Conditions Of The Knee And Surgery Flashcards
What side of the knee does OA most commonly affect?
What abnormalities does this cause?
Medial compartment
Valgus deviation of the leg
Outline the process of a total knee replacement
- vertical anterior incision made on the knee
- patella is rotated out of the way
- articular surfaces of the femur + tibia removed
- replaced by metal surfaces (cemented or uncemented)
- plastic spacer is added between the metal
Chemical VTE prophylaxis after total knee replacement
LMWH or aspirin
Presentation of septic arthritis
- acute red swollen joint
- warmth
- pain on movement
- temperature (not always)
What microorgnism organism can cause septic arthritis?
- Staphylococcus aureus (most common)
- neisseria gonorrhoea
- streptococcus pyogenes
- haemophilus influenza
- E. coli
Causes of septic arthritis
- surgery
- prosthetic joints
- knee effusion secondary to bacterial infection
- articular cartilage damage
Risk factors of septic arthritis
- increasing age
- pre-existing joint disease
- diabetes mellitus
- immunosuppresion
- CKD
- prosthetic joints
- IV drug use
Gold standard investigation of suspected septic arthritis
Joint aspiration
What should the joint aspiration fluid in suspected septic arthritis be sent off for?
- gram stain
- leucocyte count
- polarising microscopy
- fluid culture
What will joint aspiration of septic arthritis show?
Bacteria
Management of septic arthritis
- empirical IV abx until sensitivities are known
- flucloxacillin first line
- clindamycin if penicillin allergic
-
ceftriaxone if N.gonorrhoea
. - abx normally needed for 4-6 weeks (IV first for 2 weeks then oral)
. - joint irrigation + debridement
Complications of septic arthritis
OA + osteomyelitis
Causes of knee swelling
VITAMIN C+D
- Vascular: - haemarthrosis
- Inflammatory: bursitis
- Trauma: meniscal tear > baker’s cyst | fracture
- Autoimmune: RA
- Metabolic: gout/pseudogout
- Iatrogenic: infected prosthetic joint
- Neoplasia: rare
- Cancer: rare
- Degenerative**: OA
Name the 6 bursae of the knee
- suprapatellar bursa
- subcutaneous prepatellar bursa
- subcutaneous infrapatellar bursa
- deep infrapatellar bursa
- subsartorial bursa
- semimembranosus bursa
What bursa is inflamed in Housemaid’s knee?
How does this happen?
SC prepatellar bursa
Leaning forward on knee
What bursa is inflamed in Clergyman’s knee?
How does his happen?
SC infrapatellar bursa
Prolonged kneeling
What is bursa is involved in Baker’s/popliteal cyst?
Semimembranosus bursa
Cause of Baker’s cyst
Secondary to degenerative changes in the knee associated with:
- meniscal tears
- OA/RA
- knee injuries
Pathophysiology of a Baker’s cyst
- secondary to degenerative changes in the knee joint
- synovial fluid is squeezed out of the knee joint and collects in the popliteal fossa
Presentaion of Baker’s cyst
Localised to the popliteal fossa
- pain
- fullness
- pressure
- palpable lump or swelling
- restricted ROM if large
Examination findings of Baker’s cyst
- most apparent when pt standing with knee fully extended
- Foucher’s sign lump will get smaller when the knee if flexed at 45°
What is Foucher’ sign?
What is it seen in?
The lump of a Baker’s cyst will get smaller when the knee if flexed to 45°
Investigations of Baker’s cyst
USS
MRI to evaluate cyst before surgery
Management of Baker’s cysts
- no treatment if asymptomatic
- non surgical: modified activity, analgesia, PT, USS guided aspiration, steroid injections
- surgical: arthroscopic procedures to treat underlying knee pathology causing the cyst
What do you call fluid inside a joint vs outside a joint?
Inside - effusion
Outside - soft tissue haematoma
What are the two types of knee effusion?
What is suspected until proven otherwise in each case?
