Lower Extremity Biomechanics

BACKGROUND: Altered lower limb movement patterns (LLMP) during the forward step down (FSD) test have been studied in people suffering from knee instability. However, ankle dorsiflexion range of motion (ADROM) seems to be related to LLMP but no causal inference has been defined between those variables. OBJECTIVE: Our goals were to evaluate (1) psychometric quality of the FSD test in healthy people and (2) the influence of experimental restricted ADROM on LLMP. METHODS: Kinematics were measured by a motion capture system. Angular displacement and speed were calculated as well as center of mass (COM) and knee linear displacement. Forty-two healthy participants; firstly, performed the test three times to assess reliability, and secondly the same test in an experimental condition limiting the ADROM. RESULTS: Reliability was excellent for all parameters (ICC: 0.75-0.99, SEM%: 2.0-34.0%). ADROM limitation significantly decreased Knee flexion range of motion (ROM) (−3.8 •), increased Hip flexion ROM (6 •), Hip adduction ROM (6.1 •), Pelvis drop ROM (3.5 •), Pelvic rotation ROM (3.1 •). No significant effect was found for Hip rotation ROM. CONCLUSIONS: LLMP was affected by this experimental ADROM limitation in healthy people. As this limitation is often encountered in post-traumatic ankle sprain patients, clinicians should consider this point during FSD assessment test.

Anterior cruciate ligament (ACL) rupture is a serious and debilitating injury that usually results in an athlete undergoing reconstructive surgery and remaining out of sport for an extended period.  Therefore the incidence of this injury although only moderate (approximately one per professional Australian football team per year) when considered from a social and sporting cost perspectives is of serious concern.  However, the non-contact nature of the majority of occurrences of this injury indicates that it may be possible to reduce the incidence with interventions aimed at modifying the movement and/or physical characteristics of individual athletes.  Previous research aimed at reducing the risk of non-contact ACL injury has focused on improving support of general knee loads, particularly valgus and internal rotation moments, which are known to load the ACL, during sporting tasks through the utilisation of balance and plyometric training.  While technique cues have been included in a number of these training programs there has been no research that has investigated training to change isolated aspects of sidestep cutting and landing techniques and their effect on valgus and internal rotation moments at the knee, the moments thought to cause non-contact ACL injury.  This was the overarching theme of this thesis.

Most non-contact ACL injuries occur during either sidestep cutting or landing tasks, as such, the relationship between technique and knee loads was investigated within these two tasks.  The first study presented in this thesis investigated how performing sidestep cuts with various extreme postures affected knee moments.  It was identified that peak valgus loads during the weight acceptance phase of the sidestep cut were increased when performed with either increased torso lean over the support leg or wide placement of the support leg.  Wide foot placement also resulted in increase peak internal rotation moments.  Sidestep cuts, with torso rotation towards the support leg also increased peak knee internal rotation moments.  As these postures were reflective of those observed during actual non-contact ACL injuries it was concluded that these three postures should be avoided when performing a sidestep cut.
The next study investigated the effectiveness of a six week technique modification program aimed at avoiding the three high loading techniques, identified in the first study, for reducing knee moments during sidestep cutting.  Following the intervention participants performed the sidestep cut with a foot placement closer to the midline of the body and a more upright torso.  These kinematic changes were accompanied by a reduction in the peak valgus moment occurring during the weight acceptance phase of the sidestep cut.  This intervention may then reduce at least one factor identified as being a risk for an athlete of sustaining a non-contact ACL injury.

Studies three and four investigated the relationship between technique and knee loads during landing tasks.  The first of these two studies investigated the effect of ball positioning in a functional landing task on both full body kinematics and knee moments.  When participants were required to take possession of a ball during flight that was swinging towards their support leg they demonstrated increased valgus moments compared with when the ball was swung away from the support leg.  The whole body segmental kinematics of the high loading ball movement reflected body postures observed when injury occurs in a game situation.  However, the high loading task exhibited a more flexed knee posture, contrary to the results expected from the literature.  The second of these two studies further investigated the relationship between whole body kinematics and knee moments. Intra-participant correlations were performed between all kinematics and each knee joint moment, with the intention of identifying mean correlations significantly different from zero.  Increased valgus moments were significantly correlated with increased knee flexion, hip flexion, torso lean and torso rotation towards the support leg, and foot and knee external rotation. Increase internal rotation moments were significantly correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.  Again these results reflected joint positions observed in injury, except for knee flexion and hip flexion angles.  It was identified that while there may be statistically significant effects for knee angle the difference in magnitude may not result in functional differences.

