# Single-Leg Squat Performance and Reported Pain within Youth Softball Players
## 4 Discussion  
Based on the fact that the SLS is a reliable assessment of LPHC strength and stability, sport performance, and lower extremity pain [9, 11, 14, 16, 17, 18], the purpose of this study to investigate the associations between bilateral SLS performance and reported pain in youth softball athletes. A positive correlation was found between bilateral differences of knee valgus at maximal knee flexion and pain. Contrary to our hypothesis, greater anterior pelvic tilt, greater ipsilateral pelvic tilt, greater knee valgus, and less sacrum displacement were not correlated with reported pain. However, these variables did have a near significant correlation with reported pain and should be discussed due to possible clinical significance. The present study found no significant relationships between pain and SLS pelvic kinematics in the descent phase of each leg. Both greater dynamic anterior pelvic tilt during the left SLS descent phase and greater ipsilateral pelvic tilt during the right SLS descent reared a significant correlation with reported pain. These results are supported by previous findings indicating relationships between SLS, LPHC kinematics, and pain [22, 23]. Specifically, it has been found that those with patellofemoral pain had increased ipsilateral trunk lean, contralateral pelvic drop, and hip adduction [22, 23], and found females with pain had greater hip internal rotation [22]. Additionally, it has been found that female patients with lower extremity injury displayed greater internal hip rotation, less knee flexion, and more trunk flexion on their injured compared to their noninjured leg [23]. Although the present study did not include trunk or hip kinematics, the increase in pelvic lateral tilt in the right SLS among those with pain is a strong indicator of increased internal hip rotation, while the increase in anterior pelvic tilt in the left SLS is a strong indicator of trunk flexion. The present study also found a near significant correlation between greater degrees of knee valgus and reported pain at maximal knee flexion, 45\({}^{\circ}\) ascent (left SLS), and during the descent phase (left SLS and right SLS). These findings are also supported by previous reports of increased knee valgus while performing the SLS in patients with patellofemoral pain [22, 24]. Additionally, increased knee valgus during the SLS has been classified as 'poor performance' and a risk for injury [25]. The near significant correlations between vertical sacrum displacement and pain in the right SLS at maximal knee flexion and 45\({}^{\circ}\) ascent disagree with our hypothesis. Those participants who squatted down further, as measured by their vertical sacrum displacement from a neutral stance, were more likely to experience pain. It is possible that athletes who achieved greater sacrum displacement did so due to lack of eccentric control during the decent phase, meaning these participants may not have the \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Kinematic Variable**} & \multicolumn{2}{c}{**Pain**} \\ \hline  & **Left SLS** & **Right SLS** \\ \hline
**Knee Valgus/Varus** & & \\ Descent Phase & 0.270 (0.083) \(\char 10^{\circ}\) & 0.292 (0.060) \(\char 10^{\circ}\) \\ Ascent Phase & 0.152 (0.336) & 0.214 (0.173) \\ \hline
**Sacrum Displacement** & & \\ Descent Phase & 0.128 (0.420) & 0.160 (0.311) \\ Ascent Phase & \(-\)0.101 (0.526) & \(-\)0.145 (0.360) \\ \hline
**Anterior/Posterior Pelvic Tilt** & & \\ Descent Phase & \(-\)0.259 (0.097) \(\char 10^{\circ}\) & \(-\)0.157 (0.322) \\ Ascent Phase & 0.048 (0.762) & 0.101 (0.525) \\ \hline
**Lateral Pelvic Tilt** & & \\ Descent Phase & \(-\)0.120 (0.451) & 0.267 (0.088) \(\char 10^{\circ}\) \\ Ascent Phase & \(-\)0.106 (0.502) & \(-\)0.190 (0.229) \\ \hline \hline \end{tabular} \({}^{*}\) denotes a significant correlation \(p<0.05\); \({}^{*}\) denotes a near significant correlation \(p<0.10\); \(p\)-values are located in parenthesis.  
\end{table}