- haemarthrosis: blood in joint | ACL injury until proven over wise
- lip-haemathrosis: fat + blood in joint | fracture until proven otherwise
Name the four ligaments in the knee
Anteior cruciate ligament
Posterior cruciate ligament
Lateral collateral ligament
Medical collateral ligament
Mechanism of meniscal injuries
Twisting injury
Presentation of meniscal tears
- occurs during twisting movement of the knee
- pop sound or sensation
- pain
- swelling
- stiffness
- restricted ROM
- knee giving way
- locking of the knee
What are the two special tests of meniscal tears?
McMurray’s test
Apley grind test
What is McMurray’s test?
Whata is it used for?
- involves the pt lying supine
- examiner takes leg + flexes knee
- turn the foot inwards (internal rotation of tibia) + apply outwards pressure to the inside of the knee (varus pressure) extend the knee
- pain or restriction indicates lateral meniscal damage
. - External rotation of tibia + applying inwards pressure on the knee (valgus pressure) extend the knee
- pain or restriction indicates medial meniscal damage
What is the Apley Grind test?
What is it used for?
- patient lying prone + flexing knee to 90 with thigh flat on cough
- downward pressure applied to the thigh
- the tibia is internally + externally rotated at the same time
- pain indicates a positive result
- meniscal damage
What are the Ottawa knee rules used for?
To determine whether a patient requires an x-ray for the knee after an acute knee injury to look for a fracture
What are the Ottawa Knee rules?
A patient requires a knee x-ray if any of the following are present:
- age 55 or above
- patella tenderness (with no tenderness elsewhere)
- fibula head tenderness
- cannot flex knee to 90°
- cannot weight bear/limping
Imaging for meniscal damage
MRI scan first line
Arthroscopy is gold standard for diagnosing meniscal tear
Management of meniscal damage
- RICE
- NSAIDs
- Physiotherapy
- arthroscopy for repair or resection
What is a risk of arthroscopy resection of meniscus?
Often results in OA
Function of the ACL
Prevents anterior displacement of tibia relative to the femur
Function of PCL
Presents posterior displacement of tibia to relative femur
What is origin + insertion of the ACL?
From anterio-medial tibia (intercondylar eminence) to lateral condyle of femur
What is the origin + insertion of the PCL?
From the posterior lateral tibia to the medial condyle of the femur
Function of the medial collateral ligament
Resists valgus angulation (lateral pressure)
Function of the lateral collateral ligament
Resists varus angulation (medial pressure)
Mechanism of collateral knee ligament injury
Contact/direct blow e.g. sport
- if MCL: valgus strain
- if LCL: varus strain
Treatment of collateral ligament injury
- RICE
- Brace
- gradual return to activity
- analgesia
What special tests can be done to test ACL and PCL function?
Anterior + posterior drawer test
Lachman’s test
Presentation of ACL injury
- a twisting injury
- pain
- swelling
- pop sound or sensation
- instability
- tibia moves anteriorly to the femur > buckling
Investigations of cruciate ligament damage
MRI first line imaging
arthroscopy is gold standard Ix
Management of ACL injury
- RICE
- analgesia > NSAIDs
- crutches + knee braces
- Physiotherapy
- arthroscopic surgery to reconstruct the ligament
Describe ACL arthroscopic surgery
A new ligament is formed using a graft or tendon from another location
Such as hamstring tendon, quadriceps tendon, bone-patellar tendon-bone
Mechanism of PCL injury
Falls
Hyperextension
What is the unhappy triad?
ACL
Medial collateral ligament
Medial meniscus
What is Osgood Schlatter disease?
Inflammation at the tibial tuberosity where the patella tenon inserts (apophysis)
Common cause of anteior knee pain in adolescents
Pathophysiology of osgood schlatter disease
- Multiple minor avulsion fractures at the apophysis of the patella ligament into the tibial tuberosity
- this causes growth of the tibial tuberosity > visible lump below the knee
- initially the lump is tender but as it heal, the lump becomes hard and no tender
Presentation of osgood schlatter disease
- gradual onset of symptoms
- visible or palpable hard + tender lump at tibial tuberosity
- pain in anterior knee
- pain worsened by activity, kneeling or extension of knee
Management of osgood schlatter disease
- reduction in physical activity
- ice
- NSAIDs
- stretching + physio once symptoms settle
What structure helps prevent patella dislocation?
