Abstract
Many school children and adolescents experience musculoskeletal pain in the lower extremities. For some
individuals, the pain is persistent and can affect both health and career choices later in life. As
musculoskeletal pain is common already at school age, and since the consequences can be severe, it would
be natural to investigate if any identifiable risk factors precede musculoskeletal pain at this age.
A potential musculoskeletal risk factor is dynamic knee valgus (DKV) that is defined as a medial position of
the knee during dynamic weight-bearing movement. DKV has been investigated in adults and adolescent
populations and is, generally, considered a risk factor for the development of both traumatic and overuse
injuries in the lower extremities. DKV is also known to be more prevalent among females, and some
evidence suggests that this sex-difference accelerates at puberty. Although DKV is well studied in older
ages, it is unknown to what extent DKV is present among children, if there are any sex-differences, and if
there are any associations between early-in-life DKV and musculoskeletal health later in life.
The quantification of DKV requires some form of motion capture. Traditional methods of motion capture
involve the precise attachment of markers onto the skin of the investigated subjects and, therefore, tend
to require long participant preparation times. Furthermore, the attached markers can interfere with the
natural movement patterns of the investigated subject. Therefore, traditional methods of marker-based
motion capture are not feasible for collecting large amounts of data in young children. Marker-less motion
capture is a relatively novel technology that allows motion capture without the use of markers or
anthropometric measurements. This leads to much shorter participant preparation times and allows the
subjects to move naturally without impedance from attached equipment. This technology, therefore, holds
promising feasibility, but the validity is not fully established, especially not in preschool populations.
The overall aim of this thesis was to identify applicable motion capture measures in preschool children,
and use these to create a dataset for future investigations of potential associations between early-in-life
motor patterns and later musculoskeletal health. The specific foci of this thesis are first, to establish and
evaluate the concurrent reliability and agreement between a marker-based and a novel markerless
motion-capture system when measuring kinematics and jump performance in a sample of 14 preschool
children (Study I). Secondly, to establish and evaluate the week-to-week test-retest reliability of selected
kinematics measured in 63 preschool children using the marker-less motion capture system (Study II).
Thirdly, to report the results from a cross-sectional study examining DKV, measured using the marker-less
motion capture system, in a sample of 458 4 to 6-year-old preschool children. Specifically, to report on the
prevalence of DKV, as well as potential differences of DKV concerning sex, age, and motor performance
(Study III). In study I, we found that the measurements of five kinematic variables as well as jump length and height
could be measured with acceptable reliability and agreement by the marker-less motion capture system.
In study II, we found that the week-to-week test-retest reliability of single estimates of the same five
kinematic variables was poor. Our results indicated that high levels of biological variation caused the poor
week-to-week reliability rather than instrumental variability.
In study III, we found that roughly 75% of 4 to 6-year-old children land with some degree of DKV, but also
that girls are twice as common as boys among those children who land with the most pronounced levels of
DKV.
Overall, this research project was successful in creating a dataset containing complete motion capture data
from 604 preschool children. This dataset is valuable for future prospective research projects. The markerless motion capture technology used in this thesis is now at a level of maturity where it is feasible to use in
large scale projects, and where selected kinematic and jump performance measures have demonstrated
acceptable validity in preschool children.
In general, preschool children show high levels of week-to-week variability in their kinematic jump-landing
patterns, although their week-to-week jump-length performance is relatively stable. Roughly 75% of
preschool children land with some level of DKV, and girls are twice as common as boys among those
children with the most extreme values of DKV. More research is needed to clarify the potential relationship
between motor performance and kinematic landing strategies, and whether DKV early in life may interfere
with later musculoskeletal pain or injury.
Original language | English |
---|---|
Supervisors/Advisors |
|
Publication status | Published - 7. Jul 2020 |