BME 4370 Exam 2

What are the joints of the knee?

Tibiofemoral and Patellofemoral

How many degrees of freedom are there in the knee?

6

What is adduction?

Movement towards the midline.

What is abduction?

Movement away from the midline.

What is varus?

Angled outward

What is valgus?

Angled inward

What are the ligaments in the knee?

ACL, PCL, LCL, MCL, lateral meniscus, medial meniscus

What movement does the MCL restrict? How could this ligament be injured?

Sideways movement, excessive side or twisting motion

Does the knee become tighter or looser with increased flexion angle?

Looser

What is rotation of the knee limited by?

Ligaments, capsule, menisci

What is osteokinematics?

Gross observable movement of bones in space (joint angles)

What is arthrokinematics?

Joint surface motion; roll, slide, rotation of tibia relative to femur

What is the knee instant center of rotation?

The point in space around which the tibia appears to rotate relative to the femur at any instant

What are the components of actual knee motion?

Sliding and rolling

What is the four bar linkage model?

Explains how the knee both slides and rolls, only in the sagittal plane, ACL and PCL are cross links

What is the screw home mechanism?

Rotation that tightens the ACL, collateral ligaments, joint capsule; increases bone congruence.

What is the benefit of the screw home mechanism?

Stability and reduce force on joints

What unlocks the screw home mechanism?

Popliteus muscle

What is the knee axis of rotation?

Imaginary line about which the tibia is rotating about the femur at any given instant, not fixed

Is the knee a true hinge joint?

No

Where do the medial and lateral collateral ligaments attach to the femur?

Near the knee axis of rotation

Why do the collateral ligaments attach at the knee axis of rotation?

To maintain constant length and tension during movement

What do the anatomic landmarks (axes) tell us about tibiofemoral motion during different activities?

Shows that they change depending on activity W

What causes different knee motions?

Joint geometry, ligament constraints, and muscle loads

What is the patellofemoral joint?

The joint where the patella slides relative to femur

What is the contact of the patella until 90 degrees?

Continuous across medial and lateral sides of trochlear groove

What is the contact of the patella after 90 degrees?

Splits into separate locations on medial and lateral side

In what direction does the contact of the patella move with increasing flexion angle?

Superior direction

What does the e-tibia instrumented knee measure?

Tibiofemoral contact forces

Why are knee forces greater in crouch gait?

The bent knee requires muscles to work harder to support the weight of the body

What is the hip joint called?

Acetabulum

What is the labrum?

Fibrocartilaginous ring attached to the rim of the acetabulum that deepens the socket and improved joint stability

What is the transverse acetabular ligament?

Spans the acetabular notch and completes the socket

What is the ligamentum teres?

Connects the femoral heal to acetabulum and contributes to stability at extreme ranges of motion; contains proprioceptors and nociceceptors

What is fibrocartilaginous?

Different from articular cartilage

Is the labrum loaded in tension or compression?

Tension

What is the function of the labrum?

Creates fluid seal at the hip

What is the acetabulum cavity?

Faces obliquely forward, outward, and downward

What are the consequences of a misaligned acetabulum?

Does not adequately cover the femoral head; chronic dislocation and osteoarthritis

What is the center edge angle and what are the consquences of a small angle?

Coverage of the acetabulum in the frontal plane; less geometric constraint and risk of dislocation

What is acetabular dysplasia?

Abnormal center edge angle and shallow acetabulum that causes hip instability and degenerative arthritis in mid-late adulthood

What is the acetabular anteversion angle?

Transverse plane coverage with an average of 20 degrees

What is coxa valga?

Moment arm is shortened by 25% (T=F*0.75d)

What is coxa breva?

Moment arm shortened by 20% (T=F*0.8d)

What happens when muscle force does not change in the hip?

The ability to generate torque is reduced. h

What is Trendelenburg gait?

An upper body shift with pelvic drop

What is a normal torsion angle in the hip?

10-20 degrees

What is femoral anteversion?

Femoral neck rotated anteriorly relative to distal femur (> 12 degrees); pigeon-toed gait

What is femoral retroversion?

Femoral neck rotated posteriorly relative to distal femur (< 12 degrees); external rotation of leg W

What is the femoral head composed of?

Interior is cancellous bone and exterior is cortical bone that progressively thickens

What are the effects of aging on the femoral head?

Loss of bone density

What are the consequences of hip fracture in older adults?

Loss of mobility and independence, increased risk of medical complications, reduced quality of life, and higher mortality risk W

What is the purpose of hip muscle line of action?

Determine specific directional torque and mechanical leverage the muscle exerts on the femur and pelvis

What are the regions of the foot and ankle?

