Biomechanics Exam 2

what joint is the knee composed of?

tibiofemoral joint

what kind of joint is the knee?

double condyloid joint (modified hinge)

what are the bony structures of the knee?

femur, tibia, patella, and proximal fibula

what is normal angulation of the femur?

180 degrees

what is genu valgum

<170 (distal end angled AWAY from the midline)

what is another name for genu valgum?

knock-kneed

what is genu varum

>170 degrees (distal end angled TOWARDS midline)

what is another name for genu varum

bow-legged

what is the intercondylar eminence of the tibia and fibula?

separates condyles

what kind of cartilage covers the patella? What kind of loads is the patellar subjected to?

hyaline, high loads

where is the apex of the patella?

inferior border

where is the base of the patella

superior border

does the patella increase of decrease the moment arm of the knee extensors?

increase

what is the most effective range of degrees of knee flexion?

60-30 degrees

movement at the tibiofemoral joint produces _________ movements at the patellofemoral joint

simultaneous

what are the muscular attachments for both menisci? for just the lateral meniscus?

semimembranosus and quads, popliteus

what are the ligamentous attachments for the menisci?

MCL to medial meniscus

what kind of receptors do the menisci have?

mechanoreceptors and nociceptors

what is the purpose of bursae?

reduce friction between structures

the medial capsule of the knee is reinforced by:

medial retinaculum, tendons of sartorius, gracilis, semitendinosus, and MCL

Menisci follow the motion of…

the femoral condyles

Which meniscus is more mobile?

lateral meniscus

during knee flexion, as the tibia moves posterior, how does the meniscus move?

posteriorly

during knee extension, as the tibia moves anterior, how does the meniscus move?

anteriorly

what kind of force does the MCL resist?

valgus force

what kind of force does the LCL resist?

varus force

in which direction does the ACL run?

posterior to lateral femoral condyle (APL)

in which direction does the PCL run?

anterior to medial femoral condyle (PAM)

what forces need to occur to have an ACL tear?

planted foot, genu valgus, knee lateral rotation, hip adduction, and hip medial rotation

what are osteokinematics in the sagittal plane of the tibiofemoral joint?

flexion and extension

what are osteokinematics in the transverse plane of the tibiofemoral joint?

medial and lateral rotation

what are osteokinematics in the frontal plane of the tibiofemoral joint?

abduction and adduction

what is normal ROM of the tibiofemoral joint in the sagittal plane?

5-0-130

what is genu recurvatum?

hyperextension beyond 10 degrees from 0 position

what are the causes of genu recurvatum?

weak quads and tight gastroc

what is normal knee ROM required for walking on a level surface

65

what is normal knee ROM required for ascending stairs

80-105

what is normal knee ROM required for descending stairs

85-110

what is normal knee ROM required for moving from sitting to standing

90-95

what is normal knee ROM required for moving from standing to sitting

95

what is normal knee ROM required for donning socks

120

what is normal knee ROM required for squatting with heels up

160

patellofemoral osteokinematics - patella slides in intercondylar groove during flexion and extension in the _____ direction as the tibia

same

when does maximal contact occur with the intercondylar groove and the patella?

between 60-90 degrees of flexion

what is PFPS?

patellofemoral pain syndrome

what condition if common with PFPS?

lateral patellar tracking

what is a q-angle

measurement of the line of pull of the quadriceps

how is the q-angle formed

line between the ASIS to the midpoint of the patella AND the line along the long axis of the patellar tendon

what is a normal q-angle

13-15 degrees

greater lateral muscle pull of the patella = …

q-angle > 15 degrees

larger q-angle = _____ injury risk

larger

are men or women more likely to be affected by knee injuries?

women

during open chain motion, when the tibia is moving on the femur during extension (concave on convex) the tibia rolls _____ and slides ______

anteriorly, anteriorly

during closed chain motion, when the femur is moving on the tibia during extension (convex on concave) the femur rolls _____ and slides ______

anteriorly, posteriorly

during open chain motion, when the tibia is moving on the femur during flexion (concave on convex) the tibia rolls _____ and slides ______

posteriorly, posteriorly

during closed chain motion, when the femur is moving on the tibia during flexion (convex on concave) the femur rolls _____ and slides ______

posteriorly, anteriorly

what is the screw-home mechanism?

