Biomechanics WK 3- DPT

The picture below represents a patient attempting to perform a straight leg raise.  This patient has some quadriceps weakness and is unable to maintain the knee in an extended position while performing the straight leg raise.  Fully extending the knee through terminal knee extension places large demands on the quadriceps.  This inability to maintain the knee in full extension during a straight leg raise is known as:

extensor or quadriceps lag

There are several 2 joint muscles that cross both the hip and the knee joint.  Which of the following is NOT a two joint muscle that can move both the hip and the knee:

biceps femoris short head

This 2 joint muscle can flex the hip AND flex the knee:

sartorius

what are medial rotators of the knee:

semimembranosus, sartorius, popliteus

what are the 3 muscles of pes anserine

sartorius, gracilis, semitendinosus

what are functions of the menisci of the knee:

• dissipate pressure of the femoral condyles on the tibial plateau

• deepen the concavity of the tibial plateaus

• improve the congruity between the femoral condyles and the tibial plateau

This part of the meniscus is considered to have the most abundant blood supply and because of that is sometimes referred to as the red-red zone.  Tears in this area of the meniscus are often surgically repaired because of the potential for these tears to heal:

outer third

A valgus force at the knee (a force applied to the lateral aspect of the knee and directed medially, abducting the tibia on the femur as pictured below) will most stress which of the following ligaments:

medial or tibial collateral ligament

An anterior drawer test (attempting to pull the tibia anteriorly on the femur as pictured below) will most stress which of the following ligaments:

anterior cruciate ligament

The concave-convex rule dictates the pattern of rolling and gliding that occurs at a joint.  Which of the following statements best describes the arthrokinematics that occur with OPEN chain knee extension (tibia moving on femur):

tibia rolls and glides anteriorly on the femur

Which of the following statements best describes the arthrokinematics that occur with CLOSED chain knee extension (femur moving on tibia)

femur rolls anteriorly and glides posteriorly

At the end of CLOSED chain knee extension, some rotation occurs to put the knee in the screw home position.  Which bone rotates and in which direction to create the screw home position in CLOSED chain knee extension:

femur internally rotates

Unlocking the knee or moving it out of the screw home position is a necessary first step to allow knee flexion to occur.  Which muscle is primarily responsible for the rotation that occurs to unlock the knee and to allow knee flexion to take place:

popliteus

The quadriceps angle or Q angle is an angle that measures the lateral pull of the quadriceps muscle.  It is the angle between a line connecting the mid patella and the ASIS and a line connecting:

the mid patella to the tibial tuberosity

An increased Q angle does not correlate with patello-femoral pain.  However, an increased dynamic Q angle does correlate with patello-femoral pain.  During a single leg squat, what would you observe to indicate an increased dynamic Q angle:

the knee would move medially creating an increased angle of knee valgus

In which of the following muscles, would you expect the highest innervation ratio:

gluteus maximus

A muscle will produce the greatest force when it is held at what percentage of its resting length:

110% stretched slightly

Your patient is lying prone and fully extends his hip (1).  He then flexes his knee and tries again to extend his hip but cannot extend his hip as far (2).  This lack of hip extension occurs because the hamstrings cannot shorten enough to move the hip through full range with the knee flexed.  The hamstrings lack the functional excursion to move all the joints over which they pass through the full range of motion.  The hamstrings are experiencing:

active insufficiency

Your patient is lying supine and flexes her knee and hip bringing her knee to her chest (1).  She then extends her knee and again tries to flex her hip as far as possible but cannot flex her hip as far (2).  In this case, the hamstrings are experiencing:

passive insufficiency

What terms would you use to describe the fiber arrangement of the rectus femoris.
Would it be 1) parallel or oblique and 2) what type of fiber arrangement:

1) oblique, 2) bipennate

2 joint muscle- works at hip and knee

rectus femoris

all vasti only work at what joint

knee

deepest vastus

vastus intermedius

what muscle is an accessory extensor and keeps the capsule out of the way during flex/ext

articularis genu

what are the primary knee extensors

rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

what compartment are the knee extensors a part of

anterior compartment

which vastus tends to atrophy more quickly with disuse or immobilization

vastus medialis

which muscle becomes actively insufficient with hip flexion greater than 90° and knee extension

rectus femoris

secondary knee extensors

articularis genu and TFL

knee extension limited by:

• posterior capsule

• arcuate and oblique popliteal ligaments

• hamstring tightness

• tight collateral ligaments

what compartment are the knee extensors

posterior compartment

what muscles are the primary knee flexors

• semitendinosus, semimembranosus, biceps femoris (long head)

• biceps femoris (short head)

• popliteus

flexion limited by:

• soft tissue approximation

• cruciates

• anterior tibial collateral ligament

• quadriceps tightness

gluteus maximus is what part of the “delt of the hip”

posterior delt, extends and ER hip

gluteus medius is what part of the “delt of the hip”

middle delt, abduct hip

TFL is what part of the “delt of the hip”

anterior delt, flexion and IR hip

tibia has more rotation in which direction (medial or lateral)

lateral rotation

external rotation limited by:

• cruciates

• medial capsule including tibial collateral ligament

• pes anserine tightness

internal rotation limited by:

• cruciates

• lateral capsule

• biceps femoris tightness

degrees of flexion needed for normal walking

40-60°

what type of joint is the knee

diarthrosis

what type of diarthrosis is the knee

biaxial, condyloid

how many axes and degrees of freedom does the knee have

2

what axes does the knee pass through

flex/ext axis and rotation axis

tibio-femoral joint LPP

25° flexion

tibio-femoral joint CPP

full extension and lateral rotation of the tibia (screw-home)

degrees of flexion in the knee

0-135° full flexion

tibia moves on femur in which chain movement

open chain

femur moves on tibia in which chain movement

closed chain

external and internal rotation of the tibia is what movement

spin

purpose of patella

• improve mechanical advantage of quads

• dissipates compressive forces exerted by quads

patella glides what direction as the knee extends

superiorly

patella helps most at what degree of flexion

45°

what open chain movement is bad for patello-femoral pain

TKE and SAQ

what closed chain movement reduces pain and uses more quads

TKE

least to greatest patellar loading activities

walking, climbing stairs, descending stairs, squatting

squats are closed chain knee flexion that is ____ for patello-femoral pain

bad

open chain knee flexion lessens the load and should stay in what degrees

• 90° —> 45°

not TKE!!

Q angle normals for men and women

men: 8-14°

women: 11-20°

larger Q angle will pull patella which way

laterally

is static or dynamic Q angle predictive of patello-femoral problems

dynamic

exercises for patello-femoral pain syndrome

• TKE

• open chain 90°- 45°

• strengthen abduction and ER

what is innervation ratio

how many muscles fibers are in one motor unit

low innervation ratio examples

fine controlled contraction

• fingers, eyes

high innervation ratio examples

quads, back, glute max

factors influencing muscle force production

• motor unit recruitment

• fiber arrangement

• cross sectional area

• muscle length

• speed of muscle contraction

• leverage temperature

• fatigue

functional excursion

how far a muscle can go after being max elongated