Knee Injuries Flashcards
the anterior cruciate ligament attaches from the
anterior medial tibial plafond and to the medial aspect of the lateral femoral condyle
knee injuries commonly involve what
the medial meniscus, tibial collateral ligament/ anterior cruciate ligament (Lachman test, drawer sign, aspiration, arthroscopy)
what are popliteal cysts (Baker’s cysts)
are outpocketings of the synovial membrane of the knee joint
what is the function of the anterior cruciate ligament
limits anterior tibial displacements
- limits some internal rotation
- varus/valgus angulation in FULL EXTENSION
The ligaments ACL and PCL attach the — to the — to create a hinge joint called the knee
femur
tibia
what are the anterior and posterior cruciate ligaments
are 2 short, strong ligaments which criss-cross each other in the middle of the joint
ACL injuries are common in what sports
- football, basketball, soccer, gymnastics, volleyball, skiing
- more common in female than male soccer and basketball players
- primarily teens and early 20s
what is the mechanism of ACL injury
-cutting-deceleration-hyperextension
-most are non-contact
-60% have meniscal injury and medial collateral ligament injury
50% have subchondral bone injury –> DJD
what history is common with an ACL injury
-effusion and tenderness near patellar tenon/anterior tibial plateau
how do you measure stability of the ACL
measure the amount of excursion at end point
what other test should be performed for an ACL injury
- x-rays for avulsion fracture
- arthrogram
- MRI
- arthroscopy
how do you perform the drawer test
- patient supine and knee at 90 degrees flexion
- stabilize the proximal and distal segment
- grab the leg at the proximal tibia and pull towards you
why are 50% of drawer test a false negative
bc there may already be edema
how do you perform the Lachmann test
- patient supine and knee at 15 degrees flexion
- stabilize the proximal and distal segment
- grab the leg at the proximal tibia and pull toward you
- can standardize with a machine to measure displacement
what is a normal value for a KT-1000 test
> 3mm?
what % of Lachmann test are false positives
5-10%
what are the complications of ACL injury
- DJD associated with meniscal injury or avulsion
- instability increases likelihood of re-injury
- surgical intervention means long rehab
function of the posterior cruciate ligament
- limits posterior motion
- restricts external rotation
- keeps the tibia from moving too far posterior in relation to the femur (if the tibia moves too far posterior, the PCL can tear)
what is the # 1 cause of PCL injuries
auto accidents (right foot on break prior to impact)
what are other etiologies of PCL injuries
-sports due to direct blow to proximal tibia or hyperextension
what history is evident of PCL injury
“Pop” or no “pop”
No edema until 48 hrs
May bear weight
Reluctant to extend knee
what is seen upon examination of a PCL injury
- effusion variable bc of posterior muscle belly
- popliteal tenderness
- stability (much more stable than ACL injury)
- Sag test
- posterior drawer
what technique is used to test the posterior cruciate ligament
Sag test
how is the Sag test performed
- patient is supine as if sitting in a horizontal chair
- thighs at 90 degrees
- knees at 90 degrees
- examiner supports the legs by holding ankles and observes the sag as the tibial plateau sinks below patella
how is the posterior drawer and sag test performed
- patient supine and knee at 90 degree flexion
- stabilize the proximal and distal segment
- grab the leg at the proximal tibia and push away from you (tibia will move posterior)
- Sag test will be positive when you line up the knees even with each other, the injured side’s tibial tuberosity will not be even
what other diagnostic tools can be used to rest for PCL injury
x-ray for avulsion
MRI less accurate than ACL
arthroscopy (best diagnostic tool)
Fanelli, reports that the key to successful PCL reconstruction requires that the surgeon does what
- identifies and treats all pathology
- use of strong replacement grafts and materials is crucial
what is the medial collateral ligament
- deep layer is thickened capsule
- major medial stabilizer
what is O’Donahue’s Triad
- ACL
- MCL
- Medial Meniscus
MCL injuries are common in what sports
football and skiing
all MCL injuries involve what
- a blow laterally (except skiing, skating, etc.)
- very painful increasing over time
what history is common of a MCL injury
- struck from lateral side (football, soccer) or lateral to medial forces
- feels/hears a “pop”
- knee “stiffens up” within hrs
are partial or complete MCL tears more painful
partial (if all fibers are gone there is no pain)
what is evident upon examination of a MCL injury
- medial edema/minimal effusion
- medial ecchymosis if > 24 hrs old
- medial instability when stressed at 20 degree felxion
what is grade 1 MCL injury
no opening of medial joint
what is grade II of MCL injury
opens with firm end point
what is grade III of MCL injury
opens with soft end point
what test is performed for an MCL injury
varus/valgus stress test
how is a varus/valgus stress test performed
pt laying in supine position, hold ankle, apply force laterally to see if there is motion at the joint, then come around and apply force to the other side of the knee and apply medial force (valgus)