Rearfoot, midfoot, forefoot

What is the model for the foot arch?

Beam model of longitudinal arch; tension on inferior, compression on superior

What causes microdamage on the plantar fascia?

Excessive loading on the calcaneus, which causes heel pain

How is body weight accepted and dissipated in the foot?

Elongation of the plantar fascia

What happens to the fascia during toe extension?

The fascia tightens, elevating the arch, and creating a rigid lever for push off

What are the 4 ankle motions?

Dorsiflexion, plantarflexion, inversion, eversion

What is pronation?

Eversion, dorsiflexion, abduction; flexible shock absorber

What is supination?

Inversion, plantarflexion, adduction; rigid lever for push off

What are the joints that make up the ankle joint complex?

Tibiotalar, fibulotalar, tibiofibular, talocrural

Which ankle joints have little motion?

Fibulotalar, tibiofibular

What makes up the talocrural joint?

Tibia, fibula, talus

What type of joint is the is the talocrural joint?

Mortise joint

What does the talocrural joint account for?

Almost all sagittal plane motion at the ankle

The talocrural joint axis is determined by the geometry of the:

Talar trochlea, distal tibia, distal fibula

What is ankle syndesmosis?

Fibrous joint that connects the distal tibia and fibula

What are the functions of the ankle syndesmosis?

Maintains ankle mortis, allows slight widening of mortise during dorsiflexion, transmits forces, important motion for ankle mechanics

What makes up the subtalar joint?

Talus and calcaneus bone

What is the subtalar joint responsible for?

Inversion, eversion

How many degrees of freedom does the subtalar joint have?

1

What is the function of the subtalar joint?

Works with talocrural to provide motion in all three planes and allows the foot to adapt to uneven surfaces

What are the articulations of the transverse tarsal joint?

Talonavicular joint, calcaneocuboid joint

What is the function of the transverse tarsal joint?

Increase mobility, all adaption, create rigid lever

What locks and unlocks the transverse tarsal joint?

Subtalar joint supination locks, pronation unlocks

What does the tarsometatarsal joint allow?

Allows the forefoot and midfoot to function as a single rigid unit

What are the consequences of lisfranc injury?

Impaired push off strength, reduced propulsion efficiency, arch collapse, chronic midfoot pain

What position makes the foot more stable?

Supination

What makes the foot more flexible?

Pronation

What is the order of injury frequency of ligaments during ankle sprains?

Anterior talofibular, calcaneofibular, posterior talofibular

When is the anterior talofibular ligament stressed?

When ankle is plantarflexed and inverted

The muscles in the foot and ankle cause what type of motion?

Dorsiflexion

The lateral malleolus acts as a what to change the line of action in the ankle?

A pulley

What is the action of the gatrocs and soleus?

Plantarflexion

What is the motion segment of the spine?

Smallest biomechanical unit of the spine the exhibits the mechanical behaviors of the whole spinal column

What are the components of the motion segment of the spine?

Two adjacent vertebrae, intervertebral disc, facet joints, ligaments connected vertebrae

What is the intervertebral disc made of?

Nucleus pulposus and annulus fibrosus

What is the nucleus pulposus?

Primary load-distributing structure that is mostly water and behaves like a hydrostatic fluid under pressure; pressure is transferred to annulus fibrosus

What is the annulus fibrosus?

Consists of concentric layers with tensile hoop stresses that alternate orientation of the collagen fibers; oriented at an angle of 30 degrees to the vertebral body and 120 degrees to each other

What happens to the intervertebral disc under compressive loading?

Stress is not uniformly distributed; NP has compression, AF has hoop tensile, compressive, tensile stresses

What contributes to fissures, bulging, and herniation of discs?

Disc degeneration reduces nucleus pressurization and load shifts to annulus and facet joints

What is the function of cervical facet joints?

Mobility, large movements, greatest overall mobility of spine

Why would you need a lot of mobility in the cervical spine?

Position of head, eyes, ears for daily activities

What are the functions of the thoracic facet joint?

Rotation and rib cage stability, axial rotation, restricts flexion-extension, trunk stability

Why would you want trunk stability in the thoracic region?

Protect vital organs, support posture, prevent injury

What are the functions of the lumbar facet joint?

Load bearing and stability, greatest overall mobility in spine, allows flextion-extension, restricts axial rotation, stability during lifting/weight bearing

What are the consequences of excessive rotation in the lumbar region?

Creates high stresses on disc and facet joints, sagittal orientated facets help prevent this

How is the line of gravity for the trunk orientated?

Anterior to the transverse axis of motion of the spine

What type of movement is the spine subjected to constantly?

Forward bending; creates a flexion moment and spine must create extension moment