Lecture #7 (Knee, Hip & Pelvis) Flashcards
True or false:
The knee joint is made up of three articulations.
True: between the medial and lateral condyles and tibial plateau and between the patella and femur
What is the correct classification of the knee joint?
Double condyloid
What is the open packed position of the knee joint? Closed packed?
Open= 25 degrees flexion Closed= full extension
How far can the tibia rotate? Is this in weight bearing or NWB?
NWB about 50 degrees
How does tibial rotation occur during weight bearing?
The femur rotates medially on the tibia…this is that screw home mechanism
What are the circular rims of fibrocartilage found in the knee that are good for compression stresses, not shear forces?
Mensci (the lateral is an incomplete circle and the medial is a “C” shape)
What are the functions of the mensci (x5)?
Protection, stability, lubrication, force transmission, and aiding in roll of femoral condyles
Which meniscus is more often injured, why?
Medial because is moves less than the lateral meniscus but mainly because it takes most of the sliding and gliding of the joint (medial condyle is bigger)
How much does the medial meniscus move? The lateral? In what direction do they move?
Medial= 6mm
Lateral= 12mm
They move in an A/P direction
What is the unholy triad?
The ACL, MCL, and medial meniscus,,,there is also some attachment of the medial meniscus to the semimembranosis
What is the lateral meniscus attached to?
The PCL and coronary ligaments (not to the LCL)
Where does a meniscal cyst occur?
Lateral meniscus
Where is the vascularization of the menisci located?
In the outer 1/3…this is why the menisci do not really heal well because they have very little blood supply
Where does a meniscus tend to be stiffer and where does it tend to be weaker?
Stiffer= circumferentially Weaker= radially
What does the MCL and LCL do?
Prevent rotation of the tibia on the femur when the knee is extended (they are taunt then) and protect from varus and valgus forces
What structure helps support the medial knee in addition to the MCL? What about the lateral knee in addition to the LCL?
Medial knee= MCL and pes anserine
Lateral knee= LCL and IT band
What ligament prevents posterior displacement of the tibia on the femur? What else does this ligament do?
PCL–it also helps prevent hyperextension of the knee
What ligament prevents anterior translation of the tibia and serves as a secondary support to varus and valgus forces on the knee? What else does it prevent?
ACL–it also helps prevent excessive rotation of the tibia on a fixed femur
How many bands of the ACL are there? What are they?
3–anteromedial
intermediate
posterolateral
During what motion do the cruciate ligaments become taunt and rub against one another? During what motion do they become lax?
Taunt= medial tibial rotation & femoral lateral rotation Lax= lateral tibial rotation & femoral medial rotation
Where does the peak stress on the ACL occur? Why?
Between 28 and 14 degrees of extension…because the angle of pull from the quads changes
How much stress is placed on the ACL during OKC exercises?
60% (but it increases more as you extend the knee)
What is the normal amount of valgus that people tend to have?
5-10 degrees
What measurements constitute genu varus and genu valgum?
Genu varum= 180 degrees and over (bowlegged)
Genu valgum= 165 degrees or less (knock-kneed)
A varus knee compresses which compartment of the knee? A valgus knee?
Varus= medial compartment Valgus= lateral compartment
What the Q-angle for men? Women? Genu varum? Genu valgum?
Men= 10-15 degrees
Women= 15-20 degrees
Genu varum= less than 10 degrees
Genu valgum= more than 15 or 20 degrees
What is the screw home mechanism?
Medial rotation of the femur (or external rotation of the tibia) during close chain movement. This is what allows us to stand up (full extension of knee) without activating any muscles
What does the PCL and menisci do during the screw home mechanism?
Stop the anterior rolling of the femur & help start a posterior glide of femur
What creates the “locked” knee at the end of the screw home mechanism?
Rotation at the knee and the extension at the hip
What unlocks the knee during closed chain?
Action of the popliteus and hip flexion