Knee Flashcards
What kind of joint is the knee?
Condyloid joint - 2 degrees of freedom (flexion/extension; IR/ER when flexed)
Stability of the knee comes primarily from
Soft tissues, ligaments, and muscles, not bones
Normal genu valgum
170-175 degree angle on the lateral side of the knee; formed by the femur which is angled medially (due to the 125 degree inclination) and the tibia which runs straight up and down.
Should be developed by 3 years of age
Excessive genu valgum
Less than 165 degrees
Genu varum
Greater than 180 degrees.
As one ages and developed arthritis, it’s more common for people to develop genu varum because the medial compartment shuts down and you begin to have compression medially and tension laterally
Why would someone have a poor squat position? (knock kneed position)
(Knock kneed position is femoral adduction and IR)
Weak gluteus medius, and poor eccentric control of the posterior lateral hip muscles, they can’t eccentrically control the femur from collapsing. Requires major proximal strengthening neuromuscular control program for the hips
Capsule encloses … and is reinforced by …
Medial and lateral tibiofemoral joints and PFJ.
Capsule is reinforced by fascia, ligaments, and muscles
Patella
Top called the base or superior pole. Bottom called the apex or inferior pole.
Posterior side has 3 facets: lateral, medial, and odd facet (most medial).
Sesamoid bone - increases mechanical advantage (increases IMA). If you don’t have a patella you can’t produce as much quad torque
Tibiofemoral joint
Between the convex femoral condyles and the flat (concave) tibial plateaus.
Shape of this joint permits extensive motion in the sagittal plane (0-140 degrees of flexion).
Stability from muscles, ligaments, and fascia
Menisci are what type of discs
Fibrocartilaginous discs - handles compressive forces much better than hyaline cartilage does
The menisci are anchored to the
intercondylar region of the tibia plateau by their anterior and posterior horns
External edges of the menisci are attached to the tibia and capsule by
Coronary (meniscotibial) ligaments
Coronary ligaments are
Relatively loose, allowing the menisci to pivot, especially lateral
What connects the two menisci anteriorly?
Transverse ligament
What attaches to the medial meniscus? The lateral meniscus?
Semimembranosis attaches to the medial, and the popliteus attaches to the lateral.
They stabilize the menisci during movement
Blood supply to the meniscus is
Greatest near the periphery, otherwise it’s 75% avascular, can’t really heal themselves
Where does the pain come from when the menisci are torn?
It comes from the inflammatory process, not the tear itself. Menisci are predominately aneural, except near the anterior and posterior horns, so there are no pain fibers to the meniscus. People with arthritis can have tears and not know because they have such small degenerative tears that they never elicited an inflammatory process and aren’t capable of producing pain by themselves
Medial meniscus
C-shaped, external border attaches to MCL
Lateral meniscus
Circular shaped, external border attaches only to lateral capsule. Also attaches to the femur via posterior meniscofemoral ligaments
Popliteus tendon passes between
LCL and lateral meniscus
What happens when surgeon does a meniscectomy?
Removes piece of meniscus, changes the weight bearing forces to the articular cartilage. Individual is likely to develop early arthritis, so whenever possible the surgeon wants to save as much of the meniscus as they can
Primary function of the menisci
To reduce compressive stress at the TFJ
Secondary functions of the menisci
Stabilize the joint during movement Lubricating articular cartilage Reducing friction Guiding the knee's arthrokinematics Increase bony fit of TFJ