Lean muscle volume of the thigh has a stronger relationship with muscle power than muscle strength in women with knee osteoarthritis

BackgroundThigh lean muscle and intramuscular fat have been implicated in the impairment of physical function observed in people with knee osteoarthritis. We investigated the relationships of quadriceps and hamstrings intramuscular fat fraction and lean muscle volume with muscle power and strength, controlling for neuromuscular activation, and physical performance in women with knee OA.MethodsWomen (n = 20) 55 years or older with symptomatic, radiographic knee osteoarthritis underwent a 3.0T magnetic resonance imaging scan of the thigh of their most symptomatic knee. Axial fat-separated images were analyzed using software to quantify intramuscular fat and lean muscle volumes of the quadriceps and hamstrings. To quantify strength and power of the knee extensors and flexors, participants performed maximum voluntary isometric contraction and isotonic knee extensions and flexions, respectively. Electromyography of the quadriceps and hamstrings was measured. Participants also completed five physical performance tests.FindingsQuadriceps and hamstrings lean muscle volumes were related to isotonic knee extensor (B = 0.624; p = 0.017) and flexor (B = 1.518; p = 0.032) power, but not knee extensor (B = 0.001; p = 0.615) or flexor (B = 0.001; p = 0.564) isometric strength. Intramuscular fat fractions were not related to isotonic knee extensor or flexor power, nor isometric strength. No relationships were found between intramuscular fat or lean muscle volume and physical performance.InterpretationMuscle power may be more sensitive than strength to lean muscle mass in women with knee osteoarthritis. Thigh lean muscle mass, but neither intramuscular nor intermuscular fat, is related to knee extensor and flexor power in women with knee osteoarthritis.     

A sex comparison of reactive knee stiffness regulation strategies under cognitive loads

BackgroundSex differences may exist in cognitive faculties and neuromuscular strategies for maintaining joint stability. The purpose of this study was to assess whether preparatory and reactive knee stiffening strategies are affected differently in males and females exposed to sex-biased cognitive loads.Methods20 male and 20 female volunteers were tested for knee joint stiffness and quadriceps and hamstring muscle activation patterns throughout a rapid eccentric knee extension perturbation. Participants were tested under 3 cognitive loads (Benton's Judgment of Line Orientation; Symbol Digit modalities Test; and Serial 7's) and a control condition. Apparent knee joint stiffness and muscle activation amplitude and timing were quantified throughout the perturbation across the 4 conditions.FindingsReactive knee stiffness values were significantly less during the cognitive tasks compared to the control condition (Judgment of Line Orientation = 0.034 Nm/deg/kg, Symbol Digit Modalities Test = 0.037 Nm/deg/kg, Serial 7's = 0.037 Nm/deg/kg, control = 0.048 Nm/deg/kg). Females had greater normalized total apparent stiffness than males. The quadriceps muscles had faster and greater activation than the hamstring muscles; however, no group differences were observed. No overall differences in muscle activation (magnitude and timing) were found between the cognitive loading tasks.InterpretationCognitive loading may decrease the ability of healthy individuals to reactively stiffen their knee joint and appears to interfere with the normal stiffness regulation strategies. This may elucidate an extrinsic risk factor for non-contact knee ligament injury.     

Mechanical behavior of fixation components for periprosthetic fracture surgery

BackgroundReliable periprosthetic fracture treatment needs detailed knowledge on the mechanical behavior of the fixation components used. The holding capacity of three conventional fixation components for periprosthetic fracture treatment was systematically investigated under different loading directions.MethodsLocking compression plates were fixed to a 7 cm long part of diaphyseal fresh frozen human femur with either a single 1.7 mm cerclage cable, a 5.0 mm monocortical or a bicortical locking screw (n = 5 per group). Constructs were loaded in lateral, torsional and axial direction with respect to the bone axis in a load-to-failure test. Corresponding stress distribution around the screw holes was analyzed by finite element modeling.FindingsBoth screw fixations revealed significantly higher stiffness and ultimate strength in axial compression and torsion compared to the cerclage (all P < 0.01). Ultimate strength in lateral loading and torsion was significantly higher for bicortical screws (mean 3968 N SD 657; mean 28.8 Nm SD 5.9) compared to monocortical screws (mean 2748 N SD 585; mean 14.4 Nm SD 5.7 Nm) and cerclages (mean 3001 N SD 252; mean 3.2 Nm SD 2.0) (P ≤ 0.04). Stress distribution around the screw hole varied according to the screw type and load direction.InterpretationFixation components may be combined according to their individual advantages to achieve an optimal periprosthetic fracture fixation.     