The final study investigated the effect of a six week technique modification program on landing tasks.  The technique modification aimed at bringing athletes’ torsos upright and forward facing, based upon the results of the previous studies.  It also aimed to increase knee flexion angle, as this is still the current literature recommendation.  Post-intervention participants displayed an increase in maximal knee flexion angles but no change in torso positioning.  This kinematic change was correlated to a significant increase in peak internal rotation moments, with no change in valgus or flexion moments.  Although, due to the angle at which the peak internal rotation moment occurred it was identified that this increase in moment may not increase the risk of non-contact ACL injury risk, due to the increased potential for muscular support and decreased transmission of the moment to the ACL.  However, it was concluded that the technique modification program may not be appropriate for reducing the risk of non-contact ACL injury, within the particular landing task chosen.

Overall this thesis identified that whole body kinematics are related to knee moments during sidestep cutting and landing.  Kinematics associated with increase valgus and internal rotation moments at the knee tended to reflect joint posture observed during actual non-contact ACL injuries.  Secondly a six week technique modification program is capable of modifying both sidestep cutting and landing technique.  Technique changes result in changed knee moments.  However, the complex nature of the relationship between technique and knee loads indicates that any potential intervention aimed at reducing the risk of non-contact ACL injury, should be tested in the laboratory utilising tools such as neuromuscular modelling and stochastic modelling to ensure the planned intervention has the potential to be successful prior to implementing the protocol in an epidemiological testing scenario.

"The fibula has rarely been considered in comparative morphological studies, probably due to its relatively minor role in carrying mechanical loads. However, some differences in morphology (and inferred function) of the fibula between humans and apes, and within apes, have been noted and related to differences in positional behavior. Therefore, the study of tibiofibular relations may be useful in characterizing such differences. This study examines cross-sectional geometric (CSG) properties (cortical area and polar section modulus, Zp) of the tibia and fibula at mid-diaphysis across a sample (n ¼ 87) of humans, chimpanzees, gorillas, orangutans, and gibbons. The fibula is compared against the tibia in the different taxa. The results indicate that the robusticity of the fibula relative to that of the tibia can be explained in terms of differences in positional behavior. In particular, hominoids that are more arboreal (i.e., gibbons, orangutans, and chimpanzees) possess a relatively more robust fibula than do hominoids that are more terrestrial (i.e., gorillas and humans). The difference appears to be a consequence of the more mobile fibula and more adducted position of the hindlimb necessary in an arboreal environment. Apart from providing the first CSG data on the fibula,
these results may be helpful in reconstructing the locomotor behavior of fossil hominoids."

Ever since it was first observed and especially so in recent years, the phenomenon of the so-called "sticking point'" in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking the sticking point is understood as the position in the range-of-motion of a lift at which a disproportionately large increase in the difficulty to continue the lift is experienced. Hence the sticking point is inherently the performance bottleneck and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it, is of pervasive importance to strength practitioners and instrumental for the avoidance of injury and continued progress. In this paper we survey a range of physiological and biomechanical mechanisms which contribute to the development of sticking points, and led by this insight review and analyse the findings of the existing observational research on the occurrence of sticking points in three ubiquitous exercises: the bench press, the squat, and the deadlift. The findings of our analysis should be used to inform future research and current resistance training practice.

The purpose of this Series of Case Studies was to determine if the frontal plane position of the cranial bones and atlas could be altered using dental orthotics, prescriptive insoles, or both concurrently.
Methods: The cranial radiographs of four patients were reviewed in this study.  Three of the patients were diagnosed as having a TMJ dysfunction and a PreClinical Clubfoot Deformity.  The fourth patient was diagnosed as having a TMJ dysfunction, a PreClinical Clubfoot Deformity and a Class II Sacral Occipital Subluxation.
Each patient had a series of 4 cranial radiographs taken using a modified orthogonal protocol.  The first cranial radiograph was taken with the patient using neither the dental orthotic nor proprioceptive insoles were used (baseline measurement).  The second cranial radiograph was taken with the patient using only the dental orthotic.  The third cranial radiograph was taken with the patient only using the proprioceptive insoles.  The final cranial radiograph was taken with the patient using both the dental orthotic and proprioceptive insoles concurrently.
The degree of change in angle between the various specified cranial landmarks and atlas were measured directly off of these radiographs and compared to one another.
Results: In two patients, improvement towards orthogonal was achieved when using both prescriptive dental orthotics and prescriptive insole concurrently.  Improvement towards orthogonal was less apparent when using only the prescriptive dental orthotic.  And no improvement or a negative frontal plane shift was noted when using only the prescriptive proprioceptive insoles.
In the third patient, the frontal plane position of the cranial bones and atlas increased (away from orthogonal) when using the generic proprioceptive insoles alone or in combination with a prescriptive dental orthotic.
In the fourth patient, the frontal plane position of the cranial bones improved using the dental orthotic.  However, the proprioceptive insoles when used alone, or in combination with the dental orthotic, increased the frontal plane position of the cranial bones and atlas.
Conclusion:  This study demonstrates that changes in the frontal plane position of the cranial and atlas bones can occur when using proprioceptive insoles and/or dental orthotics.

