Gait analysis of patients with knee osteoarthritis highlights a pathological mechanical pathway and provides a basis for therapeutic interventions

Knee osteoarthritis (OA) is a painful and incapacitating disease affecting a large portion of the elderly population, for which no cure exists. There is a critical need to enhance our understanding of OA pathogenesis, as a means to improve therapeutic options. Knee OA is a complex disease influenced by many factors, including the loading environment. Analysing knee biomechanics during walking - the primary cyclic load-bearing activity - is therefore particularly relevant. There is evidence of meaningful differences in the knee adduction moment, flexion moment and flexion angle during walking between non-OA individuals and patients with medial knee OA. Furthermore, these kinetic and kinematic gait variables have been associated with OA progression. Gait analysis provides the critical information needed to understand the role of ambulatory biomechanics in OA development, and to design therapeutic interventions. Multidisciplinary research is necessary to relate the biomechanical alterations to the structural and biological components of OA. Cite this article: Favre J, Jolles BM. Analysis of gait, knee biomechanics and the physiopathology of knee osteoarthritis in the development of therapeutic interventions. EFORT Open Rev 2016;1:368-374. DOI: 10.1302/2058-5241.1.000051

Walking with shorter stride length could improve knee kinetics of patients with medial knee osteoarthritis.

Walking with a shorter stride length (SL) was recently proposed for gait retraining in medial knee osteoarthritis; however it was never assessed in this patient population. This study tested the hypothesis that shortening SL while maintaining walking speed reduces knee adduction (KAM) and flexion (KFM) moments in patients with medial knee osteoarthritis. Walking trials with normal SL and SL reduced by 0.10 m and 0.15 m were recorded for 15 patients (10 men, 55.5 ± 8.7 years old, 24.6 ± 3.0 kg/m <sup>2</sup> ). SL was modified using an augmented reality system displaying target footprints on the floor. Repeated one-way ANOVAs and post-hoc paired t-tests were performed to compare gait measures between normal and reduced SL. The individual effects of SL reduction were analyzed using descriptive statistics. Group analysis indicated significant decreases in KAM impulse with both SL reductions (p < 0.05). No systematic change was observed in the first peaks KAM and KFM when walking with reduced SL (p > 0.05). Individually, 33 % of the patients decreased the peak KAM, whereas 20 % decreased the KAM impulse. Among these patients with a decrease in peak KAM or in KAM impulse, 0 % and 33 % had a simultaneous increase in peak KFM, respectively. In conclusion, this study showed that SL shortening can decrease kinetic measures associated with the progression of medial knee osteoarthritis in some patients, demonstrating the importance of considering SL modifications on an individual basis. While further research is necessary, notably regarding dose-response relationships and long-term effects, these findings are particularly encouraging because SL reductions could be easily integrated into rehabilitation protocols

A new ambulatory system for comparative evaluation of the three-dimensional knee kinematics, applied to anterior cruciate ligament injuries

The aim of this study was to develop an ambulatory system for the three-dimensional (3D) knee kinematics evaluation, which can be used outside a laboratory during long-term monitoring. In order to show the efficacy of this ambulatory system, knee function was analysed using this system, after an anterior cruciate ligament (ACL) lesion, and after reconstructive surgery. The proposed system was composed of two 3D gyroscopes, fixed on the shank and on the thigh, and a portable data logger for signal recording. The measured parameters were the 3D mean range of motion (ROM) and the healthy knee was used as control. The precision of this system was first assessed using an ultrasound reference system. The repeatability was also estimated. A clinical study was then performed on five unilateral ACL-deficient men (range: 19-36years) prior to, and a year after the surgery. The patients were evaluated with the IKDC score and the kinematics measurements were carried out on a 30m walking trial. The precision in comparison with the reference system was 4.4°, 2.7° and 4.2° for flexion-extension, internal-external rotation, and abduction-adduction, respectively. The repeatability of the results for the three directions was 0.8°, 0.7° and 1.8°. The averaged ROM of the five patients' healthy knee were 70.1° [standard deviation (SD) 5.8°], 24.0° (SD 3.0°) and 12.0° (SD 6.3°) for flexion-extension, internal-external rotation and abduction-adduction before surgery, and 76.5° (SD 4.1°), 21.7° (SD 4.9°) and 10.2° (SD 4.6°) 1year following the reconstruction. The results for the pathologic knee were 64.5° (SD 6.9°), 20.6° (SD 4.0°) and 19.7° (8.2°) during the first evaluation, and 72.3° (SD 2.4°), 25.8° (SD 6.4°) and 12.4° (SD 2.3°) during the second one. The performance of the system enabled us to detect knee function modifications in the sagittal and transverse plane. Prior to the reconstruction, the ROM of the injured knee was lower in flexion-extension and internal-external rotation in comparison with the controlateral knee. One year after the surgery, four patients were classified normal (A) and one almost normal (B), according to the IKDC score, and changes in the kinematics of the five patients remained: lower flexion-extension ROM and higher internal-external rotation ROM in comparison with the controlateral knee. The 3D kinematics was changed after an ACL lesion and remained altered one year after the surger

Spatiotemporal parameters during turning gait maneuvers of different amplitudes in young and elderly healthy adults: A descriptive and comparative study.

