this study was to systematically examine the incidence and severity of quadriceps voluntary activation failure in both lower extremities after acute anterior cruciate ligament injury.

Effect of dynamic stability on a step task in ACL deficient individuals.

Stair ascent and descent requires large knee motions and muscle forces that can be challenging for people with anterior cruciate ligament (ACL) deficiency. Movement and muscle activity patterns were compared in two groups of ACL deficient subjects and a group of uninjured subjects. The ACL deficient subjects were prospectively classified according to functional ability.

Altered quadriceps control in people with anterior cruciate ligament deficiency.

Purpose: The purpose of this study was to determine whether similar patterns of quadriceps dysfunction are observed when people with anterior cruciate ligament (ACL) deficiency perform static and dynamic tasks.

Methods: EMG data were collected from 15 subjects with an ACL deficient knee and 15 uninjured subjects as they performed static and dynamic tasks that were isolated to the knee and presented no threat to joint stability. The dynamic task was cyclic flexion and extension in the terminal 30 degrees of knee extension; the static task was an established isometric target-matching protocol.

Differences in normal and perturbed walking kinematics between male and female athletes.

Objective: To identify differences in lower extremity kinematic movement patterns between genders during walking through the application of an expected perturbation.

Design: Randomized limb kinematics were compared between healthy active males and females.

Background: Lower extremity kinematics during jump landing and cutting have been implicated as a potential source of the discrepancy in anterior cruciate ligament injury rates between genders.

Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series.

Study Design: A case series.

Objectives: The purpose of this case series was to assess the effect of high-intensity neuromuscular electrical stimulation (NMES) on quadriceps strength and voluntary activation following total knee arthroplasty (TKA).

Background: Following TKA, patients exhibit long-term weakness of the quadriceps and diminished functional capacity compared to age-matched healthy controls.

Quadriceps femoris muscle weakness and activation failure in patients with symptomatic knee osteoarthritis.

Purpose: Quadriceps weakness is common in patients with knee osteoarthritis (OA), and has been attributed to failure of voluntary activation. Methodological differences may have contributed to previous reports of extensive failure of voluntary activation in patients with osteoarthritis. The purpose of this study was to determine the extent of quadriceps muscle weakness and activation failure in middle aged patients with symptomatic medial knee osteoarthritis using maximum voluntary isometric contractions (MVIC) and a burst superimposition technique.

Eccentric muscle contractions: their contribution to injury, prevention, rehabilitation, and sport.

Muscles operate eccentrically to either dissipate energy for decelerating the body or to store elastic recoil energy in preparation for a shortening (concentric) contraction. The muscle forces produced during this lengthening behavior can be extremely high, despite the requisite low energetic cost. Traditionally, these high-force eccentric contractions have been associated with a muscle damage response.

Dynamic knee stability after anterior cruciate ligament rupture.

A functional classification scheme has been devised to study knee stabilization strategies after anterior cruciate ligament rupture. A screening examination can determine which patients may be candidates for nonsurgical treatment (potential copers). A rehabilitation program that includes support surface perturbations can improve the potential coper's ability to stabilize the knee.

Specificity of muscle action after anterior cruciate ligament injury.

Neuromuscular control is believed to be a critical factor in dynamic knee stability. The purpose of this study was to evaluate voluntary muscle control in anterior cruciate ligament deficient (ACL-D) and uninjured people. Twenty athletes of similar age participated in this study.

Data-Based Interval Throwing Programs for Collegiate Softball Players.

OBJECTIVE: To construct interval throwing programs followed by a simulated game for collegiate softball players at all positions. The programs are intended to be used as functional progressions within a comprehensive rehabilitation program for an injured athlete or to augment off-season conditioning workouts. DESIGN AND SETTING: We collected data over a single season of National Collegiate Athletic Association softball at the University of Delaware and Goldey Beacom College.

Quadriceps strength and volitional activation before and after total knee arthroplasty for osteoarthritis.

Introduction: Patients with osteoarthritis (OA) of the knee have quadriceps weakness and arthrogenous muscle inhibition (AMI). While total knee arthroplasty (TKA) reliably reduces pain and improves function in patients with knee OA, quadriceps weakness persists after surgery. The purpose of this investigation was to assess contributions of AMI to quadriceps weakness before and after TKA and to assess the effect of pain on AMI.

Voluntary activation and decreased force production of the quadriceps femoris muscle after total knee arthroplasty.

Background And Purpose: Quadriceps femoris muscle weakness as manifested by a decrease in force-generating capability is a persistent problem after total knee arthroplasty (TKA). The authors hypothesized that (1) patients with a TKA would have decreased quadriceps femoris muscle performance (weakness) and impaired volitional activation when compared with a group of older adults without knee pathology, (2) pain and age would account for a large portion of the variability in volitional activation after surgery, and (3) volitional activation in the TKA group would account for a large portion of the variability in force production.

