Investigation of the biomechanical effect of variable stiffness shoe on external knee adduction moment in various dynamic exercises

Systematic Review of the Role of Footwear Constructions in Running Biomechanics: Implications for Running-Related Injury and Performance

Although the role of shoe constructions on running injury and performance has been widely investigated, systematic reviews on the shoe construction effects on running biomechanics were rarely reported. Therefore, this review focuses on the relevant research studies examining the biomechanical effect of running shoe constructions on reducing running-related injury and optimising performance. Searches of five databases and Footwear Science from January 1994 to September 2018 for related biomechanical studies which investigated running footwear constructions yielded a total of 1260 articles. After duplications were removed and exclusion criteria applied to the titles, abstracts and full text, 63 studies remained and categorised into following constructions: (a) shoe lace, (b) midsole, (c) heel flare, (d) heel-toe drop, (e) minimalist shoes, (f) Masai Barefoot Technologies, (g) heel cup, (h) upper, and (i) bending stiffness. Some running shoe constructions positively affect athletic performance-related and injury-related variables: 1) increasing the stiffness of running shoes at the optimal range can benefit performance-related variables; 2) softer midsoles can reduce impact forces and loading rates; 3) thicker midsoles can provide better cushioning effects and attenuate shock during impacts but may also decrease plantar sensations of a foot; 4) minimalist shoes can improve running economy and increase the cross-sectional area and stiffness of Achilles tendon but it would increase the metatarsophalangeal and ankle joint loading compared to the conventional shoes. While shoe constructions can effectively influence running biomechanics, research on some constructions including shoe lace, heel flare, heel-toe drop, Masai Barefoot Technologies, heel cup, and upper requires further investigation before a viable scientific guideline can be made. Future research is also needed to develop standard testing protocols to determine the optimal stiffness, thickness, and heel-toe drop of running shoes to optimise performance-related variables and prevent running-related injuries.

Wedged Insoles and Gait in Patients with Knee Osteoarthritis: A Biomechanical Review

The study of gait biomechanics in individuals with knee osteoarthritis has become widespread, especially in regards to the knee adduction moment-a variable commonly believed to be associated with knee osteoarthritis progression. Unfortunately, this variable is often studied clinically without considering how it is derived, or what it means in a mechanical context. The use of footwear for knee osteoarthritis management has received much attention as well. However, in many cases, footwear is studied without regard for the mechanical effects they actually induce on the patient. Therefore, this review aims to summarize the current state of knowledge in regards to knee osteoarthritis gait and footwear biomechanics, by taking a step back to review the foundations of these two research areas. First, an overview of the calculation of the knee adduction moment is provided, along with mechanical considerations. Then, this is used to discuss current evidence for wedged insoles and highlight knowledge gaps. The intent was to place this mechanical information in a clinically-oriented framework for approachability by scientists, engineers and clinicians alike. Based on this discussion, areas for future investigation are proposed.

Comparisons of knee and ankle joint angles and ground reaction force according to functional differences during single-leg drop landing

[Purpose] The purpose of this study was to determine potential predictors of functional instability of the knee and ankle joints during single-leg drop landing based on the prior history of injury. [Subjects and Methods] The subjects were 24 collegiate soccer players without pain or dysfunction. To compare the differences between the stable and unstable sides during single-leg drop landing, 8 motion analysis cameras and a force plate were used. The Cortex 4 software was used for a biomechanical analysis of 3 events. An independent t-test was used for statistical comparison between both sides; p<0.05 indicated significance. [Results] The knee joint movements showed gradual flexion in the sagittal plane. The unstable-side ankle joint showed plantar flexion of approximately 2° relative to the stable side. In the coronal plane, the unstable-side knee joint differed from the stable side in its tendency for valgus movement. The unstable-side ankle joint showed contrasting movement compared with the stable side, and the difference was significant. Regarding the vertical ground reaction force, the stable side showed maximum knee flexion that was approximately 0.1 BW lower than that of the unstable side. [Conclusion] Increasing the flexion angle of the knee joint can help prevent injury during landing.

Calculation of external knee adduction moments: a comparison of an inverse dynamics approach and a simplified lever-arm approach

BACKGROUND

The external knee adduction moment (EKAM) is often studied in knee osteoarthritis research. This study compared EKAMs between two methods of calculation: a method that only requires ground reaction force and knee position data (i.e. lever-arm), and an inverse dynamics link-segment method.

METHODS

Sixteen participants walked while wearing a control shoe with and without a six millimeter lateral wedge insole. Peak EKAMs between the lever-arm and inverse dynamics methods were compared for the control condition, and the %change in moment induced by the lateral wedge was compared between methods.

RESULTS

When comparing EKAMs between methods, no correlation was found (r=0.24, p=0.36); peak EKAMs with the lever-arm method (26.0Nm) were significantly lower than EKAMs with the inverse dynamics method (40.2Nm, pb0.001); and Bland-Altman plots showed poor agreement between methods. When assessing the %change in moment with a lateral wedge, a moderate correlation was found (r=0.55, p=0.03) between methods; Bland-Altman plots showed moderate agreement between methods; and the lever-arm method (-6.4%) was not significantly different from the inverse dynamics method (-11.4%, p=0.09); however, the two methods produced opposite results 31% of the time.

CONCLUSION

The lever-arm method cannot estimate peak EKAMs, and can only approximate the %change in moment induced by a lateral wedge; however, the error rate was 31%. Therefore, the lever-arm method is not recommended for use in its current form.

CLINICAL RELEVANCE

This study may help guide the development of a fast and simple method for determining EKAMs for individuals with knee osteoarthritis.