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Introduction to Clinical Biomechanics

• Biomechanics involves describing, analyzing, and assessing human movement in sports.
• It includes kinematics (visible movement), kinetics (forces driving movement), and neuromotor aspects (muscle function controlling forces).

Focus on Kinematics

• Subjective biomechanical analysis involves visual observation of movements like running or squatting.
• Clinicians use this approach to assess and treat patients, with or without video analysis or lab equipment.
• Biomechanical evaluation should be completed based on task specificity to ensure accuracy.

Aims of This Chapter

• Outline the basics of 'ideal' lower limb biomechanics
• Explain 'ideal' biomechanics during running
• Describe lower limb biomechanical assessment in the clinical setting
• Outline how to conduct clinical footwear assessments
• Review evidence linking biomechanical factors to injuries and discuss technical factors contributing to specific injuries
• Discuss how to manage detected biomechanical abnormalities
• Explain both normal and abnormal upper limb biomechanics

Ideal Lower Limb Biomechanics – The Basics

• Discusses ideal structural characteristics, including available joint range of motion and stance position.
• Individuals have unique mechanical make-ups due to structural (anatomical) characteristics
• They may never achieve the 'ideal'.

Lower Limb Joint Motion: Hip Joint

• Formed by the femoral head and acetabulum
• Ball-and-socket structure allows motion in all three planes.

Lower Limb Joint Motion: Knee Joint

• Formed by the tibial plateau and femoral condyles
• Primarily a hinge joint
• Allows flexion and extension in the sagittal plane as primary movements
• Permits some rotation in the transverse plane for stance stability and shock absorption

Lower Limb Joint Motion: Ankle Joint

• Located between the shank and rearfoot
• Composed of the talocrual and subtalar joints (STJ)
• The talocrual joint, formed by the talus and the mortise of the tibia and fibula malleoli, allows dorsiflexion and plantarflexion in the sagittal plane
• Motion axis is predominantly in the frontal plane

Subtalar Joint (STJ)

• Formed between the calcaneus and talus
• Articular facets allow for complex triplanar motions of pronation and supination
• During pronation, the STJ axis enables primarily eversion (combined with dorsiflexion and abduction)
• During supination the STJ axis facilitates inversion (combined with plantarflexion and adduction).
• STJ motion axis runs posteriorly and inferiorly with inclination of 40-50° in the sagittal plane, and laterally with inclination of 20-25° in the transverse plane

Midtarsal Joint

• Formed between the midfoot and rearfoot (calcaneocuboid and talonavicular joints)
• The oblique axis allows sagittal plane (dorsiflexion/plantarflexion) and transverse plane (abduction/adduction) motion
• The longitudinal axis allows primarily frontal plane motion.
• Axes orientation allows foot to change role during weight-bearing.
• As rear foot everts, axes align and unlock foot in order to conform to surface and absorb ground reaction force (GRF)
• As rear foot inverts, axes converge and locks foot, creating a rigid lever for propulsion

Midtarsal (Lisfranc) Joints

• Located between the distal tarsal bones (cuneiforms and cuboid) of the midfoot and the five metatarsal bones of the forefoot.
• Axis of motion is primarily in the transverse plane
• Leads to the sagittal plane motion (flexion/extension)
• Some frontal plane motion occurs (eversion/inversion)

First Metatarsophalangeal Joint (MTPJ)

• Formed between the head of the first metatarsal and the base of the proximal phalanx
• Primary sagittal plane motion (flexion/extension)
• Extension is essential for windlass mechanism during gait.

Ideal Neutral Stance

• Requires a normal posture with symmetrically aligned lower limb joints and feet during weight-bearing
• Weight-bearing line runs through the anterior superior iliac spine, patella, and second metatarsal
• Subtalar joint is neither pronated or supinated
• Midtarsal joint is maximally pronated
• First and second metatarsal heads are in contact with ground
• Forefoot's long axis is perpendicular to heel bisection, aligning with the tibial tuberosity
• Ankle joint is neither plantarflexed nor dorsiflexed; tibia is perpendicular
• Knee is fully extended in slight valgus; hips are neutral
• Pelvis is level with slight anterior tilt

Ideal Biomechanics with Movement – Running

• Suboptimal lower limb biomechanics can be associated with many overuse injuries
• Requires assessing lower limb biomechanics during running (focus on heel strike)
• Ideal walking biomechanics are similar to heel strike running patterns

Running vs. Walking

• Airborne/float phase is what distinguishes running from walking
• Vertical ground reaction forces (GRFs) are doubled during running
• Greater anterior pelvic tilt
• Increased sagittal plane excursion of the knee and hip increases stress on structures of lower limb

Heel Strike Pattern of Running

• Divided into phases.