tibia laterally rotates to lock the knee in extension

during what degree of knee extension does the screw-home mechanism occur?

last 20-30 degrees

which muscle unlocks the knee?

popliteus

closed chain knee flexion causes what kind of rotation?

lateral femoral rotation

open chain knee flexion causes what kind of rotation?

medial tibial rotation

what is axial rotation at the knee?

arthrokinematic spin occurs between the menisci and the femoral and tibial articular surfaces

what are the knee extensors?

rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

are the quads contracting concentrically or eccentrically to lower the body from standing to sitting?

eccentrically

when are the quads most effective?

80-30 degrees flexion

at what degree does the vastus lateralis pull?

35 degrees

at what degree does the VML pull?

15-18 degrees

at what degree does the VMO pull?

55 degrees

what are the knee flexors and rotators?

semimembranosus, semitendinosus, and biceps femoris

what muscles flex and rotate the knee and attach to the pes anserine?

gracilis, sartorius, and semitendinosus

how many joints does the gastroc cross?

two

what two things does hip position dictate?

range of motion available at the knee

whether muscles that cross the knee are actively or passively insufficient

hip flexion with knee extension can be limited by two things… what are they and how are they limiting?

tight hamstring - passive insufficiency, weak rec fem - active insufficiency

hip extension with knee flexion can be limited by two things… what are they and how are they limiting?

tight rec fem - passive insufficiency, weak hamstring - active insufficiency

when does knee flexion occur with hip flexion?

when walking and running

when does knee extension occur with hip extension?

when standing from sitting, stairs, running

when going to standing from sitting, what is acting on the knee? On the hip? are they concentric or eccentric motions?

quads concentrically extend the knee, hamstrings concentrically extend the hip

when going to sitting from standing , what is acting on the knee? On the hip? are they concentric or eccentric motions?

quads eccentrically control knee flexion, hamstring eccentrically control hip flexion

what is tibial torsion?

distal end of tibia rotates 20-35 degrees laterally compared to the proximal end

How much weight does the lateral malleolus carry?

7-10%

what ligaments are on the lateral side of the foot/ankle?

ATFL, CFL, PTFL

What ligaments are on the medial side of the foot/ankle?

deltoid ligament

What ligaments make up the deltoid ligament?

anterior tibiotalar, posterior tibiotalar, tibionavicular, tibiocalcaneal

what ligament is hurt in a high ankle sprain?

syndesmosis ligament

how much force do the talus and tibia bear (compressive forces)

90-95%

in the talocrural joint, what is the convex surface and what is the concave surface

talus - convex, tibia + fibula - concave

during open chain dorsiflexion, the talus rolls ______ and slides ______

anteriorly, posteriorly

during open chain plantarflexion, the talus rolls ______ and slides ______

posteriorly, anteriorly

motion occur around which axis for the subtalar joint? what motion occurs in this joint?

oblique axis, inversion/eversion

when in weight bearing in the subtalar joint, which bone is moving on which?

talus moves on calcaneus

when in non-weight bearing in the subtalar joint, which bone is moving on which?

calcaneus moves on talus

during open chain inversion, in which direction does the calcaneus roll and slide?

rolls medially, slides laterally

during open chain eversion, in which direction does the calcaneus roll and slide?

rolls laterally, slides medially

what makes up the midtarsal (transverse tarsal) joint?

talonavicular joint (medial)

calcaneocuboid joint (lateral)

what are the stabilizing ligaments for the midtarsal joint?

spring ligament (calcaneonavicular), calcaneocuboid ligament, long and short plantar ligaments

what is foot/ankle pronation?

eversion, abduction, and dorsiflexion

what is foot/ankle supination?

inversion, adduction, and plantarflexion

what is normal inversion at the transverse tarsal joint?

20-25

what is normal eversion at the transverse tarsal joint?

10-15

what kind of joints are intermetatarsal joints?

synovial joints