KIN 307 quiz 5

What is considered the largest joint in the body?

What is considered the largest joint in the body?

the knee joint

What type of joint is the knee joint and what actions is it capable of?

hinge; flexion, extension, internal rotation, external rotation

What articulates to form the knee joint?

Enlarged condyles of the femur articulate on enlarged condyles of the tibia

What are the articulations within the area of the knee joint?

Medial tibiofemoral, Lateral tibiofemoral, Patellofemoral

What is the patellofemoral joint?

patella is covered with thick hyaline cartilage on the posterior surface and slides in the trochlear groove of the femur; it functions in improving the angle of pull and centralizes forces

What bone bears all the weight of the femur?

tibia

What is the patella and what is its function?

sesamoid bone imbedded in quadriceps and patella tendon; Serves as a pulley to improve the angle of pull, resulting in a greater mechanical advantage during knee extension

What is the fibula?

serves as the attachment for knee joint structures.

-Does not articulate with femur or patella

-Not considered part of knee joint.

What produces dynamic stability of the knee joint?

Contractions of quadriceps and hamstrings

What produces static stability of the knee joint?

ligaments

what are the menisci of the knee and what are their functions?

• form cushions between bones.

• fibrocartilage disks attached to tibia.

• Deepen tibial fossa to enhance stability (deepens joint contact by 70%)

• Thicker on outside border and taper down very thin to inside border.

• Absorbs Shock (also lessens friction in joint by 20%).

• Site of secondary muscle attachment.

What are the ligaments of the knee?

Role is to hold the femur in contact with the tibial plateau.

• Anterior Cruciate Ligament (ACL)

• Posterior Cruciate Ligament (PCL)

• Medial Collateral Ligament (MCL)

• Lateral Collateral Ligament (LCL)

What is the MCL?

Medial Collateral Ligament (MCL) maintains medial stability by resisting valgus forces or preventing knee from being abducted

What is the LCL?

Lateral Collateral Ligament (LCL) maintains lateral stability by resisting varus forces or preventing knee from being adducted

What is the ACL and PCl named for?

tibial attachment

What type of stability does the ACL and PCL provide?

anterior/posterior stability, as well as rotatory stability

The ACL prevents the femur from sliding _____ on the tibia or the tibia from sliding ________ on the femur

posteriorly; anteriorly

The PCL prevents the femur from sliding _____ on the tibia or the tibia from sliding _________ on the femur

anteriorly, posteriorly

Other stability of the knee joint:

• Tendons of Pes Anserinus: Sartorius, Gracilis, & Semitendinosus

• Medial/Lateral retinaculum

• Iliotibial band: thick, strong band of tissue connecting tensor fascia latae to femur and tibia

The screw home mechanism:

Automatic external rotation of tibia as the knee moves from 15° of knee flexion to full extension, this happens because of osteokinematics

What is the automatic external rotation caused by?

• Larger medial femoral condyle.

• Longer anterior-posterior dimension of tibial medial condyle – through passive tension in ACL.

• Lateral pull of Quadriceps

• Knee is unlocked by the internal rotation function of the popliteus.

Quadriceps “Q” angle

angle formed by intersection of lines connecting:

• ASIS & mid-patella

• Tibial tuberosity & mid-patella

true or false: the “q” angle is larger in females than it is in males

true

Can higher “q” angles cause problems?

yes; lateral patellar subluxation or dislocation, patellar compression syndrome, chondromalacia, and ligamentous injuries

How can high “q” angles be maintained?

high levels of strength and endurance in vastus medialis so as to counteract lateral pull of vastus lateralis

genu varum

a Q-angle less than normal often leads to a “bowlegged” appearance

genu valgum

a Q-angle greater than normal often leads to a “knock-kneed” appearance

What type of muscles in the knee mostly made up of?

biarticulate muscles (hamstrings and rectus femoris)

What movements can the knee complete?

flexion/extension; internal/external rotation

What muscles extend the knee?

Rectus femoris, Vastus medialis, Vastus intermedius, Vastus lateralis

What muscles flex the knee?

Biceps femoris, Semimembranosus, Semitendinosus

What muscles assist in knee flexion?

Sartorius, Gracilis, Popliteus, Gastrocnemius

Two-joint muscles are most effective when either the origin or insertion is _______ to prevent movement in direction of the contracting muscle

stabilized

To a degree, muscles are able to exert greater force when ______ than when ________

lengthened; shortened

pes anserinus is formed by:

Gracilis, sartorius, and semitendinosus joined together distally

How do the Gracilis, sartorius, and semitendinosus provide dynamic stability in any knee rotation movement?

Their attachment to proximal tibia combined with posteromedial line of pull enables them (particularly external rotation once the knee is flexed and hip is externally rotated)

The _______ increases its total length and becomes a better flexor at knee when pelvis is rotated posteriorly and stabilized by abdominal muscles

sartorius (think about leaning back in a chair and crossing your leg vs leaning forward)

_______ inserts on lateral side of knee while _________ insert on medial side of knee

Biceps Femoris; semitendinosus & semimembranosus

What muscles externally rotate the knee?

biceps femoris

What muscles internally rotate the knee?

semitendinosus, semimembranosus, popliteus

true or false: knee flexors are stronger than knee extensors

false