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MSK Clinical Conditions > Conditions Of The Knee > Flashcards

Conditions Of The Knee Flashcards

1
Q

What are the possible causes of femoral shaft fractures in different patient groups? 1️⃣

A

Young children:

  • high velocity trauma e.g fall from height, road traffic collision
  • non-accidental injury (abuse)

Young adults:
-high velocity trauma

Elderly w/ osteoporotic bones or patients with bone metastases/lesions:
-Low velocity injury e.g falling over

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2
Q

How does the musculature act as a deforming force after a femoral shaft fracture? 1️⃣

A

Proximal fragment:

  • often abducted due to pull of gluteus medius and minimus on greater trochanter
  • flexed due to action of iliopsoas or lesser trochanter

Distal fragment:

  • adducted into varus deformity due to action of adductor Magnus and gracilis
  • extended due to pull of gastrocnemius on posterior femur
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3
Q

Describe the complications of femoral shaft fracture 1️⃣

A

Sign: tense swollen thigh

  • 1-1.5 L of blood loss I’m closed femoral shaft fractures. May develop hypovolaemic shock
  • blood loss may be double in open fractures
  • complications due to involvement of neighbouring neurovasculature within fracture site are rare
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4
Q

How are femoral shaft fractures treated? 1️⃣

A

Surgical fixation

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5
Q

What are the causes of distal femoral fractures in different patient groups? 2️⃣

A

Younger patients:
-high energy sporting injury, often significant displacement of fracture fragments

Elderly:

  • association with osteoporotic bone
  • usually mechanism is a fall from standing
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6
Q

What are the complications of distal femoral fractures? 2️⃣

A
  • popliteal artery may become involved if there is significant displacement of the fracture
  • neurovascular status of limb may be compromised so needs assessing before and after reduction of the fracture
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7
Q

What are tibial plateau fractures usually due to? 3️⃣

A

High energy injury

-usual mechanism is axial loading with varus or valgus angulation of the knee

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8
Q

What are tibial plateau fractures? 3️⃣

A

Fractures affecting the articulating surface of the tibia within the knee joint

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9
Q

What are the types of tibial plateau fractures? 3️⃣

A
  • unicondylar
  • bicondylar

Fractures affecting lateral tibial condyle are most common

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10
Q

What other damages occur with tibial plateau fractures? 3️⃣

A

-articular cartilage damage : most patients with develop a degree of post-traumatic osteoarthritis in the affected joint

  • meniscal tears
  • ACL injuries
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11
Q

What are the causes of patellar fractures? 4️⃣

A

-direct impact injury e.g.knee against dashboard
Or
-eccentric contraction of quadriceps (muscle contracting but knee joint extending)

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12
Q

Describe a blood supply finding on examination of a fractured patella 4️⃣

A
  • patella’s most important supply is via the inferior pole

- often a palpable defect in the patella and haemarthrosis

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13
Q

What happens if the extensor mechanism is disrupted? 4️⃣

A

[fracture completely splits patella distal to insertion of quadriceps tendon]
Patient will be unable to perform a straight leg raise (hip flexion whilst knee extended)

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14
Q

How are displaced and undisplaced patella fractures treated? 4️⃣

A

Displaced:
-require reduction and surgical fixation

Undisplaced:

  • do not usually require surgical fixation
  • protected whilst healing takes place through splinting and using crutches
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15
Q

What normal anatomical variant can be mistaken for a patella fracture on an X ray? 4️⃣

A

-bipartite patella
In 8% of population

-develops due to failure of union of a secondary ossification centre with the main body of the patella

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16
Q

What is a patella dislocation? 5️⃣

A

Patella being completely displaced out of its normal alignment

(Subluxation is partial displacement)

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17
Q

What is the most common direction of patellar dislocation? 5️⃣

A

-laterally

Due to Q angle between line of pull of quadriceps tendon and patellar ligament

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18
Q

How is the patella usually held in its correct position? 5️⃣

A
  • contraction of inferior fibres of vastus medialis (vastus medialis obliquus)
  • VMO stabilises patella within trochlear groove and controls patellar tracking during knee flexion and extension
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19
Q

