biomechanics exam 3: lower extremity

pelvic girdle

positions hip joint for effective limb movement and is a single nonjointed structure but it can rotate in all three planes of movement

pelvis

made of two innominate bones that facilitates movement of the femur by rotating so that the acetabulum is positioned toward the direction of impending femoral movement

femur

major weight-bearing bone and is the longest, largest, and strongest bone in the body; weakest part is the femoral neck

what are the main ligaments that reinforce the hip joi

iliofemoral ligament

which ligament of the hip joint is extremely strong and known as the y ligament and is also the primary stabilizer for the femoral head against anterior translational and external rotation

iliofemoral and pubofemoral

which two hip joint ligaments strengthen the joint anteriorly

ischiofemoral

which hip joint posteriorly reinforces the joint

acetabuofemoral joint

what is the name of the ball-and-socket hip joint

full extension and internally rotated

what is the close-packed position of the acetabulofemorla joint

flexion/extension, abd/adduction, lateral/medial rotation

what are the motions of the hip

anterior/posterior tilt

what are the motions of the pelvis in the sagittal plane

lateral tilt

what are the motions of the pelvis in the frontal plane

forward/backward rotation

what are the motions of the pelvis in the horizontal plane

extension

what type of hip movement is posterior pelvic tilt in closed chain motion

internal rotation

if the toe moves in to decrease the angle, what is the motion of the hip

external rotation

if the toe moves out to increase the angle, what is the motion of the hip

iliopsoas

what are the major hip flexors- iliacus and psoas major, often jointly referred to as what because of their common attachment to the femur

hip flexion

in open chain movement, what motion do the hip flexors generate

anterior pelvic tilt and trunk flexion

in closed chain movement, what motion do the hip flexors generate

semitendinosus, semimembranosus, and biceps femorus

what muscles make up the hamstrings

hip extension

what motion(s) is the gluteus maximus responsible for

hip extension and knee flexion

what motion(s) is the semitendinosus responsible for

hip extension and knee flexion

what motion(s) is the semimembranosus responsible for

hip extension and knee flexion

what motion(s) is the biceps femoris responsible for

hip extension

in open chain movement, what motion do the hip extensors generate

pelvic posterior tilt and trunk extension

in closed-chain movement, what motion do the hip extensors generate

hip abductors

stabilize the pelvis during support phase of walking/running and when an individual stands on one leg

lateral to hip joint

where do the hip abductors lie

gluteus medius

what muscle is the major hip abductor

hip abduction

in open chain mm, what motion do the hip abductors generate

contralateral pelvic lateral upward tilt and prevent contralateral pelvic drop during one-leg standing 

in closed chain mm, what motion do the hip abductors generate

hip adductors

muscles that cross the hip joint medially and are regularly active during the swing phase of the gait cycle to bring the foot beneath body’s COG for placement during support phase

hip adduction

what motion does the adductor magnus generate

hip adduction

what motion does the adductor longus generate

hip adduction

what motion does the adductor brevis generate

hip adduction, medial rotation, and knee flexion

what motion does the gracilis generate

hip adduction

in open chain movement, what motion does the hip adductors generate

contralateral pelvic lateral downward tilt (in supine position)

in closed chain movement, what motion does the hip adductors generate

contralateral pelvic backward rotation

in closed chain mm, what motion do the hip external rotators generate

contralateral pelvic forward rotation

in closed chain mm, what motion do the hip internal rotators generate

when the hip is flexed 90 degrees

at what position does horizontal hip abduction and adduction occur at

same agonists as hip abduction/adduction after the hip flexors are activated

what are the primary movers for horizontal hip abd/adduction

posterior muscles because they are stretched when the femur is in 90 degrees of flexion

which muscles are more effective in horizontal abd/add

knee

large synovial joint with three articulations within a joint capsule

tibiofemoral joint

joint consisting of two condyles that form side by side condyloid joints that function as a modified hinge joint due to the restricting ligaments, with some lateral and rotational motions

patellofemoral joint

increases the angle of pull of quadriceps tendon on tibia, therefore improving the mechanical advantage of the quads for producing knee flexion

lateral motion

what motions do the lateral and medial collateral ligaments prevent

stretch the medial and potentially tear it

if a force at the knee was coming from the lateral side, what would happen

tibial attachments

what do the anterior and posterior names of ACL and PCL refer to

ACL

what ligament prevents posterior displacement of the femur on the tibia

ACL

what ligament prevents anterior displacement of the tibia on the femur

ACL

which knee ligament tightens during extension

PCL

what ligament prevents anterior displacement of the femur on the tibia

PCL

which ligament prevents posterior displacement of the tibia on the femur

PCL

which knee ligament tightens during flexion

biaxial joint

how many axes of rotation does the tibiofemoral joint allow

sagittal (flex/ext) and rotation (transverse)

which planes of motion does the tibiofemoral joint allow

full extension

what is the close packed position of the tibiofemoral joint

screw-home mechanism

describes how the medial condyle of the knee is longer than the lateral one so there must be a locking motion of the knee by slightly rotating it

tibia laterally rotates on the femur during the last 20 degrees of knee extension

during open chain movement, how does the knee “screw-home”

femur medially rotates on the tibia during the last 20 degrees of knee extension

during closed chain movement, how does the knee “screw-home”

popliteus

allows medial rotation of the tibia with respect to the femur during open chain mm to enable knee flexion to occur; acts as the locksmith

rotates the femur externally

how does the popliteus act during closed-chain mm

hamstrings (semitendinosus, semimembranosus, and biceps femoris

what muscles are the primary knee flexors

four quadriceps muscles

what muscles are the knee extensors

patellar tendon that attaches on the tibia

where do the four quad muscles distally attach to

patella

increases the moment arm for quads for force to be more efficient

inferiorly

in which direction does the patella glide during knee flexion

Q angle

quadriceps and patellofemoral angle that has the normal range of 13-19 degrees and is greater in females

medial tibia plateau

which condyle in the knee has a larger load put on it but also has a greater surface area to decrease the pressure

180-120 degrees of flexion

when is the forces at the knee the largest

30 degrees of flexion

when is the forces at the knee is the smallest

tension in the quads and patellar tendon

what are the two forces at the patellofemoral joint that creates compression in the knee

knee flexion during weight bearing

what does compression at the knee increase with

tibiotalar joint

what joint in the ankle allows for the most motion and is a hinge joint

inferior tibiofibular joint

which joint in the ankle is a syndesmosis

deltoid ligament is extremely strong on the inside

why does the ankle rarely roll inwards and stretches the lateral side

talocrural joint

what is considered the ankle joint

tibiotalar and fibulotalar

what joints make up the talocrural joint

hinge joint

what type of joint is the talocrural joint considered as to allow dorsiflexion and plantar flexion

inversion, plantar flexion, and adduction

what motions involve supination of the ankle

eversion, dorsiflexion, and abduction

what motions involve pronation of the ankle

gastrocnemius and soleus (calf muscles)

what are the primary plantar flexor muscles

tibialis posterior

what is the assistant plantar flexor muscle