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MSK > disorders of the knee > Flashcards

disorders of the knee Flashcards

1
Q

in a femoral shaft fracture what muscles cause the proximal fragment to abduct and flex

A

abduct -pull of gluteus medius and minimus on the greater trochanter
flex- due to action of iliopsoas on lesser trochanter

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2
Q

in a femoral shaft fracture what muscles cause the distal fragment to adduct and extend

A

adduct - adductor muscles (adductor Magnus, gracilis )

extend- pull of gastrocnemius on the posterior femur

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3
Q

causes of femoral shaft fracture

A

high velocity trauma
fall from height
road traffic collision

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4
Q

causes of distal femoral fractures

A

high energy sporting injury in younger patients

elderly - seen in association with osteoporotic bone. usual mechanism is fall form standing.

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5
Q

describe tibial plateau fractures

A

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

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6
Q

what are the causes of a patellar fracture

A

direct impact injury - e.g knee against dashboard

eccentric contraction of quadriceps (muscle is contracting but joint is extending)

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7
Q

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)

A

patient will be unable to perform a straight leg raise

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8
Q

causes of patella dislocation

A
  • 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.
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9
Q

factors that can predispose to patellar dislocation

A
  • generalise ligamentous laxity (looseness )
  • weak quads, especially then VMO
  • long patellar ligament
  • previous dislocations
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10
Q

treatment for patellar dislocation

A

extend knee and manually reduce the patella.

immobilisation is used whilst healing takes place and this is followed by physiotherapy to strengthen the VMO.

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11
Q

cause of meniscal injury

A

sudden twisting motion of a weight bearing knee in a high degree of flexion

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12
Q

how patient would describe meniscal injury

A

intermittent pain, localised to joint line
knee clicking, catching , locking
sensation of giving way
swelling is a delayed symptom

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13
Q

why is acute haemarthrosis rare in a meniscal injury and if it does occur what does it indicate

A
  • menisci are largely avascular

- indicates tera in the peripheral vascular aspect of meniscus or and an associated injury to ACL.

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14
Q

a chronic effusion can occur in meniscal injuries. what is a chronic effusion

A

increased synovial fluid due to synovitis

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15
Q

how does meniscal injuries present on examination

A

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.

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16
Q

how is meniscal injury treated

A

acute traumatic meniscal tera - meniscectomy or meniscal repair
chronic - conservative management

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17
Q

what causes a collateral ligament injury

A

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.

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18
Q

why does a torn lateral collateral ligament cause more knee instability than MCL

A

because the medial tibial plateau forms a deeper and more stable socket for the femoral condyle than the lateral tibial plateau.

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19
Q

what is the unhappy triad

A

injury to anterior cruciate ligamanet, medial collateral ligament and medial meniscus

20
Q

how is the unhappy triad caused

A

strong force applied to the lateral aspect of the knee.

21
Q

what causes the anterior cruciate ligament to tear

A

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.

22
Q

how will a patient describe a tear in the ACL

A

popping sensation
immediate swelling
knee giving way-instability of the knee as tibia slides anteriorly under the femur

23
Q

what is anterolateral rotatory instability

A

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’.

24
Q

how is ACL injury treated

A

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.

25
Q

how is injury caused to the posterior cruciate ligament

A

dashboard injury

  • knee flexed and large force applied to the upper tibia displacing it posteriorly
  • when football player falls on flexed knee with ankle plantar flexed, tibia hits ground first and is displaced posteriorly tearing the PCL.
26
Q

how can ACL &PCL injury be detected

A

anterior and posterior drawer test

lachman’s test for ACL only

27
Q

cause of dislocation of knee

A

high energy trauma

at least 3 of 4 ligament must be ruptured (ACL, PCL ,MCL, LCL)

28
Q

why is an associated arterial injury common in knee dislocation

A

popliteal artery is tethered proximally when it enters popliteal fossa at the adductor hiatus and vitally where it exits the popliteal fossa by passing under the tedious arch of the soleus muscle.

29
Q

what type of swelling can occur around the knee

A

bony
soft tissue - enlarged popliteal lymph node, popliteal artery aneurysm
fluid - inside joint=effsuion. outside joint = soft tissue haematoma.

30
Q

what is an effusion

A

accumulation of fluid inside the knee joint.
`acute if less than 6 Hrs after injury or delayed if more than 6 hours after injury.
delayed swelling is usually due to reactive synovitis.

31
Q

what are the two divisions of acute knee effusions

A

haemarthrosis- blood in the joint. ACL rupture until proven otherwise.
lipo-haemarthrosis- blood and fat in the joint. fracture until proven otherwise asa the fat is usually released from the bone marrow.

32
Q

what is known as housemaid’s knee

A

prepatellar bursitis

knee pain , swelling , may be erythema overlying the inflamed bursa. cant kneel on affected side.

33
Q

what is known as clergyman’s knee

A

infrapatellar bursitis

due to repeated microtruma caused by activities involving kneeling.

34
Q

causes of a knee effusion

A 
OA 
rheumatoid arthiritis 
infection 
gout and pseudogout 
repetitive microtrauma to the joint
35
Q

what is known as baker’s cyst /popliteal cyst

A

semimembranosus bursitis

swelling in popliteal fossa

36
Q

what is osgood-schlatter’s disease (OCD)

A

inflammation of the apophysis (\site of insertion ) of the patellar ligament into the tibial tuberosity.
patients complain of intense knee pain during running, jumping, squatting , ascending and descending stairs and during kneeling.
resolves with rest and ice.

37
Q

OA in knee symptoms

A

knee pain , stiffness and swelling
pain that comes and goes , pain precipitated by activities , worse after prolonged inactivity or rest.
-varus deformity(deviation of distal component towards midline)
-valgus deformity (deviation of distal component towards midline)
crepitus- due to loss of articular cartilage
knee giving way due to muscle weakness

38
Q

risk factors of OA in knee

A 
age 
female sex
previous trauma to joint 
obesity 
family history 
other conditions affecting the joint.
39
Q

treatment of OA in knee

A

1) strengthening exercises
2) analgesia, weight loss, activity modification
3) total knee replacement

40
Q

what is septic arthritis

A

invasion of the joint space by micro organism

41
Q

what is the most common pathogen causing septic arthritis

A

staphylococcus aureus

42
Q

risk factors of septic arthritis

A

extremes of age
diabetes mellitus
rheumatoid arthiritis
immunosuppression and intravenous drug abuse.

43
Q

what are the consequences of septic arthritis

A

damage to articular cartilage
neutrophils stimulate synthesis of cytokines and other inflammatory products resulting in hydrolysis of collagen and proteoglycans

44
Q

symptoms of septic arthritis of the knee

A

fever
pain
reduced range of movement

45
Q

what should u examine a knee joint for is septic arthritis is suspected

A

erythema
swelling
warmth
tenderness
imitation of active and passive range of movement
draining sinus is the most distinctive finding.

46
Q

what to do is septic arthritis if the knee is suspected

A

aspiration of the joint

send for urgent microscopy.

MSK (12 decks)

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