The role of knee joint moments and knee impairments on self-reported knee pain during gait in patients with knee osteoarthritis

BackgroundThe association between high mechanical knee joint loading during gait with onset and progression of knee osteoarthritis has been extensively studied. However, less attention has been given to risk factors related to increased pain during gait. The purpose of this study was to evaluate knee joint moments and clinical characteristics that may be associated with gait-related knee pain in patients with knee osteoarthritis.MethodsSixty-seven participants with knee osteoarthritis were stratified into three groups of no pain (n = 18), mild pain (n = 27), or moderate/severe pain (n = 22) based on their self-reported symptoms during gait. All participants underwent three-dimensional gait analysis. Quadriceps strength, knee extension range of motion, radiographic knee alignment and self-reported measures of global pain and function were also quantified.FindingsThe moderate/severe pain group demonstrated worse global pain (P < 0.01) and physical function scores (P < 0.01) compared to the no pain and the mild pain groups. The moderate/severe pain group also walked with greater knee flexion moments during the midstance phase of gait compared to the no pain group (P = 0.02). Additionally, the moderate/severe pain group demonstrated greater varus knee malalignment (P = 0.009), which was associated with higher weight acceptance peak knee adduction moments (P = 0.003) and worse global pain (P = 0.003) and physical function scores (P = 0.006).InterpretationGreater knee flexion moment is present during the midstance phase of gait in patients with knee osteoarthritis and moderate/severe pain during gait. Additionally, greater varus malalignment may be a sign of increased global knee joint dysfunction that can influence many activities of daily living beyond gait.     

Isokinetic strength differences between patients with primary reverse and total shoulder prostheses: Muscle strength quantified with a dynamometer

BackgroundRange of motion after total shoulder arthroplasty is better than after reverse shoulder arthroplasty, however with similar clinical outcome. It is unclear if this difference can only be found in the different range of motion or also in the force generating capacity. Questions: (1) are isokinetically produced joint torques of reverse shoulder arthroplasty comparable to those of total shoulder arthroplasty? (2) Does this force-generating capacity correlate with functional outcome?MethodsEighteen reverse shoulder arthroplasty patients (71 years (SD 9 years)) (21 shoulders, follow-up of 21 months (SD 10 months)) were recruited, 12 total shoulder arthroplasty patients (69 years (SD 9 years)) (14 shoulders, follow-up of 35 months (SD 11 months)). Pre- and post-operative Constant–Murley scores were obtained; two isokinetic protocols (ab-/adduction and ex-/internal rotations) at 60°/s were performed.FindingsTwelve of 18 reverse shoulder arthroplasty patients generated enough speed to perform the test (13 shoulders). Mean ab-/adduction torques are 16.3 Nm (SD 5.6 Nm) and 20.4 Nm (SD 11.8 Nm). All total shoulder arthroplasty patients generated enough speed (14 shoulders). Mean ab-/adduction torques are 32.1 Nm (SD 13.3 Nm) and 43.1 Nm (SD 21.5 Nm). Only 8 reverse shoulder arthroplasty patients (9 shoulders) could perform ex-/internal rotation tasks and all total shoulder arthroplasty patients. Mean ex-/internal rotation torques are 9.3 Nm (SD 4.7 Nm) and 9.2 Nm (SD 2.1 Nm) for reverse shoulder arthroplasty, and 17.9 Nm (SD 7.7 Nm) and 23.5 Nm (SD 10.6 Nm) for total shoulder arthroplasty. Significant correlations between sub-scores: activity, mobility and strength and external rotation torques for reverse shoulder arthroplasty. Moderate to strong correlation for sub-scores: strength in relation to abduction, adduction and internal rotation torques for total shoulder arthroplasty.InterpretationShoulders with a total shoulder arthroplasty are stronger. This can be explained by the absence of rotator cuff muscles and (probably) medialized center of rotation in reverse shoulder arthroplasty. The strong correlation between external rotation torques and post-operative Constant–Murley sub-scores demonstrates that external rotation is essential for good clinical functioning in reverse shoulder arthroplasty.     