An abnormal foot structure is described in which the 1st metatarsal is structurally elevated and inverted relative to the 2nd metatarsal.  This foot structure is termed Primus Metatarsus Supinatus (aka Rothbarts Foot).
Embryological studies suggest that this foot structure is the end result of a failed or incomplete unwinding of the talar head.
Clinically, the 1st metatarsal and hallux are off the ground when the standing foot is placed into its anatomical neutral position.
This foot structure is biomechanically dysfunctional, demarcated by its prolonged mid-stance hyperpronation.  Global postural distortions are linked to this foot structure, including:
(1)  anterior rotation of the innominates
(2)  unleveling of the pelvis
(3)  augmenting of the scoliotic and kyphotic spinal curves
(4)  shoulder protraction
(5)  forward head position
(6)  malocclusion
This postural shift is termed Bio-Implosion.

Previous research on the transition from hunting and gathering to production economy has suggested some general trends in past populations, i.e. decreased diaphyseal robusticity, increased cross-sectional circularity and decreased sexual dimorphism in the lower limb bones (femur and tibia), generally explained as a consequence of decreased levels of mobility. Previous results from the study of the Ligurian Neolithic populations from North-Western Italy (6th millennium BP) provide an exception to these trends. In particular, the Ligurian Neolithic lower limb robusticity and diaphyseal shape reflect high levels of terrestrial mobility throughout a rugged terrain. These results argue in favour of the growing consensus that the Neolithic transition was a region-specific process. In this work we expand the sample to include remains from caves from the same area, all within the same pastoral system, and extend the analysis to include the fibula. These new results show that the diaphyseal morphology of the Ligurian sample is more similar to highly mobile European Late Upper Palaeolithic and Mesolithic populations. Furthermore, the degree of sexual dimorphism for mechanical properties indicates behavioural differences between sexes, with males being more mobile than females. The results found here also indicate that inclusion of the fibula may contribute to a better understanding of past population mobility especially when it is considered in association with the tibia.

"This study investigates the relationships between lower limb robusticity and mobility in a Neolithic sample (LIG) from Italy (6th millennium BP). This study tests the hypothesis that the high femoral robusticity previously observed in the LIG sample is a consequence of the subsistence strategy (i.e., high mobility on uneven terrain) practiced by LIG. Cross-sectional geometric properties of the femur and tibia at midshaft of
LIG (eight males and eight females) were collected and
results compared to Late Upper Paleolithic (12 males,
five females), Mesolithic (24 males, 8 females), and Eneolithic
(28 males, 17 females) samples from other sites throughout Europe. The results show that the LIG sample does not show the reduction of lower limb robusticity that is characteristic of the Eneolithic sample, but rather that the LIG sample is most similar to the earlier, highly mobile, populations. This high level of robusticity in the LIG sample could reflect both their pastoral subsistence strategy combined with a rugged environment, as well as their earlier temporal position within the Neolithic. The results of this study further point to significant variation in male-female mobility patterns in the region, also possibly related to pastoral behavioral patterns."

"This paper investigates the changes in upper and lower limb robusticity and activity patterns that accompanied the transition to a Neolithic subsistence in western Liguria (Italy). Diaphyseal robusticity measures were obtained from cross-sectional geometric properties of the humerus and femur in a sample of 16 individuals (eight males and eight females) dated to about 6,000–5,500 BP. Comparisons with European Late Upper Paleolithics (LUP) indicate increased humeral robusticity in Neolithic Ligurian (NEOL) males, but not in females, with
a significant reduction in right-left differences in both
sexes. Sexual dimorphism in robusticity increases in upper and lower limb bones. Regarding the femur, while all female indicators of bending strength decrease steadily through time, values for NEOL males approach those of LUP. This suggests high, and unexpected, levels of mechanical stress for NEOL males, probably reflecting the effects of the mountainous terrain on lower limb remodeling.
Comparisons between NEOL males and a small sample
of LUP hunter-gatherers from the same area support
this interpretation. In conclusion, cross-sectional geometry
data indicate that the transition to Neolithic economies
in western Liguria did not reduce functional requirements
in males, and suggest a marked sexual division of labor involving a more symmetrical use of the upper limb, and different male-female levels of locomotory stress. When articulated with archaeological, faunal, paleopathological, and ethnographic evidence, these results support the hypothesis of repetitive, bimanual use of axes tied to pastoral activities in males, and of more sedentary tasks
linked to agriculture in females."

Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee moments that load the ACL. This study examined whether landing technique training alters knee moments. Nineteen team sport athletes completed the study. Motion analysis and ground reaction forces were recorded before and after 6 weeks of technique modification. An inverse dynamic model was used to calculate three-dimensional knee loading. Pre- and postintervention scores were compared using paired t tests. Maximal knee flexion angle during landing was increased following training. There was no change in valgus or flexion moments, but an increase in peak internal rotation moment. This increase in internal rotation moment may increase the risk of ACL injury. However, the increased angle at which the peak internal rotation moment occurred at follow up may mitigate any increase in injury risk by reducing load transmission.

"Since bone reacts to imposed loads by formation and resorption of tissue, analyses of tissue distribution within a bone provides evidence of the adaptation of that bone to a given mechanical function. Definition of these structure-function relationships allows the physical anthropologist to clarify the wide variety of behavioural/morphological adaptations in extant primates. Structural analysis of primate
limb bones using engineering beam theory can be really useful in reducing complex biological forms to a few readily interpretable and functionally relevant parameters. In the past, several methods of analysing these structural parameters have been described, such as computed tomography, multiple plane radiography, and automated digital analysis. The application of the above techniques to problems in primate adaptation
and evolution includes estimation of body mass in fossil specimens, investigation of relative fore- and hind-limb mechanical loadings, and study of within and between species differences in behaviour (for example locomotion) as reflected in variations of limb bone shape. Cross-sectional geometric properties (areas, second moments of area) have been extensively used for reconstructing the mechanical loading history of long bone shafts. Here we present a study of the biomechanical characteristics performed on cheiridia
and the tibio-fibular complex of extant Hominoidea. Systematic comparison of the structural properties of these bones has not yet been carried out. The results put in evidence the usefulness of cross-sectional geometry in pointing out links between structural properties of long bones and locomotion behaviour in primates, and may be useful in elucidating locomotor adaptations of fossil specimens."

Since it was first observed, and especially so in recent years, the phenomenon of the so-called "sticking point" in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking, the sticking point is understood as the position in the range of motion of a lift at which a disproportionately large increase in the difficulty associated with continuing the lift is experienced. Hence the sticking point is inherently the performance bottleneck, and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it is of pervasive importance to strength practitioners, and is conducive to injury avoidance and continued progress. In this paper, we survey a range of physiological and biomechanical mechanisms which...

Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task.
Methods: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments.
Findings: Landing after an overhead catch when the ball moved towards a player’s support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.
Interpretation: Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete’s risk of non-contact anterior cruciate ligament injury.

The paper discusses common misconceptions regarding Mortons and Rothbarts Foot (listed below):

1) Mortons Foot and Rothbarts Foot are two very similar and/or same foot structure.
2)  Both foot structures are common
3)  Both cause pain in the entire body
4)  Treatment is the same for both foot structures
5)  The same type of proprioceptive insole is used to treat both foot structures

Pressure plate analysis is used to collect surface area (sA) and media pressure (mP) readings on 17 Primus Metatarsus Supinatus Patients.  All 17 patients are fitted with medial column foot insoles. Two sets of surface area (X) and media pressure (Y) readings are recorded on each patients:  A baseline set before treatment and a second set after treatment.
The observed changes in surface area and media pressure are statistically correlated.
The results:
(1) The probability that these patterns are randomized events (based on chance alone) is exceeding small (p >. 01)
(2) There is a high level of confidence that postural tonicity shifts towards homeostasis when insole therapy is effective.
Summation:  From a clinical point of view, these observed changes in surface area and medial pressure readings may prove useful in prognosticating the appropriateness of insole therapy.

This research study investigates the possible link between abnormal foot pronation and the development of abnormal curves in the spinal cord.
  A Study I published in 2006 (Journal of the American Podiatric Medical Association) statistically linked unleveling of the pelvis, which forms the base of the spine, to abnormal foot pronation.  From these findings I extended my research into the entire spine.
  The outcome of this study suggests that the development of scoliosis is linked to abnormal foot pronation.  It is based on a preliminary study of 25 teenage patients with asymmetrical abnormal pronation patterns and a positive Adams Tests.
  Findings:  A positive statistical correlation was found between:
(1)  The pronation pattern
(2)  The pelvic distortion pattern
(3)  The pattern of frontal plane deviation within the thoracic spine