Knee Problems Flashcards
what is role of ACL
prevents abnormal internal rotation of tibia (twisting is either ACL or meniscal)
what is role of PCL
prevents hyperextension and anterior translocation of femur
what is role of MSL
resists valgus force
what is role of LCL
resists varus force
what have you injured if you get up from squatting
meniscal tear
what is a grade 1 knee ligament injury
sprain
tear some fibres but macroscopic structure intact
what is grade 2 knee ligament injury
partial tear
some fascicles disrupted
what is grade 3 knee ligament injury
complete tear
what surgery may help in younger patients with medial OA
osteotomy of proximal tibia (HTO) to shift load to lateral compartment
esp useful for heavy manual workers as knee replacement would fail early
when would knee replacement be considered and what are different kinds
patient with substantial pain and disability where conservative management no longer works
resurface all 3 compartments (total knee replacement) or partial knee replacement (UKR, or patellofemoral replacement)
what kind of knee replacement is failure incidence higher in
higher in partial since arthritis can progress in the unresurfaced compartments
by which movement will a meniscal tear occur
twisting force on loaded knee (eg turning at football, squatting)
what may a large longitudinal meniscal tear result in
bucket handle tear where a large meniscal fragment is able to flip out of its normal position and displace anteriorly or into the intercondular notch where the knee locks and if unable to fully extend due to obstruction from fragment
what is a degenerate tear
occurs as meniscus weakens with age - can be a horizontal, longitudinal or radial tear
how to tell difference between bucket handle tear and degenerate tear
degenerate will be steinmanns negative
what are the symptoms of a meniscal tear
patient localises pain to the medial (majority) or lateral joint line and effusion develops by following day
knee locking and feeling like it will give way
what is cause of knee locking in meniscal tear
15o or so block to full extension ie cant straighten properly = caused by significantly torn meniscus flipping over and becoming stuck in joint line
however, possible to not have this if torn meniscus not unstable enough to flip
what causes knee feeling like its going to give way in meniscal tear
if loose fragment is caught in knee when walking
what does an acute locked knee signify and what surgery does this urgently require
displaced bucket handle tear
arthroscopic repair
if irrepairable = needs menisectomy to unlock knee and prevent further damage
how is a meniscal tear diagnosed
clinical = effusion, joint line tenderness, pain on tibial rotation (steinmann’s test)
MRI will confirm suspicion
why are >90% of meniscal tears not suitable for repair
only blood supply in outer third of meniscus so limited healing
only fresh longitudinal tears involving outer 1/3 of meniscus in young patient should be considered
what is initial treatment
pain and inflammation may settle and knee may smooth off own meniscus
steroid injection in degenerate tears may help symptoms in early period
what happens if pain from acute tear do not settle within 3 months
arthroscopic partial menisectomy
why shouldn’t meniscectomy be considered in patient who also has OA
if degenerative xray (loss of joint space, sclerosis, osteophytes) or MRI (hyaline cartilage loss, bone marrow oedema) then the removal of meniscal tissue may increase stress on already worn / damaged surface
what force causes an ACL rupture
high rotational force, turning the body laterally on a planted foot leading to internal rotation on tibia
usually occurs at football, rugby, skiing etc
what are symptoms of ACL rupture
pop usually felt/heard and haemarthrosis (effusion due to bleeding in joint) within an hour
chronically = rotatory instability with knee giving way on planted foot
what is found in clinical examination of ACL rupture
knee swelling (haemarthrosis or effusion) with excessive anterior translation of the tibia on the anterior drawer test and Lachman test
how is ACL rupture treated
physio, surgery if don’t respond
what % of primary repair of ACL need a reconstruction
40%
in what case would you progress straight to ACL reconstruction
professional sportsmen
those whose knees give way on sedentary activities
what does ACL reconstruction involve
tendon graft (usually patellar tendon or semitendonosis and gracilis autograft) being passed through the tibial and femoral tunnels at the usual location of ACL in knee and secured to bone
why is it known as a disease of 1/3rds in terms of complication
1/3 = compensate well
1/3 = manage by avoiding certain movements and sport
1/3 = do poorly with frequent giving way with normal activities
physio of quadriceps and hamstrings may help compensation
what force causes MCL rupture
valgus stress injury (ie rugby tackle from side)
higher forces may also damage ACL and risk lateral tibial plateau fracture
what is symptoms of MCL rupture
may have laxity and pain on valgus stress with tenderness over the origin or insertion of MCL
how is MCL treated
heals quite well
acute tears = hinged knee brace
chronic instability = MCL tightening (advancement), or reconstruction with tendon graft
what force causes PCL rupture
direct blow to anterior tibia with knee flexed (eg motorcycle crash) or hyperextension
when is PCL reconstruction performed
when reconstructing multiple ligament injured knee
when only time reconstruction of PCL rupture in isolation (not common) take place
only those with severe laxity and instability with frequent hyperextension or feeling unable descending stairs
reconstruction here usually with cadaveric achilles tendon allograft
what force causes LCL rupture
varus stress injury, can occur with or without injury to PCL
what other bad things can happen when you tear your LCL
high incidence of common peroneal nerve injury from excessive stretch
LCL injuries often part of multiple knee ligament injuries with high incidence of vascular injury (popliteal artery intimal or complete tear)
what is symptoms of LCL rupture
patients usually have marked instability on rotational movement (excessive external rotation of tibia and varus)
how is LCL ruptures treated
usually surgical with early repair or late construction with tendon graft
with higher degrees of force, some injuries can involve rupture or more than one of four knee ligaments, how do you treat this
surgical reconstruction (multiple ligament) due to degree of instability
complete knee dislocations should be reduced as emergency, why?
