knee Flashcards
what does turbid knee effusion suggest?
gout, infection
what does straw colored knee effusion suggest?
ra
what does clear knee effusion suggest?
normal
RA
which view is the best to visualise loss of medial joint space?
rosemberg view (30-40deg flexed weight bearing view with XR beam tilted caudally to profile joint line)
WBC raised: gout or RA?
Gout
normal foot progression angle
6-10 deg externally rotated
intoeing foot progression angle
negative 20-30 deg
describe the physiological evolution of leg alignment at various ages
0-18 months: genu varus
- tibial intorsion
2-6 years: genu valgum
- laxity of ligaments
- valgus max at 4yo
- management: reassure parents and measure child intermalleolar distance every 6 months
6-7 yo: straight
- tightening of ligaments
- operative correction advised if marked deformity persists past 10 yo
- note: slight valgus of 5-7 deg is normal
define rickets
failure of mineralisation of physes or bone due to vit D deficiency
define blount’s disease
infantile growth disorder with idiopathic arrest of growth plate on medial side of tibia
presentation of blount’s disease
- progressive genu varum + medial rotation of tibia
- often bilateral
mechanism of intoeing in CHILD
hip: femoral anteversion
- excessive internal rotation
- usually bilateral
- history of W sitting
management of intoeing in child
- conservative: cross legged sitting
- surgical when intoeing interferes with walking/running > derotational osteotomy
mechanism of intoeing in toddler
leg: medial tibial torsion
- commonest cause of bow leggedness in 1yo
mechanism of intoeing in infant
foot: metatarsus adductus (curved foot)
consequence of genu valgus (accept valgus till about 5-7yo)
- inhibition of lateral growth plate > OA of lateral compartment
- callosities
knee deformity seen in RA
genu valgum
knee deformity seen in OA
genu varum
symptoms in osteochondritis dissecans
- locking (loose body)
- giving way
- intermittent ache or swelling
exact site usually affected by osteochondritis dissecans
lateral part of medial femoral condyle
- wilson’s sign: pain when knee flexed 90, internal rotation, gradually straightened
management of osteochondritis dissecans
1) conservative: lifestyle modification (decrease activity)
2) surgery for unstable fragments
- small fragments: arthroscopic removal of fragment
- large fragments (>1cm): fixation with pins or herbert screws
causes of loose body in knee
1) trauma
2) OA
3) synovial chondromatosis
4) charcot’s joint
causes of charcot’s joint
1) diabetes
2) peripheral neuro
3) tertiary syphillis
4) tabes dorsalis
5) syringomyelia
6) myelomeningocele
7) cauda equina
differential diagnosis for anterior knee pain
- osteochondritis dessicans (young male, post trauma)
- patella maltracking > CMP (esp young females)
- patella subluxation
- patella tendinosis (jumper’s knee)
- plica syndrome
- hoffa syndrome: inflammation of infra patellar fat pad
management of osgood schlatter’s disease
conservative
- ice
- NSAIDs (pain relief + reduce inflamm)
- rest
- physiotherapy (quadriceps strengthening > reduce tension on tibial tuberosity)
- orthotic devices (brace)
etiology of acute joint swelling
1) haemarthrosis (trauma - ACL!/bleeding dyscrasias)
2) acute septic arthritis
3) gout/pseudogout
differentials for swelling at back of knee
1) skin
- lipoma
- sebaceous cyst
2) artery
- popliteal artery aneurysm
3) vein
- saphena varix
- dvt
4) nerve
- neuroma
5) enlarged bursae
- semimembranosus bursae
6) cyst
- baker’s cyst (associated with OA)
- popliteal cyst
what is a baker’s cyst
posterior herniation of knee joint capsule
what conditions is a baker’s cyst associated with?
- OA
- RA
- charcot’s joint
TRO dvt
signs of baker’s cyst
- swelling BELOW joint line (semimembranosus bursa is above)
- fluctuant
- may be transilluminable
- non tender
- positive slip sign
complications of baker’s cyst
- increased risk of dvt
lateral deviation of popliteal vein > compression> venous stasis
investigation of baker’s cyst
U/S
popliteal cyst vs semimembranous cyst
popliteal cyst empties on flexion of knee joint, semimembranosus cyst does not
risk factors for patella maltracking
1) malalignment of extensor mechanism/weakness of VMO
2) tight lateral retinaculum/ITB
3) lax/torn MPFL
4) large Q angle
causes of increased Q angle
1) genu valgum
2) femoral anteversion
3) external tibial torsion
4) laterally positioned tibial tuberosity
5) tight lateral retinaculum
6) larger pelvis
why is q angle not accurate in extension
laterally dislocated patella > false impression that Q angle is normal
management of patellofemoral overload
1) conservative
- analgesics
- physiotherapy: strengthen VMO, stretch ITB
- taping/knee brace
2) surgery
- lateral retinacular release
- anteromedial tibial tuberosity transfer
associated injuries/complications of tibial plateau fracture
- compartment syndrome (esp type 5 and 6)
- popliteal artery injury
- ligament/meniscal tear (contralateral side)
- malunion
- joint stiffness
- secondary OA
classification for tibial plateau fractures
schatzker’s classification
describe the types of tibial plateau fractures according to schatzker’s classification
1: simple split of lateral condyle
2: split of lateral condyle with more central area of depression
3: depression of lateral condyle with intact rim
4: fracture of medial condyle
5: fractures of both condyles but central portion of metaphysis still connected to tibial shaft
6: combined condylar and subcondylar fracture (split extending to metaphysis)
management of tibial plateau fractures by fracture type
lateral condylar fracture undisplaced/minimally displaced: conservative
- aspirate haemarthrosis + compression bandage > hinged cast
lateral condylar fracture markedly displaced/comminuted
