Context: Knee injuries are prevalent, and the associated knee pain is linked to disability. The influence of knee pain on movement biomechanics, independent of other factors related to knee injuries, is difficult to study and unclear.Objective: (1) To evaluate a novel experimental knee-pain model and (2) better understand the independent effects of knee pain on walking and running biomechanics.Design: Crossover study. Setting: Biomechanics laboratory.Patients or Other Participants: Twelve able-bodied volunteers (age ¼ 23 6 3 years, height ¼ 1.73 6 0.09 m, mass ¼ 75 6 14 kg).Intervention(s): Participants walked and ran at 3 time intervals (preinfusion, infusion, and postinfusion) for 3 experimental conditions (control, sham, and pain). During the infusion time interval for the pain and sham conditions, hypertonic or isotonic saline, respectively, was continuously infused into the right infrapatellar fat pad for 22 minutes.Main Outcome Measure(s): We used repeated-measures analyses of variance to evaluate the effects of time and condition on (1) perceived knee pain and (2) key biomechanical characteristics (ground reaction forces, and joint kinematics and kinetics) of walking and running (P , .05).Results: The hypertonic saline infusion (1) increased perceived knee pain throughout the infusion and (2) reduced discrete characteristics of each component of the walking ground reaction force, walking peak plantar-flexion angle (range ¼ 628-678), walking peak plantar-flexion moment (range ¼ 95-104 NÁm), walking peak knee-extension moment (range ¼ 36-49 NÁm), walking peak hip-abduction moment (range ¼ 62-73 NÁm), walking peak support moment (range ¼ 178-207 NÁm), running peak plantar-flexion angle (range ¼ 388-778), and running peak hip-adduction angle (range ¼ 5-218).Conclusions: This novel experimental knee pain model consistently increased perceived pain during various human movements and produced altered running and walking biomechanics that may cause abnormal knee joint-loading patterns.
This review summarises the key points in taking a history and performing a comprehensive clinical examination for patients with foot and/or ankle problems. It is a useful guide for residents who are preparing for their specialty exams, as well as family doctors and any other doctor who has to deal with foot and ankle problems in adults.
Coulomb interactions govern most optoelectronic properties in semiconductors including bandgap, excitons, polaron formation, light absorption, interaction of carriers with defects, charge and energy transport. A clear signature of the strength of many-body Coulomb interactions is the exciton binding energy (Eb). As such, the importance of Eb is perhaps second only to the fundamental band gap (Eg) in understanding the physics and efficiency of low-dimensional semiconductors. However, despite their importance, Eg and Eb are difficult to measure. Here, by choosing 2D halide perovskites as the material and electroabsorption as the experimental probe, we measure Eg and Eb with a precision that is an order of magnitude better than typical methods. The Eb values are both lower than previous literature reports and lower than expected from standard theory. Using dielectric spectroscopy, density functional theory, and quantum mechanical modeling, we demonstrate these low Eb values are a consequence of unique screening effects, such as superlattice screening and phonon screening. We demonstrate a clear correlation between Eb and Eg and provide design principles in order to a priori tune Eg and Eb to their optimal values. As such, this work lays the blueprint for Eg-Eb engineering of low-dimensional semiconductors, as an even more useful replacement to simply band gap engineering.
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