Local vibration training improves the recovery of quadriceps strength in early rehabilitation after anterior cruciate ligament reconstruction: A feasibility randomised controlled trial

BackgroundAfter anterior cruciate ligament reconstruction (ACLR), quadriceps strength must be maximised as early as possible.ObjectivesWe tested whether local vibration training (LVT) during the early post-ACLR period (i.e., ～10 weeks) could improve strength recovery.MethodsThis was a multicentric, open, parallel-group, randomised controlled trial. Thirty individuals attending ACLR were randomised by use of a dedicated Web application to 2 groups: vibration (standardised rehabilitation plus LVT, n = 16) or control (standardised rehabilitation alone, n = 14). Experimenters, physiotherapists and participants were not blinded. Both groups received 24 sessions of standardised rehabilitation over ～10 weeks. In addition, the vibration group received 1 hour of vibration applied to the relaxed quadriceps of the injured leg at the end of each rehabilitation session. The primary outcome — maximal isometric strength of both injured and non-injured legs (i.e., allowing for limb asymmetry measurement) — was evaluated before ACLR (PRE) and after the 10-week rehabilitation (POST).ResultsSeven participants were lost to follow-up, so data for 23 participants were used in the complete-case analysis. For the injured leg, the mean (SD) decrease in maximal strength from PRE to POST was significantly lower for the vibration than control group (n = 11, ?16% [10] vs. n = 12, ?30% [11]; P = 0.0045, Cohen's d effect size = 1.33). Mean PRE–POST change in limb symmetry was lower for the vibration than control group (?19% [11] vs. ?29% [13]) but not significantly (P = 0.051, Cohen's d effect size = 0.85).ConclusionLVT improved strength recovery after ACLR. This feasibility study suggests that LVT applied to relaxed muscles is a promising modality of vibration therapy that could be implemented early in ACLR.Trial registrationClinicalTrials.gov: NCT02929004.     

Augmented screws in angular stable plating of the proximal humerus: What to do when revision is needed?

BackgroundBone cement augmentation of modified cannulated locking screws shows biomechanically and clinically good results for osteoporotic fracture management. Nevertheless, complications need to be considered. Therefore implant removal should be tested for feasibility.MethodsImplant removal was simulated in 7 pairs of osteoporotic cadaveric humeri: During screw removal from an angular stable proximal humerus plate, we measured the maximum torque of 14 augmented screws and the corresponding 14 non-augmented screws on the contralateral humeri. After screw removal, specimens were cut along the screw axes to macroscopically investigate the impact of screw removal on the surrounding bone. In addition, we established a technique for cement removal in cases in which the screw head is obstructed with cement and therefore disables the insertion of the screwdriver.FindingsThe screw extraction torque measurements showed no significant differences between the two groups regarding one screw (screw 4 augmented: 1.52 Nm, SD 0.25 Nm vs. screw 4 non-augmented: 1.80 Nm, SD 0.40 Nm; P = 0.20), whereas torque values for the second screw in the augmented group were lower than in the control group (screw 5 augmented: 0.72 Nm, 0.31 Nm vs. screw 5 non-augmented: 1.42 Nm, 0.52 Nm; P = 0.009). Macroscopy of the bone showed no damage to the trabeculae within the humeral head due to the removal.InterpretationThe removal of cannulated, polymethylmethacrylate-augmented, 2.8 mm titanium screws from an angular stable plate was uncomplicated, without the need for special instruments or increased torque for screw removal. No additional damage was visible at the bone-cement interface.     