Vastus medialis obliquus
What is the function of Vastus medialis obliquus?
- stabilise patella in trochlea groove
- control tracking in flexion + extension
- prevents patella dislocation
Mechanism of patella dislocation
- twisting action in slight flexion
- trauma
- direct blow to knee
What factors predispose a patella dislocation?
- previous dislocation
- long patella ligament
- shallow trochanter groove
- ligament laxity
- weakness of Vastus medialis obliquus
Management of patella dislocation
- reduce + immobilise
- knee brace
- analgesia
How do you check for a patella fracture?
Ask patient to raise a straight leg
Inability is indicative of patella fracture
Mechanism of action of tibial plateau fracture
- High energy trauma e.g. RTC or fall from height
- due to impaction of femoral condyle onto tibial plateau
- normally varus force > lateral tibial plateaus is more often fractured
What side is most commonly damaged in tibial plateau fractures and why?
Lateral tibial plateau due to varus strain
Presentation of tibial plateau fracture
- sudden onset pain in knee
- inability to weight bear
- swelling
- tenderness
Investigations of tibial plateau fractures
X-ray AP + lateral
CT scan
Management of tibial plateau fracture
- non-operative management: hinged knee brace, reduce weight bearing, PT, analgesia
- surgical management: open reduction + internal fixation
Mechanism of action of patella fracture
- Direct trauma to the patella (most common)
- as a result of rapid eccentric contraction of quads
Presentation of patella fracture
- anterior knee pain
- worse with movement
- inability to raise straight leg
- swollen + bruised
What is bipartite patella?
A congenital condition where there is failure of patella fusion > two separate bones
Asymptomatic + is picked up incidentally on imaging
What classification is used for patella fractures?
What are they?
AO foundation classification
- extra-articular or avulsion
- partial articular
- complete articular
Management of patella fractures
- open reduction + internal fixation with tension band wiring
- brace
- analgesia
Investigations of patella fracture
X-ray in AP, lateral + skyline views
What is a Hoffa fracture?
- A specific type of type B partial articular distal femoral fracture
- a fracture of posterior aspect of femoral condyle in coronal plane
- more often affects lateral condyle
Presentation of distal femoral fracture
- severe pain in distal thigh
- inability to weight bear
- swelling + bruising
Management distal femur fracture
- if there is significant malalignment > initial realignment in A&E then immobilisation
- if more proximal extra-articular: retrograde nailing
- if more distal intra-articular: ORIF with distal femoral plate
How does the location of a distal femoral fracture affect the surgical treatment given?
- if more proximal extra-articular: retrograde nailing
- if more distal intra-articular: ORIF with distal femoral plate
Complications of distal femoral fracture
- Malunion
- Non-union
- Secondary OA
- Compartment syndrome
- Haemorrhage
What is the most common cause of lateral knee pain in athletes?
Iliotibial band syndrome
What is Iliotibial band syndrome?
- inflammation of the Iliotibial band/tract
What is the Iliotibial band/tract?
A branch of fibres that form the shared aponeurosis of tensor fasciae lactate and gluteus maximus
Risk factors of Iliotibial band syndrome
- Regular exercise involving repetitive flexion + extension e.g. runners
- foot pronation
- hip adbuctor weakness
Presentation of Iliotibial band syndrome
Lateral knee pain worsened by exercise
What special tests can be used for ilitiotibal band syndrome?
Nobles test
Renne test
Management of Iliotibial band syndrome
- modified activity
- analgesia
- steroid injections
- Physiotherapy
- surgery only indicated is symptomatic for 6 months > release of Iliotibial band from attachments > allows greater ROM
Why are knee dislocations serious injuries?
Popliteal artery and common peroneal nerve are in close proximity