What is the most common cause of patella dislocation? 5️⃣

A

Trauma
-often twisting injury in slight flexion
or
-a direct blow to the knee

Most commonly in athletic teenagers.
Usual mechanism is internal rotation of femur on planted foot whilst flexing knee (sudden change in direction)

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20
Q

State some factors that can predispose to patellar dislocation. 5️⃣

A
  • generalised ligament laxity
  • weakness of quadriceps tendon eps VMO
  • shallow trochlear groove with flat lateral lip
  • long patellar ligament
  • previous dislocations
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21
Q

How are patellar dislocations treated? 5️⃣

A
  • extending knee and then manually reducing the patella
  • immobilisation used whilst healing takes place
  • followed by physiotherapy to strengthen VMO
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22
Q

When do meniscal tears occur? 6️⃣

A

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

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23
Q

What are the symptoms of a meniscal tear? 6️⃣

A
  • intermittent pain localised to the joint line
  • knee clicking
  • knee catching &/or locking (inability to fully extend knee due to intra-articular foreign body)
  • sensation of giving way
  • swelling occurs as a delayed symptom due to reactive effusion or not at all as meniscal are largely avascular

A chronic effusion (increased synovial fluid) can occur due to synovitis

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24
Q

Why is acute haemarthrosis rare in cases of meniscal tears? 6️⃣

A
  • menisci largely avascular

- if present, it indicates a tear in the peripheral vascular aspect of the meniscus or associated ACL injury

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25
Q

What is found on examination of a patient with meniscal tear? 6️⃣

A
  • joint line tenderness
  • restricted motion due to pain or swelling
  • mechanical block to motion or locking can occur with a displaced tear due to loose meniscal fragments becoming trapped between the articular surfaces
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26
Q

How are meniscal tears treated? 6️⃣

A

Acute traumatic meniscal tears:
-surgically by meniscectomy or meniscal repair

Meniscal tears due to chronic degenerative process:
-similar prognosis with conservative management as with surgery hence increased use of conservative management

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27
Q

When do collateral ligament injuries occur? 7️⃣

A

Common sporting injury particularly in direct contact sports such as football

-result from acute varus or valgus angulation of the knee

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28
Q

What is the function of medial and lateral collateral ligaments? 7️⃣

A
  • normally control the lateral movement of knee joint and brace it against unusual varus or valgus deformation.
  • work with PCL to prevent excessive posterior motion of tibia on femur
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29
Q

Define varus and valgus angulation 7️⃣

A 
Varus= medial angulation of the distal segment
Valgus= lateral angulation of the distal segment
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30
Q

When are the MCL and LCL at risk? 7️⃣

A
  • MCL at risk in acute valgus strain
  • LCL at risk in varus strain

(MCL more commonly injured than LCL)

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31
Q

Why does a torn LCL have a higher chance of causing knee instability? 7️⃣

A

Medial tibial plateau forms a deeper and more stable socket for the femoral condyle than the lateral tibial plateau hence an intact LCL plays more critical role in maintaining knee stability

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32
Q

What symptoms does a patient experience following injury to collateral ligament? 7️⃣

A

Immediately after injury:

  • pain
  • swelling of knee
  • stiffness

As initial pain and stiffness subside:

  • joint may feel unstable
  • knee giving way or not supporting body weight
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33
Q

What is the Unhappy triad (‘blown knee’)? 7️⃣

A

-injury to ACL, MCL and medial meniscus

  • Results from strong force applied to lateral aspect to the knee
  • medial meniscus also injured since it is firmly adherent to the MCL
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34
Q

Which cruciate ligament is more commonly injured? 8️⃣

A

ACL and it is weaker

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35
Q

What causes the tearing of the ACL? 8️⃣

A
  • as result of a quick deceleration, hyperextension or rotational injury (following sudden change in direction)
  • non contact injury in sports
  • application of large force to back of knee with joint partly flexed
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36
Q

What are the symptoms of a torn ACL? 8️⃣

A
  • popping sensation in knee with immediate swelling
  • when swelling has subsided, experience instability of knee as tibia slides anteriorly under the femur. Knee ‘giving way’.
37
Q

