Flashcards in 04 Knee Special Tests: Rotary Instability Deck (31):
What are the four rotary instability tests?
What is a rotary instability?
micro-transverse plane rotational instability
Why is rotary instability a problem?
due to ACL injuries and subsequent DJD even after good surgeries
What are the primary stabilizers of the knee?
In addition to the 4 primary stabilizers, which is another one? What if it's damaged?
- if it's not present, it must be recreated
- if it's torn, must reconstruct or do a primary repair
If the primary stabilizers are lost, what must you rely on?
What is the secondary stabilizer of the knee?
(if this is injured as well, creates even more problems)
With a rotary instability, what must remain intact?
PCL in rotary instability
- serves as the axis of rotation
- tibial plateau rotates around the PCL when a primary stabilizer is torn
testing position for rotary instability
- same as ant/post drawer
- knee is either in ER or IR, depending on which structures you want to tighten
For rotary instability, how do you test lateral structures?
tibia in IR
For rotary instability, how do you test medial structures?
tibia in ER
direction of force for rotary instability test
- straight sagittal plane
- DO NOT APPLY ROTATION PRESSURE
Why should you apply pressure in the sagittal plane for rotary instability?
tibia shouldn't rotate unless it's injured
How are the rotary instability tests named?
- tibial plateau that subluxates
- in the direction of applied force
What does ALRI test?
- middle 1/3 of lateral capsule
What movement will occur with a positive ALRI test?
What is pathoneumonic for ACL injury?
- Sigund's fx or lateral capsular sign
- menisco-tibial portion fractures because of rotational movement
Why are ACL injuries associated with avulsion fx?
because the tibia subluxates forward and violent twisting tears the lateral 1/3 of the capsule
leads to instability
common MOI for ACL tears
pivot shift (knee planted with rotation)
most to least common rotary instabilities
What does PLRI test?
- posterior 1/3 of lateral capsule
- arcuate complex
What does PLRI look like?
Devastating injury when the _______ and _______ are both involved
- arcuate ligament
- posterior lateral complex
What does AMRI test?
middle 1/3 of medial capsule
What does AMRI look like?
What is happening with a positive AMRI test?
medial tibial plateau subluxates anteriorly
What does PMRI test?
- posterior 1/3 medial capsule
What is PMOL?
posterior medial oblique ligament
What does PMRI look like?