high incidence of neurovascular injury
as well as reduction, may require external fixation for temporary stabilisation
why are regular checks on the circulation of food mandatory after a complete knee dislocation
intimal tears can occur which later thrombose
what is an osteochondral / chondral injury and how do they occur
injury to articular cartilage +/- the bone underneath it
occur due to impaction or shear of the articular surface
or due to direct blow
when would osteochondral / chondral injury be suspected
ongoing pain and effusion after a knee injury warrant further investigation with xray, MRI and with arthroscopy
how is osteochondral / chodral injury treated
acute involving large osteochondral fragments with substantial bone should be fixed with pins
if they are from non-weight bearing area or have little bone attached they are usually removed arthroscopically
what type of cartilage fills a defect in surface of knee
fibrocartilage (scar type hyaline cartilage) not as good as hyaline
what is microfracture
process where by if a defect has bare bone at its base it can be drilled to induce bleeding to promote fibrocartilage formation from stem cells differentiating into chondroblasts
what does the extensor mechanism of the knee constitute
tibial tuberosity patellar tendon patella quadriceps tendon quadriceps muscle
what can cause patellar tendon (<40 yo) or quadriceps tenon (>40 yo) rupture
rapid contractile force which can occur after lifting a heavy weight, after a fall or spontaneously in a severely degenerate tendon
what are the risk factors for extensor mechanism ruptures
history of tendonitis, chronic steroid use, diabetes, RA and chronic renal failure Quinolone antibiotics (eg ciprofloxacin) can cause tendonitis and risk tendon ruptures steroid injections for tendonitis of extensor mechanism should be avoided due to risk of rupture
how is extensor mechanism rupture diagnosed
straight leg test to determine if extensor mechanism intact
may also have palpable gap in extensor mechanism = may not be obvious in obese patients so US to determine extent of injury
xray = reveal high (PT rupture) or low lying (quads rupture) patella
how is extensor mechanism rupture treated
surgical with tendon to tendon repair or reattachment of tendon to patella
do not inject steroids!
what conditions does the term “patellofemoral dysfunction” cover
disorders of the patellofemoral articulation resulting in anterior knee pain
chondromalacia patellae (softening of hyaline cartilage)
adolescent anterior knee pain
lateral patellar compression syndrome
what are the risk factors for patellofemoral dysfunction
females (due to wider hips resulting in more lateral pull of quadriceps)
joint hypermobility
genu valgum
femoral neck anteversion
what are symptoms of patellofemoral dysfunction
anterior knee pain, worse going downhill, a grinding or clicking sensation at front of knee and stiffness after prolonged sitting
stiffness causes “pseudolocking” = acutely stiffens in flexed position
what is treatment of patellofemoral dysfunction
physio aimed at rebalancing quadriceps (esp vastus medialis)
taping may alleviate symptoms
surgery last resort - either releasing tight lateral retinaculum or if there is relatively lateralised tibial tubercle then a tubercle transfer to aid patellar tracking
what side does patella mostly always dislocate to
laterally
how to fix patella dislocation
may spontaneously reduce when knee straightened or rarely may require manual manipulation
what happens when patella dislocates
the medial patellofemoral ligament tears and osteochondral fracture may occur as the medial facet of the patella strikes the lateral femoral condyle
what is seen on xray in patellar dislocation
small opacification on xray (the osteochondral fracture)
lipo-haemarthrosis occurs which is also seen on xray
what % risk of recurrent dislocation after first time
10
how is patellar instability treated
risk of recurrence decreases with age and physio to strengthen quadriceps may help
if dislocation frequent = tibial tubercle transfer or medial patellofemoral ligament (MPFL) reconstruction may help