Aside from preventing posterior displacement of the tibia, what other role does the ACL have? 8️⃣

A

Controls the rotational stability of the knee by preventing medial rotation of the tibia when knee is extended

38
Q

Describe anterolateral rotatory instability in cases of torn ACL 8️⃣

A
  • rotation of tibia occurs with PCL as the centrally located axis
  • medial tibial condyle rotates internally
  • lateral tibial condyle subluxes anteriorly
  • spontaneous reduction of the lateral tibial condyle occurs with a sudden ‘slip’ when knee if flexed to 20-40degrees
  • characterised by sudden sensation of knee ‘giving way’
39
Q

How is a ruptured ACL treated? 8️⃣

A
  • some patients, particularly those with low functional demands can function well with ruptured ACL, using musculature to stabilise joint
  • sportsman and very active people will often need surgical reconstruction
40
Q

What is the most common mechanism of PCL injury? 8️⃣

A
  • ‘dashboard injury’
  • knee flexed and a large force applied to upper tibia, displacing it posteriorly
  • seen in road traffic collisions when proximal tibia collides with dashboard
41
Q

What are some other causes of PCL injury? 8️⃣

A
  • torn during sports such as football
  • tibia hits ground first and displaced posteriorly, avulsing PCL
  • tackle with the knee flexed can also cause this injury

-severe hyperextension injury can caused avulsion of PCL from its insertion on the posterior aspect of the intercondylar area

42
Q

What happens after a PCL injury? 8️⃣

A

-tibia can be displaced posteriorly on the femur

43
Q

How is a PCL injury treated? 8️⃣

A

-conservative management

With bracing and rehabilitation

44
Q

How can ACL and PCL injuries be detected? 8️⃣

A

ACL

  • anterior drawer test
  • Lachman’s test

PCL
-posterior drawer test

45
Q

What causes dislocation of the knee joint? 9️⃣

A
  • its an uncommon injury

- always results from a high energy trauma

46
Q

To dislocate the knee, which ligaments must be ruptured? 9️⃣

A

At least 3 out of 4 ligaments:

-MCL, LCL, ACL or PCL

47
Q

Why is it common for an associated arterial injury to occur with a dislocated knee joint? 9️⃣

A
  • popliteal artery is tethered proximally when it enters then popliteal fossa at the adductor hiatus and distally where it exits the popliteal fossa by passing under the tendinous arch of the soleus muscle.
  • popliteal artery is so immobile
48
Q

What can an injury of the popliteal artery result in? 9️⃣

A

May tear
-resulting in an obvious haematoma

May be crushed or suffer a traction injury
-with endothelial damage leading to subsequent thrombotic occlusion

49
Q

What clinical assessment is essential following reduction of the knee joint? 9️⃣

A

Assess the vascularity of the leg

E.g. with magnetic resonance angiography

50
Q

What can swellings around the knee be? 1️⃣0️⃣

A

-bony e.g. Osgood-Schlatter’s disease
-soft tissue
>localised e.g. enlarged popliteal lymph node or poplitealartery aneurysm
>generalised e.g. lymphoedema of the lower limb
-fluid
>inside the joint = effusion
>outside the joint = soft tissue haematoma

51
Q

What is a knee effusion? 1️⃣1️⃣

A

Accumulation of the fluid inside the knee joint

52
Q

How does an acute effusion differ from a delayed effusion? 1️⃣1️⃣

A

Acute
- <6hrs after injury e.g. after cruciate ligament rupture

Delayed
- >6hrs after injury

53
Q

What is delayed swelling of the knee usually due to? 1️⃣1️⃣

A

-reactive synovitis in response to injury, leading to production of increased volume of synovial fluid

54
Q

What can acute knee effusions be divided into? 1️⃣1️⃣

A

-haemarthrosis (blood in joint)
Diagnostically, a haemarthrosis is an ACL rupture until proven otherwise

-lipo-haemarthrosis (blood & fat in joint)
Diagnostically, it is a fracture until proven otherwise as fat has usually been released from the bone marrow

55
Q

What can be seen on an x-ray in cases of lipo-haemarthrosis? 1️⃣1️⃣

A

Fat-fluid interface

-fat is less dense than blood so absorbs fewer x-rays and therefore appears darker than blood.