Turning during walking adds complexity to gait and has been little investigated until now. Research question What are the differences in spatiotemporal parameters between young and elderly healthy adults performing quarter-turns (90°), half-turns (180°) and full-turns (360°)? The spatiotemporal parameters of 10 young and 10 elderly adults were recorded in a laboratory while turning at 90°, 180° and 360°. Two-way mixed ANOVA were performed to determine the effect of age and turning amplitude. Elderly were slower and needed more steps and time to perform turns of larger amplitude than young adults. Cadence did not differ across age or across turning amplitude. Generally, in the elderly, the spatial parameters were smaller and the temporal parameters enhancing stability (i.e., double-support phase and stance/cycle ratio) were larger, especially for turns of larger amplitudes. In elderly adults, the variability of some spatial parameters was decreased, whereas the variability of some temporal parameters was increased. Stride width of the external leg showed the most substantial difference between groups. Most parameters differed between turning at 90° and turning at larger amplitudes (180°, 360°). Significance This study extends the characterization of turning biomechanics with respect to ageing. It also suggested paying particular attention to the turning amplitude. Finally, the age-related differences may pave the way for new selective rehabilitation protocols in the elderly

Walking with Different Insoles Changes Lower-Limb Biomechanics Globally in Patients with Medial Knee Osteoarthritis.

Using insoles to modify walking biomechanics is of keen interest for the treatment of medial-compartment knee osteoarthritis. So far, insole interventions have focused on reducing the peak of the knee adduction moment (pKAM) and have led to inconsistent clinical outcomes. This study aimed to evaluate the changes in other gait variables related to knee osteoarthritis when patients walk with different insoles to provide insights into the necessity to enlarge the biomechanical analyses to other variables. Walking trials were recorded for 10 patients in four insole conditions. Changes among conditions were computed for six gait variables, including the pKAM. The associations between the changes in pKAM and the changes in the other variables were also assessed individually. Walking with different insoles had noticeable effects on the six gait variables, with high heterogeneity among patients. For all variables, at least 36.67% of the changes were of medium-to-large effect size. The associations with the changes in pKAM varied among variables and patients. In conclusion, this study showed that varying the insole could globally influence ambulatory biomechanics and that limiting measurement to the pKAM could lead to an important loss of information. Beyond the consideration of additional gait variables, this study also encourages personalized interventions to address inter-patient variability

The openness conjecture and complex Brunn-Minkowski inequalities

We discuss recent versions of the Brunn-Minkowski inequality in the complex setting, and use it to prove the openness conjecture of Demailly and Koll\'ar.Comment: This is an account of the results in arXiv:1305.5781 together with some background material. It is based on a lecture given at the Abel symposium in Trondheim, June 2013. 13 page

Experimental study of Taylor's hypothesis in a turbulent soap film

An experimental study of Taylor's hypothesis in a quasi-two-dimensional turbulent soap film is presented. A two probe laser Doppler velocimeter enables a non-intrusive simultaneous measurement of the velocity at spatially separated points. The breakdown of Taylor's hypothesis is quantified using the cross correlation between two points displaced in both space and time; correlation is better than 90% for scales less than the integral scale. A quantitative study of the decorrelation beyond the integral scale is presented, including an analysis of the failure of Taylor's hypothesis using techniques from predictability studies of turbulent flows. Our results are compared with similar studies of 3D turbulence.Comment: 27 pages, + 19 figure

Step by step capping and strain state of GaN/AlN quantum dots studied by grazing incidence diffraction anomalous fine structure

The investigation of small size embedded nanostructures, by a combination of complementary anomalous diffraction techniques, is reported. GaN Quantum Dots (QDs), grown by molecular beam epitaxy in a modified Stranski-Krastanow mode, are studied in terms of strain and local environment, as a function of the AlN cap layer thickness, by means of grazing incidence anomalous diffraction. That is, the X-ray photons energy is tuned across the Ga absorption K-edge which makes diffraction chemically selective. Measurement of \textit{hkl}-scans, close to the AlN (30-30) Bragg reflection, at several energies across the Ga K-edge, allows the extraction of the Ga partial structure factor, from which the in-plane strain of GaN QDs is deduced. From the fixed-Q energy-dependent diffracted intensity spectra, measured for diffraction-selected iso-strain regions corresponding to the average in-plane strain state of the QDs, quantitative information regarding composition and the out-of-plane strain has been obtained. We recover the in-plane and out-of-plane strains in the dots. The comparison to the biaxial elastic strain in a pseudomorphic layer indicates a tendency to an over-strained regime.Comment: submitted to PR