Lecture 7 - Knee Flashcards
what bones make up the true knee joint
Tibio-femoral joint is formed by
- femur (condyles)
- tibia (tibial plateau)
Movements at the knee joint
- flexion
- extension
- internal rotation (tibia)
- external rotation (tibia)
muscles that make up the quad
- rectus femoris
- vastus lateralis
- vastus medialis
- vastus intermedius
muscles that make up the hamstring
- semitendinosus
- semimembranosus
- bicep femoris
what muscle unlocks the knee
popliteus
pes anserine
acts as a secondary valgus restrainer, augmenting the medial support of the knee
* muscles that are attached to the pes anserine are the:
- gracillis
- sartorius
- semitendiosus
Ligaments of the knee
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
- Medial collateral ligament (MCL) most commonly injured
- Lateral collateral ligament (LCL)
what is joint line tenderness (JLT)
physical examination test commonly used to screen for sensitivity related to meniscal injuries
lateral meniscus
Lateral meniscus
- almost circular
- consistent in width throughout
- more mobile
- anterior end attaches to intercondyloid portion of tibia, behind ACL (blends with ACL)
- posterior end
posterior ends attaches to intercondyloid portion of the tiba
role of meniscus
increase joint congruency; act like a suction cup
- some cushioning effects
medial meniscus
- more like a half moon/semicircular fibrocartilage band
- bigger
- anterior portion is attached to the lateral meniscus via the transverse ligament
- attached to the tibia via meniscotibial ligaments
- posterior end attaches between the PCL and lateral meniscus
epidemiology of knee injuries
- 40% are ligamentous injuries
- most common injury is MCL, followed by patellar tendon, ACL, meniscus, LCL, then PCL
- females more commonly injure their knees compared to males
Steps of initial examination of the knee
History
- previous injury knee injury? MOI; does it feel the same as last time you injured it
Observation
- deformity, swelling (swipe test), discolouration
ROM
- active, passive, resisted
Manual muscle testing
Palpations
- point tenderness of ligaments may be a good indicator of which structures are injured
Special tests
Functional assessments
mechanism of an ACL sprain/tear
hyperextension, plant and twist (sounds like a loud snap/pop)
S/S of an ACL sprain/tear
- pain (depends on the degree) location can be: posterior, below the patella, lateral/anterior, extreme
- swelling (in first 24hrs; consider middle genicular artery)
- decreased ROM and strength (depends on the degree)
- altered gait
- feels very unstable
- hamstring goes into spasm with this injury; hanstring goes into protection mode and helps the tibia to not translate anteriorly
mechanism of an MCL sprain/tear
valgus force (intrinsic/extrinsic), tibial rotation force
S/S of MCL tear/sprain
- medial knee joint pain
- pain with full extension/flexion
- mild inflammation/swelling
- decreased strength/ROM
- altered gait patterns
- feeling unstable medial
why do quads atrophy when you tear your ACL
arthrogenic muscle inhibition (AMI) at the cortico level (brain tells muscle to do this)
- AMI is defined as a lack of extension due to quadriceps inhibition and hamstring contracture
mechanism of a meniscal tear
landing and twisting, planting and twisting (foot fixed); sometimes hear a tearing noise
S/S of a meniscal tear
- pain with weight bearing
- catching or clicking noise
- locking or give out of knee
- altered gait pattern
- swelling (minor/sever; depending on tear)
mechanism of an LCL sprain/ter
varus force (intrinsic/extrinsic), tibial rotation force
S/S of LCL sprain/tear
- lateral knee joint pain
- pan with full extension or flexion
- mild inflammation/swelling
- decreased strength/ROM
- altered gait pattern
- feeling unstable laterally
why is there more instability when you tear the LCL then when you tear your MCL
there aren’t as many muscles attaching to the lateral aspect of the knee (consider the pes anserine)
mechanism of a PCL/Posterior capsule sprain/teat
landing with knee extended, extrinsic force causing hyperextension
S/S of PCL/Posterior capsule sprain/tear
- posterior knee pain
- posterior swelling
- pain with full extension
- decreased strength and ROM
- poor control of hamstring preventing extension
what tests you use to test for injuries/sprains/tears of knee structures
ACL - anterior drawer test
PCL - Posterior drawer test
MCL - valgus challenge
LCL - varus challenge
Meniscus - Thessaly’s
what are the injuries that make up the unhappy (terrible) triad and why is this injury bad
Medical meniscus tear
MCL tear
ACL tear
- can cause tibio-femoral separation (like a door hinge)
how do you manage an unhappy triad injury
- RICE
- taping and bracing
- ROM
- strengthening
- balance
- functional/sport specific exercises
- RTP
what is a check rein
reinforced taping to prevent movement
is knee taping or knee bracing more effective
bracing
what to do if we suspect a knee fracture
OTTAWA KNEE RULE
x-ray knee if…
- bone tenderness with palpation of the head of the fibula
- isolated bony tenderness of the patella
- inabillity to flex knee to 90 deg
- 55 or older
- inability to weight bear for 4 steps immediately and in ED
why do we use ottawa knee rule
- evidence suggests useful to rule out fracture
- sensitivity of 98.5%
*decreases unneeded x-rays and saves time
WE DON’T WANT TO MISS FRACTURES