Subjects: Comparison subjects were 52 volunteers (mean age=72.

Are voluntary muscle activation deficits in older adults meaningful?

The relationship between the central activation ratio (CAR) and contraction force is curvilinear, not linear as was previously believed. Voluntary quadriceps femoris muscle activation from previously collected data sets in 46 older adults (64-84 years) and 46 young adults (18-32 years) were therefore reexamined using a curvilinear model of the voluntary muscle activation-percent maximum voluntary force relationship. This method revealed lower voluntary muscle activation in older adults (0.

Predictability of maximum voluntary isometric knee extension force from submaximal contractions in older adults.

The purposes of this study were to develop and test a model describing the relationship between the central activation ratio (CAR; a measure of voluntary muscle activation) and percent maximum voluntary contraction (%MVC) force for old adults and to provide a method for more accurate determination of voluntary muscle activation failure. Twenty-one adults (ages 64-81) performed isometric testing of the quadriceps at 25%, 50%, 75%, and 100% MVC. During each contraction, a 100-HZ, 120-ms train of electrical pulses was delivered to the quadriceps muscle to quantify voluntary muscle activation.

Changes in weight-bearing following injury or surgical reconstruction of the ACL: relationship to quadriceps strength and function.

Purpose: Changes in weight-bearing an average of 1.5 months after ACL injury (ACLD) and up to 3 months after surgical reconstruction (ACLR) were investigated using a force platform. Correlations between force platform test variables, quadriceps strength and functional self-report scores were also examined.

Development of dynamic knee stability after acute ACL injury.

Recently, a training program that includes perturbation of support surfaces has been shown to allow most active individuals with ACL injury who pass a screening examination to successfully return to high level activities. The purpose of this study was to identify the effect of this rehabilitation program on involved side muscle activation during walking in subjects with acute ACL rupture and to determine if the activation changes were coincident with improved function. Nine subjects with an acute, unilateral ACL injury or rupture of an ACL graft, who met the screening examination criteria, received ten sessions of rehabilitation that included perturbation training.

The effect of insufficient quadriceps strength on gait after anterior cruciate ligament reconstruction.

Objective: To determine the effect of quadriceps strength and joint stability on gait patterns after anterior cruciate ligament injury and reconstruction.

Design: Cross-sectional comparative study in which four groups underwent motion analysis with surface electromyography.

Background: Individuals following anterior cruciate ligament rupture often demonstrate reduced knee angles and moments during the early stance phase of gait.

The use of electrical stimulation to increase quadriceps femoris muscle force in an elderly patient following a total knee arthroplasty.

Background And Purpose: Persistent residual quadriceps femoris muscle force deficits after total knee arthroplasty (TKA) are commonly reported and can prevent patients from returning quickly and fully to functional activities. Neuromuscular electrical stimulation offers a potentially more effective means of increasing muscle force than current rehabilitation protocols.

Case Description: The patient was a 66-year-old man.

Dynamic knee stability: current theory and implications for clinicians and scientists.

We will discuss the mechanisms by which dynamic knee stability may be achieved and relate this to issues that interest clinicians and scientists concerned with dynamic knee stability. Emphasis is placed on the neurophysiologic evidence and theory related to neuromuscular control. Specific topics discussed include the ensemble firing of peripheral mechanoreceptors, the potential for muscle stiffness modulation via force and length feedback, postural control synergies, motor programs, and the neural control of gait.

Biomechanical evidence supporting a differential response to acute ACL injury.

Objective: To describe movement patterns in people with complete anterior cruciate ligament rupture objectively identified as good candidates for non-operative management of the injury.

Design: Involved side kinematics and kinetics were compared to the uninvolved side and to uninjured subjects.

Background: High-level athletes with anterior cruciate ligament rupture and poor dynamic stability (non-copers) have movement alterations, including less knee flexion and a decreased internal knee extensor moment during loading response, that are not seen in those with excellent knee stability (copers).

Characterization of the human quadriceps muscle in active elders.

Objective: To compare muscle activation deficits and muscle physiology in older versus younger adults.

Design: A maximal volitional isometric contraction of the quadriceps muscle with burst-superimposition was used to assess strength and activation. In addition, force-frequency testing during fresh, fatigue, and recovery conditions and electrically elicited fatigue testing were performed.

Dynamic stability in the anterior cruciate ligament deficient knee.

Some individuals can stabilize their knees following anterior cruciate ligament rupture even during activities involving cutting and pivoting (copers), others have instability with daily activities (non-copers). Movement and muscle activation patterns of 11 copers, ten non-copers and ten uninjured subjects were studied during walking and jogging. Results indicate that distinct gait adaptations appeared primarily in the non-copers.