Ankle strength impairments associated with knee osteoarthritis

BackgroundKnee Osteoarthritis seems to negatively impact ankle biomechanics. However, the effect of knee osteoarthritis on ankle muscle strength has not been clearly established. This study aimed to evaluate the ankle strength of the plantar flexors and dorsiflexors of patients with knee osteoarthritis in different degrees of severity.MethodsThirty-seven patients with knee osteoarthritis and 15 controls, subjected to clinical and radiographic analysis, were divided into three groups: control, mild, and moderate knee osteoarthritis. Participants answered a self-reported questionnaire and accomplished a muscle torque assessment of the ankle using the Biodex dynamometer in isometric, concentric and eccentric modes.FindingsThe mild osteoarthritis group (peak torque = 26.85(SD 3.58)) was significantly weaker than the control (peak torque = 41.75(SD 4.42)) in concentric plantar flexion (P < 0.05). The control and mild osteoarthritis groups were not significantly different from the moderate osteoarthritis group (peak torque = 36.12(SD 4.61)) in concentric plantar flexion. There were no significant differences for dorsiflexion among the groups; however the control and moderate osteoarthritis groups presented large and medium standardized mean differences. The mild osteoarthritis group was significantly lower than the control and moderate osteoarthritis groups in the concentric plantar flexion by concentric dorsiflexion torque ratio.InterpretationAnkle function exhibited impairments in patients with knee osteoarthritis, especially in the plantar flexion torque, in which the mild osteoarthritis group was weaker than the control. Interestingly, patients with moderate knee osteoarthritis showed results similar to the control group in plantar flexion torque. The results raise the possibility of a compensatory mechanism of the plantar flexors developed by patients in more advanced degrees to balance other muscle failures.     

Effects of a home-based rehabilitation program in obese type 2 diabetics

ObjectiveTo assess, in obese type 2 diabetics (T2D), the impact of a home-based effort training program and the barriers to physical activity (PA) practice.MethodTwenty-three obese T2D patients (52.7 ± 8.2 years, BMI = 38.5 ± 7.6 kg/m²) were randomized to either a control group (CG), or an intervention group (IG) performing home-based cyclergometer training during 3 months, 30 min/day, with a monthly-supervised session. The initial and final measurements included: maximal graded effort test on cyclergometer, 6-minute walk test (6MWT) and 200-meter fast walk test (200mFWT), quadriceps maximal isometric strength, blood tests and quality of life assessment (SF- 36). A long-term assessment of the amount of physical activity (PA) and the barriers to PA practice was conducted using a questionnaire by phone call.ResultsPatients in the CG significantly improved the maximal power developed at the peak of the cyclergometer effort test (P < 0.05) as well as the quadriceps strength (P < 0.01). There were no significant changes in the other physical and biological parameters, neither in quality of life. At a mean distance of 17 ± 6.4 months, the PA score remained low in the two groups. The main barriers to PA practice identified in both groups were the perception of a low exercise capacity and a poor tolerance to effort, lack of motivation, and the existence of pain associated to PA.ConclusionThis home-based intervention had a positive impact on biometrics and physical ability in the short term in obese T2D patients, but limited effects in the long term. The questionnaires completed at a distance suggest considering educational strategies to increase the motivation and compliance of these patients.     

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction

BackgroundThe purpose of this study was to determine associations between self-reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction.MethodsForty-one individuals [31% male, BMI mean 25 (SD 4) kg/m², months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self-reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0–100 ms (early), 100–200 ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self-reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength.FindingsHigher rate of torque development 100–200 ms is weakly associated with higher self-reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r = 0.274, p = 0.091); however, rate of torque development 100–200 ms does not predict a significant amount of variance in self-reported function after accounting for strength (ΔR² = 0.003, P = 0.721).InterpretationQuadriceps strength has a greater influence on self-reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery.     

Effect of gender on strength gains after isometric exercise coupled with electromyographic biofeedback in knee osteoarthritis: A preliminary study

ObjectiveThe objective of this trial was to evaluate the effect of gender on strength gains after five week training programme that consisted of isometric exercise coupled with electromyographic biofeedback to the quadriceps muscle.Materials and methodsForty-three (20 men and 23 women) patients with knee osteoarthritis (OA), were placed into two groups based on their gender. Both groups performed isometric exercise coupled with electromyographic biofeedback for five days a week for five weeks.ResultsBoth groups reported gains in muscle strength after five week training. However, the difference was found to be statistically insignificant between the two groups (P = 0.224).ConclusionThe results suggest that gender did not affect gains in muscle strength by isometric exercise coupled with electromyographic biofeedback in patients with knee OA.     

