|dc.description.abstract||Adolescent girls are susceptible to knee injuries such as non-contact anterior cruciate ligament (ACL) rupture and patellofemoral pain (PFP). Adolescence is synonymous with pubertal development which drives substantial growth and maturation of the musculoskeletal system, and is thought to contribute to poor knee biomechanics associated with both of these injuries. Specifically, higher tri-planar knee moments during puberty (external peak knee abduction moment (KAbM), flexion moment (KFM) and internal rotation moment (KIRM)) are thought to contribute to a higher incidence of these injuries; however, there are still gaps in our understanding of female pubertal biomechanics. For instance, variations in dynamic tasks (i.e., bilateral vs single limb), unreliable pubertal classification methods, small sample sizes, conflicting findings and data normalisation methods (i.e., mixed between body mass or body mass by height) highlight the need for additional, better designed pubertal studies.
The role of athletic footwear is also an important consideration, given it may alter tri-planar knee moments relevant to both non-contact ACL rupture or PFP. Specifically, high-support footwear is thought to control excessive foot pronation, which may transfer up the kinetic chain and confer protection at the proximal knee joint by modifying tri-planar knee moments during dynamic tasks. By contrast, low-support shoes do not possess the same stability features, potentially allowing for greater foot pronation that may have a clinically meaningful effect on tri-planar knee moments compared to high-support shoes. Surprisingly, no studies have explored the effects of these shoes during female pubertal development, which is concerning as many adolescent girls are likely wearing these types of shoes during the various sports in which the aforementioned knee injuries occur.
To address the current limitations in pubertal and footwear biomechanical research, four cross-sectional studies are reported in this thesis. Ninety-three girls aged between 7-25 years old were categorised into three key stages of puberty: pre-pubertal (n = 31, mean age = 9.4 ± 1.2), early/mid-pubertal (n = 31, mean age = 11.1 ± 1.4) and late/post-pubertal (n = 31, mean age = 19.8 ± 4.0). Tri-planar knee moments normalised to body mass (Nm/kg) and body mass by height (Nm/kg/m) were analysed across landing and running-related tasks in each pubertal group. These were initially observed barefoot, and then subsequently, the effect of high- and low-support footwear was explored across both tasks.
The primary aim of Study 1 was to determine whether peak tri-planar knee moments differed between three stages of female pubertal development during a barefoot single limb drop lateral jumping (DLJ) task. The secondary aim was to explore the hip adduction moment (HAM) at time of peak KAbM and the hip flexion moment (HFM) at time of peak KFM between pubertal groups. In the frontal plane, a higher peak KAbM was found for the late/post- compared to the pre-pubertal group when normalised to body mass (95%CI=-0.02 to -0.17 Nm/kg, p=0.015, d=0.61), but not body mass by height (p=0.88). At the hip, neither body mass or body mass by height normalised data revealed between-group differences for HAM at time of peak KAbM (p>0.05). In the sagittal plane, a higher peak body mass-normalised KFM was found for the late/post- (95%CI=0.19 to 0.68 Nm/kg, p=0.001, d=1.12) and the early/mid-pubertal groups compared to the pre-pubertal group (95%CI=0.05 to 0.52 Nm/kg, p=0.017, d=0.59). No significant between-group differences were found for body mass by height-normalised peak KFM (p=0.30) or the HFM at time of peak KFM (p>0.05). Finally, in the transverse plane, a higher peak KIRM in the late/post- compared to both the early/mid- (95% CI = -0.09, -0.01 Nm/kg, p=0.028, d=0.62) and pre-pubertal groups (95% CI= -0.12, -0.03 Nm/kg, p=0.001, d=0.82) was found for body mass, but not body mass by height normalised data.