56
Q

What is bursitis? 1️⃣2️⃣

A

It is the inflammation of a bursa

57
Q

Which bursa of the knee are most commonly inflamed? 1️⃣2️⃣

A
  • prepatellar bursa
  • infrapatellar bursa
  • pes anserinus bursa
  • suprapatellar bursa
58
Q

What is the pre-patellar bursa? 1️⃣3️⃣

A

Superficial bursa with a thin synovial lining, located between the skin and the patella

Does not communicate with joint space and usually contains a minimal amount of fluid

59
Q

How does a patient with pre-patellar bursitis usually present? 1️⃣3️⃣

A
  • knee pain
  • swelling
  • some erythema overlying the inflamed bursa
  • difficult to walk due to pain
  • not able to kneel on affected side
60
Q

What can cause pre-patellar bursitis? 1️⃣3️⃣

A

-repetitive trauma to the bursa

E.g. may occur during scrubbing the floor, hence ‘Housemaid’s knees’ as they tend to lean forwards whilst scrubbing

-occasionally may be a history of a fall into the knee or a blunt trauma to the knee

61
Q

What does the infrapatellar bursa essentially consist of? 1️⃣4️⃣

A

2 bursa

  • one sitting superficially between patellar ligament and skin
  • other is the deep infrapatellar bursa which is between the patella ligament and tibia bone

*bursitis more commonly affects the superficial infrapatellar bursa

62
Q

What can cause infrapatellar bursitis? 1️⃣4️⃣

A

-repeated microtrauma caused by activities involving kneeling

‘Clergyman’s knees’ reflects more upright position of kneeling that generally triggers this condition

63
Q

What is the suprapatellar bursa? 1️⃣5️⃣

A

It is an extension of the synovial cavity of the knee joint

64
Q

How does a knee effusion present? 1️⃣5️⃣

A

With swelling in the suprapatellar pouch

Hence rather than being a sign of localised irritation, ‘suprapatellar bursitis’ is usually a sign of significant pathology in the knee joint

65
Q

What are the causes of a knee effusion? 1️⃣5️⃣

A
  • osteoarthritis
  • RA
  • infection (septic arthritis)
  • gout and psuedogout
  • repetitive microtrauma to the joint
66
Q

Where is the semimembranosus bursa located? 1️⃣6️⃣

A
  • beneath deep fascia of the popliteal fossa in the interval between the semimembranosus and medial head of the grastrocnemius
  • attached to posterior capsule of the knee joint and may communicate with it via a small opening
67
Q

What is semimembranosus bursitis an indirect consequence of? 1️⃣6️⃣

A
  • swelling within knee joint
  • if knee joint inflamed and there is an effusion, the fluid can force its way through the narrow communication into the semimembranosus
  • the resulting swelling in the popliteal fossa is known as semimembranosus bursitis or popliteal cyst or Baker’s cyst
68
Q

What is Osgood-Schlatter’s disease (OSD) ? 1️⃣7️⃣

A

Inflammation of the apophysis (site of insertion) of the patellar ligament into the tibial tuberosity

69
Q

Who does OSD most commonly occur in? 1️⃣7️⃣

A

In teenagers who play sport (running and jumping)

70
Q

What are the symptoms of OSD? 1️⃣7️⃣

A
  • localised pain and swelling
  • intense knee pain during running, jumping, squatting, kneeling, ascending and descending stairs

(Bilateral in 20-30% of cases)

71
Q

How is OSD treated? 1️⃣7️⃣

A
  • usually resolves with rest and ice
  • pain and swelling resolve at the age of skeletal maturity when the apophysis (which has a separate ossification centre) fuses

-bony prominence usually remains permanent

72
Q

What are the typical symptoms of knee osteoarthritis? 1️⃣8️⃣

A
  • knee pain
  • stiffness
  • swelling
73
Q

Give examples of pain following a pattern in knee OA 1️⃣8️⃣

A
  • knee pain that comes and goes, possibly with chronic low level of pain punctuated by more severe flare ups
  • pain precipitated by activities such as bending, kneeling, squatting or climbing stairs
  • pain and stiffness that is worse after prolonged inactivity or rest such as getting out of bed in the morning
74
Q