Effects of a low-intensity dynamic-resistance training protocol using an isokinetic dynamometer on muscular strength and aerobic capacity after coronary artery bypass grafting

ObjectiveStudy the effect of muscle strength training on muscle strength, maximal oxygen uptake (VO₂max), hemodynamic and anthropometric parameters as well as quality of life after coronary artery bypass grafting (CABG).MethodsAfter CABG surgery, 32 patients were randomized into two groups. The first group was to perform aerobic-type training with a cycle ergometer (AT = 16). The second group was to perform low-intensity muscle strength training of the quadriceps and hamstrings using an isokinetic dynamometer (i.e. 20 to 30% of peak torque) (ST = 16). Before and after the strength training program we conducted a stress test, evaluation of isokinetic force production, 6-minute walking test, body impedance analysis (BIA) and SF-36 quality of life test.ResultsCompared to the AT group, the ST group showed better results with improved quadriceps strength (48.2% vs. 8.2%), VO₂max (P < .001) and diastolic blood pressure at rest (P = 0.01). Quality of life improved in both groups.ConclusionThe dynamic-resistance muscle strength training protocol using isokinetic dynamometer can safely (i.e. without clinical symptoms or changes to the ECG and arterial blood pressure) improve muscle strength and VO₂max without any major risks in patients post-CABG. These findings should encourage additional studies to validate the relevance of these strength training modalities in rehabilitation centers.     

Neuromuscular rate of force development deficit in Parkinson disease

BackgroundBradykinesia and reduced neuromuscular force exist in Parkinson disease. The interpolated twitch technique has been used to evaluate central versus peripheral manifestations of neuromuscular strength in healthy, aging, and athletic populations, as well as moderate to advanced Parkinson disease, but this method has not been used in mild Parkinson disease. This study aimed to evaluate quadriceps femoris rate of force development and quantify potential central and peripheral activation deficits in individuals with Parkinson disease.MethodsNine persons with mild Parkinson Disease (Hoehn & Yahr ≤ 2, Unified Parkinson Disease Rating Scale total score = mean 19.1 (SD 5.0)) and eight age-matched controls were recruited in a cross-sectional investigation. Quadriceps femoris voluntary and stimulated maximal force and rate of force development were evaluated using the interpolated twitch technique.FindingsThirteen participants satisfactorily completed the protocol. Individuals with early Parkinson disease (n = 7) had significantly slower voluntary rate of force development (p = 0.008; d = 1.97) and rate of force development ratio (p = 0.004; d = 2.18) than controls (n = 6). No significant differences were found between groups for all other variables.InterpretationsPersons with mild-to-moderate Parkinson disease display disparities in rate of force development, even without deficits in maximal force. The inability to produce force at a rate comparable to controls is likely a downstream effect of central dysfunction of the motor pathway in Parkinson disease.     

Upper torso pain and musculoskeletal structure and function in women with and without large breasts: A cross sectional study

BackgroundWomen with large breasts frequently experience upper torso pain secondary to their breast size. Evidence is lacking on the underlying causes of this pain. This study investigated whether upper torso pain and musculoskeletal structure and function differed between women with large breasts and women with small breasts.MethodsA linear regression, adjusting for body mass, compared the upper torso pain, thoracic flexion torque due to breast mass, thoracic kyphosis, shoulder active range-of-motion, and scapular retraction muscle strength of 27 women with large breasts (bilateral breast volume > 1200 ml, age 45.9 y SD 9.9 y, BMI 29.0 kg/m² SD 3.8 kg/m²) and 26 women with small breasts (bilateral breast volume < 800 ml, age 43.8 y SD10.9 y, BMI 23.3 kg/m² SD 2.9 kg/m²).FindingsWomen with large breasts reported a higher upper torso pain score (46.6, 95%CI 33.3–58.0 versus 24.1, 95%CI 12.5–37.8), accompanied by a larger flexion torque (5.9 Nm, 95%CI 4.5–5.8 Nm versus 0.9 Nm, 95%CI 0.8–2.4 Nm), greater thoracic kyphosis (34°, 95%CI 31–38° versus 27°, 95% CI 24–31°), decreased shoulder elevation range-of-motion (160°, 95%CI 158–163° versus 169°, 95%CI 166–172°), and decreased scapular retraction endurance-strength (511.4 s, 95%CI 362.2–691.3 s versus 875.8 s, 95%CI 691.5–1028.4 s) compared to the women with small breasts.InterpretationDifferences in the upper torso posture, range-of-motion, and muscle strength of women with large breasts provides insight into underlying causes of their musculoskeletal pain. This information can be used to develop evidence-based assessment and treatment strategies to relieve and prevent symptom progression.     