The primary aim of Study 2 was to determine whether peak tri-planar knee moments differed across footwear conditions (i.e., barefoot, high-support and low-support shoes) during the single-limb DLJ amongst late/post-pubertal girls. Based on the findings in Study 1, the late/post-pubertal group was selected as they displayed higher mass normalised tri-planar knee moments compared to early/mid- and pre-pubertal counterparts and may be at higher risk of ACL injury. Results revealed no significant differences for peak KAbM or KIRM regardless of statistical adjustment for FPI (p>0.05). By contrast, peak KFM was higher in the high-support (95% CI= 0.36, 0.53 Nm/kg, p<0.001, d= 1.11) and low-support shoes (95% CI= 0.25, 0.48 Nm/kg, p<0.001, d= 0.85) compared to barefoot; however, no significant differences were observed between shoe conditions. Together, Study 1 and 2 provide novel insights into the effects of female puberty and footwear on the biomechanics of single-limb landing, revealing that increased pubertal-related height (i.e., stature), rather than body mass, is the main contributor to augmented tri-planar knee moments in the latter stages of female pubertal development, which athletic footwear did not ameliorate.
The primary aim of Study 3 was to examine tri-planar knee moments (normalised to body mass and body mass by height) across the three pubertal stages while running barefoot. Higher peak body mass-normalised KFM was apparent in the late/post-pubertal (95% CI= 0.18 to 0.63 Nm/kg, p=0.001, d= 1.01) and early/mid-pubertal (95% CI= 0.02, 0.47 Nm/kg, p=0.034, d=0.52) girls compared to the pre-pubertal girls; however, no significant differences were found when KFM was normalised to body mass by height (p>0.05). Furthermore, no significant differences were found for body mass or body mass by height normalised peak KAbM or KIRM (p>0.05). At the hip, a lower body mass normalised HAM at time of peak KFM (i.e., greater hip abduction moments) was found in the late/post- (95% CI= -0.51, -0.11 Nm/kg, p=0.003, d= 0.86) and early/mid-pubertal (95% CI= -0.42, -0.01 Nm/kg, p=0.039, d= 0.53) girls compared to their pre-pubertal counterparts. Likewise, in the sagittal plane a decrease in body mass normalised HFM at time of peak KFM was evident with the late/post-pubertal girls displaying lower HFM (95% CI= 0.65, 0.28 Nm/kg, p<0.001, d=1.27) compared to their early/mid- and pre-pubertal counterparts (95% CI= 0.36, 0.73 Nm/kg, p<0.001, d=1.42).
Study 4 determined whether footwear conditions (i.e., barefoot, high-support, low-support) effect running-related peak KFM amongst a pooled sample of early/mid- and late/post-pubertal girls. Based on the findings in Study 3, girls in the early/mid- and late/post-pubertal groups were pooled as no differences in body mass normalised tri-planar knee moments were observed; however, they both displayed higher peak KFM compared to pre-pubertal girls. The secondary aim explored predictors associated with a change in the peak KFM wearing shoes compared to barefoot (i.e., knee-ground reaction force (GRF) lever arm, sagittal plane resultant GRF magnitude and sagittal plane lower limb kinematics) to help elucidate the underlying biomechanical mechanism. A main effect (p<0.001) for peak KFM was found, revealing both high- (95% CI= 0.36, 0.49 Nm/kg, p<0.001, d=1.07) and low-support (95% CI= 0.31, 0.45 Nm/kg, p<0.001, d=0.97) footwear increased peak KFM compared to barefoot, no differences were found between shoes (p>0.05). The regression models identified that only a change in the knee-GRF lever arm in shoes compared to barefoot was associated with a change in peak KFM (F(1, 109)= 93.56, p<0.001), but not the sagittal plane GRF magnitude or any lower limb kinematics (p>0.05). Combined, Study 3 and 4 provide evidence for a developmental increase in sagittal plane but not frontal or transverse plane knee moments that are likely attributed to differences in adolescent height while running. More importantly, wearing shoes increased peak KFM even further regardless of whether they possessed supportive characteristics, and this was partly driven by an increase in the knee-GRF lever arm. Given the repetitive and chronic loading pattern associated with the development of adolescent PFP, both puberty and athletic footwear may influence the manifestation of this condition.
Further studies are required to prospectively determine whether higher body mass landing-related tri-planar knee moments and running-related peak KFM in the later stages of puberty are indeed linked to ACL rupture or PFP, respectively. Moreover, pubertal footwear studies may consider modifying footwear features to determine if these higher knee moments can be attenuated.||en_US