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
6
New cards
What bone bears all the weight of the femur?
tibia
7
New cards
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
8
New cards
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.
9
New cards
What produces dynamic stability of the knee joint?
Contractions of quadriceps and hamstrings
10
New cards
What produces static stability of the knee joint?
ligaments
11
New cards
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.
12
New cards
What are the ligaments of the knee?
Role is to hold the femur in contact with the tibial plateau.
Medial Collateral Ligament (MCL) maintains medial stability by resisting valgus forces or preventing knee from being abducted
14
New cards
What is the LCL?
Lateral Collateral Ligament (LCL) maintains lateral stability by resisting varus forces or preventing knee from being adducted
15
New cards
What is the ACL and PCl named for?
tibial attachment
16
New cards
What type of stability does the ACL and PCL provide?
anterior/posterior stability, as well as rotatory stability
17
New cards
The ACL prevents the femur from sliding _____ on the tibia or the tibia from sliding ________ on the femur
posteriorly; anteriorly
18
New cards
The PCL prevents the femur from sliding _____ on the tibia or the tibia from sliding _________ on the femur
anteriorly, posteriorly
19
New cards
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
20
New cards
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
21
New cards
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.
Two-joint muscles are most effective when either the origin or insertion is _______ to prevent movement in direction of the contracting muscle
stabilized
34
New cards
To a degree, muscles are able to exert greater force when ______ than when ________
lengthened; shortened
35
New cards
pes anserinus is formed by:
Gracilis, sartorius, and semitendinosus joined together distally
36
New cards
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)
37
New cards
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)
38
New cards
_______ inserts on lateral side of knee while _________ insert on medial side of knee
Biceps Femoris; semitendinosus & semimembranosus
39
New cards
What muscles externally rotate the knee?
biceps femoris
40
New cards
What muscles internally rotate the knee?
semitendinosus, semimembranosus, popliteus
41
New cards
true or false: knee flexors are stronger than knee extensors