The role of muscle strength & activation patterns in patellofemoral pain

BackgroundTo investigate the extent to which quadriceps muscle activation and strength are responsible for patellofemoral pain.MethodsA pain on–off switch system synchronized with a force transducer and surface electromyography was utilized on 32 volunteer patellofemoral pain patients during maximal isometric and squat exercises.FindingsThere were 26 patients out of the 32 tested who complained of pain during the squat or isometric test, of these 20 subjects presented a significant advantage for the vastus lateralis compared to the vastus medialis obliquis activation and 12 patients had decreased quadriceps strength of the symptomatic compared to the non symptomatic leg. All patients who demonstrated weak vastus medialis obliquis activation during the isometric exercise possessed the same symptoms during the squat. On the other hand, 9 patients who showed diminished vastus medialis obliquis activation during the squat displayed equal activation between the vastus medialis obliquis and the vastus lateralis during the isometric task. With regard to the timing for the onset of muscle activation, there were only 4 patients who had a difference (P = 0.03) between the symptomatic (0.042 s) and non-symptomatic legs (0.011 s).InterpretationCauses for patellofemoral pain vary and are not necessarily a result of quadriceps strength deficit or vastus medialis obliquis activation weakness. Patellofemoral pain patients who possess lower vastus medialis obliquis activation compared to the vastus lateralis do not necessarily have quadriceps weakness while patients presenting with quadriceps strength deficits do not always have an imbalance between vastus medialis obliquis and vastus lateralis activation.     

Crenobalneotherapy (spa therapy) in patients with knee and generalized osteoarthritis: A post-hoc subgroup analysis of a large multicentre randomized trial

ObjectiveTo determine whether the addition of spa therapy to home exercises provides any benefit over exercises and the usual treatment alone in the management of generalised osteoarthritis associated with knee osteoarthritis.MethodsThis study was a post-hoc subgroup analysis of our randomised multicentre trial (www.clinicaltrial.gov: NCT00348777). Participants who met the inclusion criteria of generalized osteoarthritis (Kellgren, American College of Rheumatology, or Dougados criteria) were extracted from the original randomised controlled trial. They had been randomised using Zelen randomisation. The treatment group received 18 days of spa treatment in addition to a home exercise programme. Main outcome was number of patients achieving minimal clinically important improvement at six months (MCII) (≥ −19.9 mm on the VAS pain scale and/or ≥ −9.1 points in a WOMAC function subscale), and no knee surgery. Secondary outcomes included the “patient acceptable symptom state” (PASS) defined as VAS pain ≤ 32.3 mm and/or WOMAC function subscale ≤ 31 points.ResultsFrom the original 462 participants, 214 patients could be categorized as having generalised osteoarthritis. At sixth month, 182 (88 in control and 94 in SA group) patients, were analysed for the main criteria. MCII was observed more often in the spa group (n = 52/94 vs. 38/88, P = 0.010). There was no difference for the PASS (n = 19/88 vs. 26/94, P = 0.343).ConclusionsThis study indicates that spa therapy with home exercises may be superior to home exercise alone in the management of patients with GOA associated with knee OA.     

