# Incorporation of Torsion Springs in a Knee Exoskeleton for Stance Phase Correction of Crouch Gait
## 4 Discussion  
Crouch gaits vary widely based on the causal injury or pathology, making gait patterns difficult to define. For example, crouch gaits may be caused in individuals with cerebral palsy, which in and of itself has numerous subclassifications, depending on the area of the brain impacted, as well as how extensive the hemiplegic, paraplegic, or quadriplegic damage is. Additional causes include traumatic brain injury, stroke, and other neurological problems, as well as bone deformities. Correction may involve numerous treatment plans, including corrective orthotic devices and/or surgery. One problem with surgical treatment is that in many cases, the outcome is unknown as to whether or not the gait will improve [31]. One common surgical technique is the lengthening of hamstrings, which may improve certain aspects of gait, such as in the knee or ankle; however, surgical treatment has the potential to cause additional problems [8]. [PERSON] et al. helped to define gait patterns in those with spastic hemiplegia that were placed into four separate groups. Comparisons with joints angles in the ankles, knees, and hips, and common symptoms, differentiated between the groups. When comparing these graphs with the knee angles produced in each crouch gait produced in OpenSim, only crouch gaits 3 and 4 contained similarities between two of the groups in [PERSON] assessments. In these cases, the optimum improvement came with surgical procedures for lengthening the hamstrings. In many cases, even after surgery, the results of hamstring \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Minimum Moments** & \begin{tabular}{c} **Torsion** \\ **Springs 20 k** \\ **Nmm/Deg** \\ \end{tabular} & \begin{tabular}{c} **\%Gait** \\ **Cycle** \\ \end{tabular} & \begin{tabular}{c} **Motorized** \\ **Correction 20** \\ **k Nmm/Deg** \\ \end{tabular} & \begin{tabular}{c} **\%Gait** \\ **Cycle** \\ \end{tabular} & \begin{tabular}{c} **Torsion** \\ **Springs 30 k** \\ **Nmm/Deg** \\ \end{tabular} & \begin{tabular}{c} **\%Gait** \\ **Cycle** \\ \end{tabular} & \
\begin{tabular}{c} **Motorized** \\ **Correction 30** \\ **k Nmm/Deg** \\ \end{tabular} &
\begin{tabular}{c} **\%Gait** \\ **Cycle** \\ \end{tabular} \\ \hline CG1 & 103,800.8 & 60 & 42,931.9 & 40 & 179,830.6 & 60 & 44,058.2 & 40 \\ \hline CG2 & 106,115.8 & 36 & 42,701.4 & 40 & 127,834 & 36 & 43,828.5 & 40 \\ \hline CG3 & 72,958.89 & 52 & 40,303.2 & 40 & 103,772.2 & 52 & 41,439.1 & 40 \\ \hline CG4 & 75,131.99 & 40 & 40,535.92 & 40 & 105,117.9 & 40 & 41,670.9 & 40 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Moment minima taken from simulations for each crouch gait. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Normal Gait** & **Maximum Moment** & **\%Gait** & **Minimum Moment** & **\%Gait** & **\%Gait** \\ \hline  & 212,194.5 & 14 & 177,850.8 & 40 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Moment maximum, minimum, and their corresponding percentage occurrences within the normal gait cycle. lengthening were inconsistent or did not work at all [14]. The incorporation of the torsional spring was able to counter the excessive flexion moments produced [32] by applying the stored energy from knee flexion to provide the necessary knee extension [33]. While these results are promising, torsion springs alone do not provide enough correction. With the passive elements alone, the reduction in moment was one component of correction; however, we saw that there needed to be a shift in the occurrence of the peak moments. There was no improvement in CG1 overall, while CG3 still had peak moments occurring at 20% and 52%. CG2 and CG4 benefitted the most from the passive elements because peak moment occurred at 12% for both CG2 and CG4, and 36% and 40%, respectively, in the gait cycle. These gaits either did not change or were near to that of the normal gait before and after motorized angular correction.