What deformities are common at the knee joint with OA? 1️⃣8️⃣

A
  • varus deformity
  • valgus deformity
  • fixed flexion deformity -knee can’t be fully extended
75
Q

What can OA of the knee also result in? 1️⃣8️⃣

A
  • increased friction as bone rubs on bone, felt as crepitus
  • effusion may develop and swelling further limits joint movement
  • muscle weakness esp of quadriceps, leasing to joint instability, felt as knee giving way or buckling esp when walking down stairs
76
Q

How can osteoarthritis be compartmental? 1️⃣8️⃣

A

Uni-, bi- or tri- compartmental

affecting 1,2 or 3 of the

  • medial femorotibial compartment
  • lateral femorotibial compartment
  • patellofemoral compartment
77
Q

What are the risk factors for knee osteoarthritis? 1️⃣8️⃣

A
  • age
  • female sex
  • previous trauma to joint
  • obesity
  • family history of OA
  • having another condition affecting the joint e.g RA, gout, septic arthritis, haemophilia with haemarthrosis
78
Q

How is knee OA treated? 1️⃣8️⃣

A

initially,

  • strengthening exercises to strengthen VMO and reduce instability
  • analgesia
  • weight loss if overweight
  • activity modification

Ultimately, many patients will require surgery in the form of a Total knee replacement (TKR)

79
Q

What is septic arthritis? 1️⃣9️⃣

A

The invasion of the joint space by microorganisms, usually bacteria.

Differs from reactive arthritis which is a sterile inflammatory process that can result from an extra-articular infection

80
Q

What joints does septic arthritis affect? 1️⃣9️⃣

A

-most commonly knee joint

  • hip
  • shoulder
  • ankle
  • wrists
81
Q

What pathogens cause septic arthritis? 1️⃣9️⃣

A
  • most commonly staph. aureus
  • staph. Epidermis
  • Neisseria gonorrhoea
  • strep. Viridans
  • strep. pneumonia
  • group B streptococci
82
Q

What are the risk factors for septic arthritis? 1️⃣9️⃣

A
  • extremes of age
  • diabetes mellitus
  • RA
  • immunosuppression
  • IV drug use
83
Q

Why are prosthetic joints particularly at risk of septic arthritis? 1️⃣9️⃣

A

-intraopererative contamination
or
-haematogenous spread from an distant infective focus

-patient may become symptomatic months or even years after initial operation

  • delayed wound healing is a major risk factor for prosthetic joint infections
  • biofilm produced by staph epidermis protects the pathogen from the host defences and from antibiotics
  • polymethacrylate cement used in the joint replacement also inhibits white blood cell and complement function, thereby increasing risk of infection
84
Q

What is the major consequence of bacterial invasion in septic arthritis? 1️⃣9️⃣

A
  • damage time articular cartilage either due to organism’s pathological properties or to the host immune response
  • neutrophils stimulate synthesis of cytokines and other inflammatory products, resulting in the hydrolysis of collagen and proteoglycans
85
Q

How do patients with septic arthritis present? 1️⃣9️⃣

A

Symptom triad

  • fever, usually low grade (with rigors present in 20% of cases)
  • pain
  • reduced range of motion

Symptoms may evolve over a few days to a few weeks

86
Q

What should the joint be examined for? 1️⃣9️⃣

A
  • erythema
  • swelling, 90% have an obvious effusion
  • warmth
  • tenderness
  • limitation of active and passive range of motion
  • physical finding are usually minimal in infection of a prosthetic joint and swelling is only slight.
  • The most distinctive finding is a draining sinus (tract between site of infection and surface of overlying skin) which originates from the underlying infected joint
87
Q

If septic arthritis is suspected, what should be done? 1️⃣9️⃣

A
  • carry out joint aspiration immediately

- send aspirate for urgent microscopy, culture and sensitivities

88
Q

How can patients with treated septic arthritis be affected? 1️⃣9️⃣

A

-50% adults will have decreased range of motion or chronic pain after infection had resolved

MSK Clinical Conditions (9 decks)

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