- ORIF (plate + screws)
medial condylar fracture
- ORIF +/- lateral ligament repair
bicondylar fracture
- ORIF
osteoporotic condylar fracture
- ORIF or TKR
types of patellar fractures
1) undisplaced crack
2) comminuted/stellate
3) transverse fracture with gap between fragments
mechanism of injury for undisplaced patellar crack
direct blow
mechanism of injury for comminuted/stellate patellar crack
fall or direct blow in front of kidney
mechanism of injury for transverse fracture with gap
indirect traction injury due to forced, passive flexion of knee while quads muscle contracted
- torn extensor mechanism
- inability to actively extend knee
main complication of patella fractures
PFOA
management of patellar fractures
aim for early ROM for all
1) undisplaced/minimally displaced crack
- aspirate haemarthrosis
- protection with plaster cylinder holding knee extended
2) comminuted fracture
- aspirate haemarthrosis
- acceptable displacement: backslab
- severe displacement: complete/partial patellectomy
3) displaced transverse fracture
- ORIF: tension band wiring + K wires
- repair extensor tendons
common position preceding patellar dislocation
sudden contraction of quadriceps while knee stretched in valgus + external rotation
management of first instance of patellar dislocation
reduction + backslab + physiotherapy
risk factors for recurrent patella dislocation
1) generalised ligamentous laxity
2) underdevelopment of lateral femoral condyle
3) maldevelopment of patella (too high/small/lateral
4) genu valgus
5) tibial tubercle malalignment
6) primary muscle defect
7) more common in girls
management of recurrent patella dislocation
1) conservative
- reduction & backslab
- physiotherapy: isometric quad strengthening exercises (focus on vastus medialis to counterbalance lateral tilt/subluxation)
2) surgical
- repair patellofemoral ligaments
- realignment of extensor mechanism
- lateral release if lateral retinaculum too tight
complications of knee dislocation
1) early
- vascular injury: popliteal artery
- nerve injury: posterior tibial, common peroneal nerves
- capsular/meniscal injuries
- compartment syndrome
2) late
- reperfusion injury
- joint instability
- joint stiffness
management of knee dislocation
1) conservative
- quadriceps muscle exercises
2) surgery
- reduction + backslab in 15deg flexion
- unstable or vascular repair: external fixator
stabilisers of the knee
1) strong capsule
2) intraarticular ligaments: ACL, PCL
3) extraarticular ligaments: MCL, LCL
4) quadriceps
what is the unhappy triad (o’donoghues triad)
ACL + MCL + medial meniscus
note: classically described as MCL + medial meniscus but can be any collateral ligament + meniscal injury
grades of ligamentous sprain in knee
grade 1:
- ligament mildly damaged
- slightly stretched but able to keep knee joint stable
- PCL step off 0-5mm
grade 2:
- partial tear of ligament
- stretched to the point where it becomes loose
- PCL: 5-10mm of posterior translation
grade 3:
- complete tear of ligament
- knee unstable
- PCL: >10mm of posterior translation
management of ligamental injury of knee
1) conservative
- aspirate haemarthrosis
- pain relief: ice packs/nsaids
- physiotherapy: strengthen hamstrings & quads
2) surgical
- ACL reconstruction by grafting (hamstring/bone-patella tendon- bone)
indications for conservative management in knee ligament injuries
1) sprains & partial tear
2) isolated MCL, LCL, PCL tears
3) isolated ACL in non-sportsman
function of ACL
1) prevent anterior translation of tibia on femur
2) resist internal rotation of tibia
name the two bundles of the ACL
1) anteromedial > taut in flexion
2) posteriolateral > taut in extension
mechanism of acl injury
1) internal rotation on hyperextended knee
2) indirect varus blow to knee
- patients with greater Q angle > greater chance of ACL tear
history in acl injury
1) audible pop
2) giving way > inability to continue activity
3) immediate haemarthrosis
why does ACL not have ability to heal
1) synovial fluid keeps both ends apart
2) synovial fluid produces proteolytic enzymes exacerbating damage
3) synovial fluid prevents formation of fibrin platelet clot at wound site
mechanism of injury of PCL
- dashboard injury
mechanism of injury of LCL
varus force
mechanism of injury of MCL
valgus force
why is medial meniscus more commonly injured than lateral
1) medial meniscus LESS mobile (due to attachment of MCL)
2) popliteus muscle pulls lateal meniscus into more favourable position during suden movements
etiology of meniscal pain
synovitis; not due to innervation of meniscus
symptoms of meniscal tear
1) severe pain over joint line
2) knee locked in partial flexion
3) delayed swelling (unlike ligament tear)
4) giving way
what is locking of knee suggestive of?
bucket handle tear of meniscus
management of meniscus injury
aim for meniscus preservation
1) conservative
- analgesia
- physiotherapy
- glucosamine + supplements (controversial but can offer)
- bracing + orthosis
- H&L injections, PRP
2) surgery
- microfracture therapy
- menisectomy (outer 1/3: good vascular ss from capsule > attempt repair; mid 1/3: intermediate vascular ss and healing; inner 1/3 avascular and poor healing > total/subtotal menisectomy)
- cartilage work (scaffold/implants)
what type of collagen is articular cartilage of meniscus made of?
type II collagen
risk factors for patella/quadriceps tendon rupture
- DM
- SLE
- RA
- streroid use`
blood supply of ACL
medial geniculate artery
lateral meniscus or medial meniscus more associated with ACUTE ACL tear
lateral meniscus
outerbridge classification of cartilage lesions
grade 1: chondromalacia
grade 2: fibrillation <1/2
grade 3: fragmentatino to subchondral bone
grade 4: erosion to bone