Heel strike to foot flat (loading)

• Leg swings towards the line of progression
• Foot with slight inversion (0-5°) makes contact with the ground
• The pelvis is level, with a slight anterior 10° tilt and internal rotation
• Hip is rotated externally 5-10° and flexed 20-30°
• Knee flexed 10°
• Cascade of events occurs to assist shock absorption due to the laterally directed GRF produced by heel strike
• Rearfoot begins to evert
• Tibial and femoral (hip) internal rotation with hip adduction occurs
• Knee flexion peaks at 45
• Motions are controlled by eccentric muscle activity
• Contralateral pelvic drop should be minimal (~5°)
• Gluteal muscles control motion and dissipate GRF
• Initial rearfoot eversion also results in more parallel alignment of the midtarsal joints and facilitates unlocking
• Forefoot makes solid contact with the ground at foot flat
• Foot adapts during loading to various terrains
• Although motions comprising foot pronation are normal, they should not be excessive or rapid

Excessive Motion/Hyperpronation during loading

• Places strain on structures
• Includes plantar fascia, tibialis posterior muscle, and intrinsic foot musculature
• Increases medial ground reaction force (GRF).
• Accentuation of proximal motion at the knee, hip, and pelvis, increasing load on associated ligamentous and muscular structures.
• Excessive contralateral pelvis drop and/or hip adduction/internal rotation may increase strain
• Structures include the iliotibial band (ITB), gluteal musculature, and tensor fascia latae (TFL) muscle
• May increase load on lumbar spine, tibiofemoral joint, patellofemoral joint (PFJ)

Excessive Anterior Tilting of the Pelvis

• May place excessive strain on the lumbar spine and/or hamstring musculature
• May impair gluteal function
• Inadequate pronation/excessive supination leads to an excessive/prolonged laterally directed GRF.
• Results in a less mobile foot in addition to poor shock absorption
• Associated with lower limb stress fractures
• May increase the incidence of lateral ankle sprain and chronic ankle instability

Midstance (Foot Flat to Heel Off)

• Indicated by forefoot contacting ground in neutral transverse plane
• Requires transition from shock absorption following loading, to biomechanics for propulsion
• The ankle moves towards maximal dorsiflexion (approximately 20°) to enable the tibia and the center of mass (COM) to move over the stance leg
• Excessive ankle dorsiflexion causes increased strain
• Includes the plantar fascia, Achilles tendon, and associated gastrocnemius aSoleus musculature
• The hip/knee moves from flexion towards extension
• Assists with forward motion of the body's COM
• Followed immediately by maximal ankle dorsiflexion Maximal foot pronation
• Reach immediately after the body’s COM has passed anterior to the stance limb.
• Tibia and femur rotate externally Assisted by the force transmission from the externally-rotating pelvis.

Clinician considerations

• Excessive pronation results in too much strain on the plantar fascia, Achilles, and tibialis posterior tendons.
• Continued instability may result in first MTPJ abnormalities including hallux valgus, sesamoid pain, excessive interdigital compression = Morton’s neuroma.
• Excessive/prolonged pronation produces abnormal motions at the hip and knee which can affect structures such as the patellofemoral joint, patellar tendon, and ITB.

Propulsion after heel off

• Foot continues to supinate
• Inversion of rear foot locks with the transfer of joint axes to converge with the midfoot.
• Concurrently
• the stance limb rotates externally, the hip extends
• 0-10° knee flexes due to hamstring contraction Acceleration occurs by plantar flexion at the ankle which is made by gastrocnemius and soleus complex.
• Passively foot’s rigidity occurs by increasing tension on plantar fascia as it pull the calcaneus and metatarsal heads together Hind foot reaches 10° of inversion and forefoot to ~5° of abduction by toe off.

Impaired Propulsion

• Peroneal muscles forced to stabilize medial and lateral foot columns May cause peroneal tendonapthy and stress fracture of the fibula.
• Impaired supination leads to toe off via the lateral forefoot rays instead of first ray Compression of the transverse arch of the foot can lead to interdigital nerve compressions and lateral forefoot fracture.
• Reduce propulsion may lean too much to swing phase
• hip flexors are affected

Initial Swing

• Body enters the first float phase after ipsilateral toe off
• Hamstring and rectus femurs muscle maintain forward momentum

Terminal Swing

• Limb advances and pelvis move with it by abducting and internally rotating hip, which the adductors then control
• Anterior tibialis contracts to engage dorsiflexion

Angle and Base of Gai

• The long axis at the foot and the line of progression determine the angle of gait with ~10° of gait from the progression/direction of movement with walking
• The medial and lateral aspects of the heel determine the base of the foot
• Increases in speed causes the angle and base of gait to diminish.
• At full speed the foot’s directionality of movement has 0 deviation which decreases lower body movement and improves efficiency.