Kinematic and kinetic gait deviations in males long after anterior cruciate ligament reconstruction

BackgroundBiomechanical deviations long (approx. 5 years) after anterior cruciate ligament reconstruction have not been quantified in males, despite their distinct risk profile as compared to females. These deviations can indicate altered joint loading during chronic, repetitive motions.MethodsCross-sectional study, comparing kinematic and kinetic variables between 15 male anterior cruciate ligament reconstructed patients and 15 healthy controls. During walking and running gait, measurements were taken of impact dynamics, knee and hip sagittal plane angles and moments, and knee varus angles and adduction moments.FindingsComparing affected limbs to control limbs, significantly lower maximum (P = 0.001) and initial (P = 0.003) loading rates were found during running, but not in walking. Hip angles were lower for affected limbs of patients compared to the control group (P = 0.039) in walking, but not during running. Between-limb comparisons showed important differences in symmetry of the affected patients. Maximum force during running was higher in the unaffected limb (P = 0.015), which was linked with a higher loading rate (P = 0.008). Knee flexion angle was reduced by 2° on average for the affected limb during running (P = 0.010), and both walking and running knee and hip moments showed differences. Knee varus angle showed a 1° difference during walking (P < 0.001), but not during running. Knee adduction moment was significantly lower (more valgus) during both walking and running.InterpretationMale anterior cruciate ligament reconstructed patients demonstrate persistent, clinically important gait asymmetries and differences from healthy controls long after surgery in kinematics, kinetics, and impact biomechanics.     

Difference in the running biomechanics between preschoolers and adults

BackgroundHigh vertical loading rate is associated with a variety of running-related musculoskeletal injuries. There is evidence supporting that non-rearfoot footstrike pattern, greater cadence, and shorter stride length may reduce the vertical loading rate. These features appear to be common among preschoolers, who seem to experience lower running injury incidence, leading to a debate whether adults should accordingly modify their running form.ObjectiveThis study sought to compare the running biomechanics between preschoolers and adults.MethodsTen preschoolers (4.2 ± 1.6 years) and ten adults (35.1 ± 9.5 years) were recruited and ran overground with their usual shoes at a self-selected speed. Vertical average (VALR) and vertical instantaneous loading rate (VILR) were calculated based on the kinetic data. Footstrike pattern and spatiotemporal parameters were collected using a motion capture system.ResultsThere was no difference in normalized VALR (p = 0.48), VILR (p = 0.48), running speed (p = 0.85), and footstrike pattern (p = 0.29) between the two groups. Preschoolers demonstrated greater cadence (p < 0.001) and shorter normalized stride length (p = 0.01).ConclusionBy comparing the kinetic and kinematic parameters between children and adults, our findings do not support the notion that adults should modify their running biomechanics according to the running characteristics in preschoolers for a lower injury risk.     

Sex-specific hip osteoarthritis-associated gait abnormalities: Alterations in dynamic hip abductor function differ in men and women

BackgroundHip osteoarthritis results in abnormal gait mechanics, but it is not known whether abnormalities are the same in men and women. The hypothesis tested was that gait abnormalities are different in men and women with hip osteoarthritis vs. sex-specific asymptomatic groups.Methods150 subjects with mild through severe radiographic hip osteoarthritis and 159 asymptomatic subjects were identified from an Institutional Review Board-approved motion analysis data repository. Sagittal plane hip range of motion and peak external moments about the hip, in all three planes, averaged from normal speed walking trials, were compared for men and women, with and without hip osteoarthritis using analysis of variance.FindingsThere were significant sex by group interactions for the external peak hip adduction and external rotation moments (P = 0.009–0.045). Although asymptomatic women had peak adduction and external rotation moments that were respectively 12% higher and 23% lower than asymptomatic men (P = 0.026–0.037), these variables did not differ between men and women with hip osteoarthritis (P ≥ 0.684). The osteoarthritis vs. asymptomatic group difference in the peak hip adduction moment was 45% larger in women than in men. The osteoarthritis vs. asymptomatic group difference in the peak hip external rotation moment was 55% larger for men than for women (P < 0.001). Sex did not influence the association between radiographic severity and gait variables.InterpretationNormal sex differences in gait were not seen in hip osteoarthritis. Sex-specific adaptations may reflect different aspects of hip abductor function. Men and women with hip osteoarthritis may require different interventions to improve function.