Knee Problems Flashcards
function of menisci
distribute load from convex femoral condyles to relatively flat tibial articular surfaces
which meniscus is fixed
medial
which meniscus is more mobile
lateral
which compartment does the knee pivot on
the medial compartment
function of MCL
resists valgus stress
function of LCL
resists varus stress
function of ACL
resists anterior subluxation of the tibia and internal rotation of the tibia in extension
function of PCL
resists posterior subluxation of the tibia (or anterior subluxation of the femur) and hyperextension of the knee
when do meniscal tears usually occur in younger people
sports injury
what accompanies 50% of ACL ruptures?
meniscal tear
how should you investigate ligament or meniscal tears?
MRI
which meniscus is more likely to tear?
medial (10x more likely)
why do meniscal tears have limited healing potential?
only the peripheral 1/3 has blood supply
which pattern of meniscal tear will not heal?
radial
what treatment should be considered in young patients with acute peripheral tears?
arthroscopic repair
what does an acute locked knee signify?
displaced bucket handle meniscal tear
how is a suspected bucket handle meniscal tear assessed clinically
heel height test
what treatment is given for bucket handle meniscal tear
urgent surgery - either arthroscopic repair or a partial menisectomy
what are degenerate meniscal tears a sign of?
early sign of OA
grade 1 ligament injury
sprain - some fibres torn but macroscopic structure remains in tact
grade 2 ligament injury
partial tear - some fascicles disrupted
grade 3 ligament injury
complete tear
features of MCL injury
usually heal well
not the case when combined with ACL or PCL rupture
treatment with knee brace, early motion and physio
which ligament is the main stabiliser against internal rotation of the knee
anterior cruciate ligament
can the ACL be repaired?
no it must be reconstructed
how is the ACL reconstructed
autograft from patellar tendon or hamstrings
allograft from achilles tendon
1/3 rule of ACL injury
1/3 compensate and are able to function well
1/3 can avoid instability by avoiding certain activities
1/3 do not compensate and have frequent instability meaning they will never return to high impact sport
what percentage of ACL ruptures end up having surgical reconstruction
40%
when do LCL injuries occur
excessive varus and hyperextension
relatively uncommon
will the lateral collateral ligament heal
no - can therefore cause varus and rotator instability
in what condition is there a high incidence of LCL injury
common peroneal nerve palsy
what commonly occurs in combination with LCL injury
PCL or ACL injury
what causes a PCL injury
direct blow to the anterior tibia, or a hyperextension injury
how does PCL injury present
popliteal knee pain and bruising
consequences of PCL injury
instability, recurrent hyperextension, feeling unstable going downstairs
what causes knee dislocation (not patellar)
serious, high energy injury
complications of knee dislocation
popliteal artery injury
nerve injury
compartment syndrome
what causes patellar dislocation
rapid turning or direct blow
risk factors for patellar dislocation
female adolescent ligamentous laxity valgus knee torsional abnormalities
in what percentage of people does patellar dislocation recur?
10%
what causes an extensor mechanism rupture
fall onto a flexed knee with quadriceps contraction
risk factors for extensor mechanism rupture
previous tendonitis steroid use chronic renal failure rheumatoid arthritis diabetes ciprofloxacin use
features of haemarthrosis
usually warm
generalised pain
swelling within an hour
usually associated with ACL rupture or fracture
features of effusion
develops over a period of 24hr
associated with meniscal or chondral injury
what is osteochondritis dissecans
atraumatic cartilage defect which occurs when an area of the surface of the knee loses its blood supply and the cartilage +/- bone can fragment off
what happens during cartilage healing
healing is with fibrocartilage rather than hyaline cartilage which has greater friction and less wear resistance
name 4 cartilage regeneration techniques
drilling/microfracture
osteochondral autograft/allograft
mosaicplasty
MACI - membrane induced autologous chondrocyte implantation
which cartilage regeneration technique is simplest and cheapest
microfracture
which cartilage regeneration technique is used for larger defects/bone loss
osteochondral allograft
predisposing factors to OA
articular cartilage injury, fracture, joint instability, genu varum/valgus, fracture malunion, degenerate meniscal tear, infection
when is knee replacement done
older patients with end stage arthritis
how long are new knees expected to last
15-20yrs
what is injured in the unhappy triad
ACL, medial collateral ligament and medial meniscus
typical mechanism of injury in meniscal tear
twisting force on a loaded knee
when may pseudo locking occur
arthritis
how do ACL injuries occur
high rotational force, turning upper body laterally on a planted foot
joint line tenderness
feature of meniscal tear
assessed by Steinmanns test
patterns of meniscal tear
longitudinal, radial, oblique and horizontal
what may large longitudinal tears result in
bucket handle tear - means a large meniscal fragment is able to displace anteriorly or into the intercondylar notch
examination findings ACL rupture
knee swelling
excessive anterior translation of the tibia on the anterior drawer/Lachman test
when do osteochondral/chondral injuries occur
impact or shear of articular surface or due to a direct blow
how should injuries involving large osteochondral fragments with a substantial portion of bone be fixed
fixed with pins
how should injuries involving non-weight bearing areas be treated
arthroscopic removal
how may the patellar or quadriceps tendon rupture
rapid contractile force which can occur after lifting a heavy weight, after a fall or spontaneously in a severely degenerate tendon
who tends to be affected by patellar tendon rupture
younger patients (
who tends to be affected by quadriceps tendon rupture
older patients (>40)
what is patellofemoral dysfunction
disorders of the patellofemoral articulation which results in anterior knee pain
what may also occur when the patella dislocates
medial patellofemoral ligament tear and osteochondral fracture
lipohaemarthrosis