Landing Point Relative to Center of Mass

• Overstriding increases lower-limb joint loads, increasing the risk of running injury development
• The point of contact between the ground and initial contact during running at the COM
• The length between the third of the foot during a stride
• With sprinting should ground almost directly under the COM

Influence of Gait Velocity

• Increase influences biomechanical factors Has greater affect with forward momentum and flexibility and eccentric muscle control and excursion ability

Ankle and foot

• All bones reduce excursions in all 3 planes showing need for stiffer joints
• Slower running has longer stride distance, sprint phase stance
• In sprint phase, a person continues maintaining weight on foot but may lower heel to supporting ground.
• With some runners, those barefoot prefer initial front of foot strike

Comparing Heel and Forefoot strike patterns

• This has become more important with BORN to RUN and more people choosing to transition from a constant rear to front stance strike
• Front strike patterns have compliance of the dorsal area allowing for compliance and good absorption in order to reduce peak vertical force

Influence of fatigue on running Biomechanics

• Some runners can’t always complete certain actions as well as it appears on set or during certain periods with the bodies bio mechanics.
• Therefore tests should be had the clinicians available to see what results due to the bodies circumstances

Lower Limb Biomechanical Assessment in the Clinical Setting

• Efficient routine to assess lower limb biomechanics
• Includes distal to proximal approach with basic testing of stability.

Clinical Guiding Principles for Biomechanical Efficency

• Distaly to proximally
• Assess static to dynamic position

Foot Assessment

Subjectiveness (how abnormal does the foot appear), itemizes position, and assesses MTP and position during examination.

Foot posture Index/Evaluation

• Can score at various stages of position
• Talar (head tilt), lateral movement, naviculus, arch height or abducted positions

First MTP/METATARSO JONT examination

• Rapid evaluation test with normal dorsiflexion has intact fascia will evert a good test is evaluate posterior of the foot
• This provides good data for a possible Valgus foot

ANKLE DORSIFLEXION

• Must be had with both flexed and straight positions to ensure optimal values for flexion and function for knee
• Test values should generally be around 40-45 degrees of flexion and range with the knee
• The knee flexion angle should follow the knee caps or top of the feet.

TIBIO FEMORAL exam

• Must follow angle of the hip flexor extension test

Leg strength test examination

• Can show with discrepancies especially by way of stress or potential for pain by way of the joints

Static posture

• Allows to have knowledge of body with basic foot function, knee or strength

Summary of static assessment

Easy method to calculate function by way of just a few tests to gain results for proper bio-functionalities assessment.

Functional Lower Limb Tests

• Begins with a simple easy evaluation and then moves to more complicated and difficult situations in order for accurate biomechanics with progressions evaluations
• The patient’s progression is then pushed from one location and position into a more variable and then to an evaluation for full examination

Single Leg Stance Evaluation/Tests for Control

• Trunk strength for hip control and knee joint
• Stability of foot function and overall balance is also assessed

Lower Limb Biomechanical Observations

• Shows excessive asymetrical pelvic/trunk movement,
• Shows ROM
• Shows weak strengths, NMC and decreased muscle strength. and lumbar/SI joint.

Hip exam

Hip can have weak ROM with several areas for assessment for limited movements: abduction/internal rotation.

Knee

Apparent with a need ROM assessment is shown a need to increase the pressure at certain positions.

Ankle strength

Can be tested too for ROM or with ankle instability test.

Foot pronation

The same is observed to have type or impaired windless and instability on plantar position

FOOTWEAR AND TOOL

• Needs examination with proper structure and fit with pattern
• Is for proper people that are pronnatious especially

Most IMPORTANT PROPERTY/Characteristics TO EVALUTE

• Should also be examined by heel counter, the mid-foot stability as well as being durable. Especially during upper and lower testing.

CONDITIONS to review

• Important to note and confirm the benefits of each area
• The exam is also to determine the bio risks during testing.

Lower Limb Bio-Mechanical Abnormalities

• Next is the need for strategies for mechanical improvements in biomechanics And increasing evidence to incorporate a orthotics and exercises with improvement.

FOOT WEAR NEEDS DURING BIOMECHANICS

Needs proper pattern (verbal or video cues) and understanding with new tools (VIMove) to measure proper force during movement.

Types of Orthotics

All range from various qualities of flexible, soft, fabricated shelf testing. all provide a simple method but there can only be a minor improvement that the customer may require if they want the cheaper option with a small improvement There is generally 3 levels during orthotics evaluation that the clinician may follow: 1). Evaluation with range of motion.

Is a method to follow and see the success, if the patient provides enough feedback can it provide success over the patient's position and abilities.

Most important positions

• Are comfortable while being properly functional to provide to proper support; therefore they will help reduce future injury