disorders of the knee Flashcards
in a femoral shaft fracture what muscles cause the proximal fragment to abduct and flex
abduct -pull of gluteus medius and minimus on the greater trochanter
flex- due to action of iliopsoas on lesser trochanter
in a femoral shaft fracture what muscles cause the distal fragment to adduct and extend
adduct - adductor muscles (adductor Magnus, gracilis )
extend- pull of gastrocnemius on the posterior femur
causes of femoral shaft fracture
high velocity trauma
fall from height
road traffic collision
causes of distal femoral fractures
high energy sporting injury in younger patients
elderly - seen in association with osteoporotic bone. usual mechanism is fall form standing.
describe tibial plateau fractures
high energy injury
usual mechanism is axial loading with virus/ valves angulation of the knee
fracture affects articulating surface of the tibia within the knee joint. can be unicondylar or bicondylar.
articular cartilage is always damaged
what are the causes of a patellar fracture
direct impact injury - e.g knee against dashboard
eccentric contraction of quadriceps (muscle is contracting but joint is extending)
if the extensor mechanism is disrupted in a patellar fracture how will this present in examination (i.e the fracture completely splits the patella distal to the insertion of the quadriceps tendon)
patient will be unable to perform a straight leg raise
causes of patella dislocation
- trauma
- twisting injury in slight flexion or a direct blow to the knee
- athletic teenagers are most affected
- usual mechanism is internal rotation of femur on a planted foot whilst flexing knee.
factors that can predispose to patellar dislocation
- generalise ligamentous laxity (looseness )
- weak quads, especially then VMO
- long patellar ligament
- previous dislocations
treatment for patellar dislocation
extend knee and manually reduce the patella.
immobilisation is used whilst healing takes place and this is followed by physiotherapy to strengthen the VMO.
cause of meniscal injury
sudden twisting motion of a weight bearing knee in a high degree of flexion
how patient would describe meniscal injury
intermittent pain, localised to joint line
knee clicking, catching , locking
sensation of giving way
swelling is a delayed symptom
why is acute haemarthrosis rare in a meniscal injury and if it does occur what does it indicate
- menisci are largely avascular
- indicates tera in the peripheral vascular aspect of meniscus or and an associated injury to ACL.
a chronic effusion can occur in meniscal injuries. what is a chronic effusion
increased synovial fluid due to synovitis
how does meniscal injuries present on examination
joint line tenderness
restricted motion due to pain and swelling
mechnical block to motion or locking can occur due to loose meniscal fragments becoming trapped between the articular surfaces.
how is meniscal injury treated
acute traumatic meniscal tera - meniscectomy or meniscal repair
chronic - conservative management
what causes a collateral ligament injury
acute varus/valgus angulation of the knee
varus= medial angulation of the knee straining the lateral collateral ligament
valgus- lateral angulation of the knee straining medial collateral ligament.
why does a torn lateral collateral ligament cause more knee instability than MCL
because the medial tibial plateau forms a deeper and more stable socket for the femoral condyle than the lateral tibial plateau.
what is the unhappy triad
injury to anterior cruciate ligamanet, medial collateral ligament and medial meniscus
how is the unhappy triad caused
strong force applied to the lateral aspect of the knee.
what causes the anterior cruciate ligament to tear
sudden deceleration, hyperextension or rotational injury
non contact injury - no other players involved.
also can be torn by application of large force to the back of the knee when the joint is partly flexed.
how will a patient describe a tear in the ACL
popping sensation
immediate swelling
knee giving way-instability of the knee as tibia slides anteriorly under the femur
what is anterolateral rotatory instability
when ACL is torn rotation of tia occurs with PCL as the centrally located axis. the medial tibial condyle rotates internally and the lateral tibial condyle sublimes anteriorly but then the lateral tibial condyle reduces with a sudden slip. this creates a sudden sensation f the knee ‘giving way’.
how is ACL injury treated
for patients with low functional demand of knee they can function well without ACL by using musculature to stabilise joint but for sportman and very active people surgical reconstruction will be needed.
