15. Disorder Of The Knee Flashcards
1
Q
What is reduction?
A
Procedure to repair a fracture or dislocation to the correct alignment (can be open or closed reduction)
2
Q
Procedure to repair a fracture or dislocation to the correct alignment (can be open or closed reduction)
A
AP (anteroposterior) view, lateral view and a patella axial (‘skyline’) view
3
Q
What is the common cause of femoral shaft fractures in healthy children and young adults?
A
High velocity trauma e.g. road traffic collision, falls from a height
4
Q
When might a low velocity injury cause a femoral shaft fracture?
A
In the elderly with osteoporotic bones, or in patients with bone metastases or other bone lesions (e.g. bone cysts
5
Q
How much blood might be lost in a closed femoral fracture and what might this lead to?
A
1-1.5L - may develop hypovolaemic shock
- blood loss in open femoral fracture may be double this amount
6
Q
In a femoral shaft fracture, how does the leg present?
A
The proximal fragment is often abducted due to the pull of gluteus medius and minimus on the greater trochanter and flexed due to the action of iliopsoas on the lesser trochanter.
The distal segment is adducted into a varus deformity due to the action of the adductor muscles (adductor magnus, gracilis) and extended due to the pull of gastrocnemius on the posterior femur.
7
Q
How are femoral shaft fractures treated?
A
treated with surgical fixation.
8
Q
What normally causes distal femoral fractures in the young and old?
A
Young: high-energy sporting injury - often significant displacement of the fracture fragments
Old: fall from standing - usually seen in association with osteoporotic bone
9
Q
Which artery may become involved if there is significant displacement of the fracture in a distal femoral fracture?
A
Popliteal artery
10
Q
What are tibial plateau fractures?
A
Fractures affecting the articulating surface of the tibia within the knee joint. They can be unicondylar (affecting one condyle) or bicondylar
11
Q
What condyle is most commonly affected in tibial plateau fractures?
A
Lateral tibial condyle
12
Q
What is the usual fracture line in tibial plateau fractures?
A
Axial (top to bottom)
- with varus or valgus angulation (an abnormal medial or lateral flexion load) of the knee
- high-energy injuries
13
Q
What will patients develop a degree of after treatment for tibial plateau fracture?
A
Most patients will develop a degree of post-traumatic osteoarthritis in the affected joint
14
Q
What are tibial plateau fractures associated with?
A
Meniscal tears and anterior cruciate ligament injury
15
Q
What 2 things can cause patellar fractures?
A
- direct impact injury
- eccentric contraction of the quadriceps (the muscle is contracting but the joint is extending)
16
Q
What is seen on examination of a fractured patella?
A
Palpable defect in the patella and a haemarthrosis (blood in the joint)
17
Q
How might a patella fracture disrupt the extensor muscles?
A
Fracture may completely split the patella distal to the insertion of the quadriceps tendon.
18
Q
How can extensor disruption be tested for in a patella fracture?
A
Patient would be unable to do a straight leg raise (i.e. flexed thigh at hip, extended leg at the knee)
19
Q
What may be mistaken for a patella fracture?
A
A bipartite patella (patella in 2 parts)
- occurs in 8% of population
20
Q
Why does bipartite patella occur?
A
Because there is failure of union of a secondary ossification centre with the main body of the patella
- It is a normal anatomical variant.
21
Q
What is the treatment for displaced patella fractures?
A
Reduction and surgical fixation
22
Q
What is the treatment for undisplaced patella fractures?
A
- Do not usually require surgical fixation
- protected whilst healing takes place through splinting and using crutches
23
Q
What does patella dislocation refer to?
A
Patella being completely displaced out of its normal alignment
24
Q
What is a subluxation?
A
Partial dislocation
25
What is the most common direction for the patella to dislocate?
due to the ‘Q angle’ between the line of pull of the quadriceps tendon and the patellar ligament, the most
common direction for the patella to dislocate is laterally.
The patella is usually held in the correct position by contraction of the inferior, almost horizontal, fibres of vastus medialis, the vastus medialis obliquus (VMO).
The specific role of the VMO is to stabilise the patella within the trochlear groove and to control tracking of the patella when the knee is flexed and extended
26
What are some factors that can predispose to patellar dislocation?
- Generalised ligamentous laxity
- Weakness of the quadriceps muscles, especially the VMO
- Shallow trochlear (patellofemoral) groove with a flat lateral lip
- Long patellar ligament
- Previous dislocations
27
What are the common causes of patella dislocation?
Most common cause is trauma, often a twisting injury in slight flexion or a direct blow to the knee
Common in sports: internal rotation of the femur on a planted foot whilst flexing the knee (e.g. in a sudden change of direction during sports)
28
What does treatment of patella dislocation involve?
- extending the knee
- manually reducing the patella.
- immobilisation is used whilst healing takes place
- followed by physiotherapy to strengthen VMO
29
In what movement do meniscal injuries/tears usually occur?
During a sudden twisting motion of a weight-bearing knee in a high degree of flexion
30
What might a patient with meniscal injury describe?
Intermittent pain, localised to the joint line, alongside reports of the knee clicking, catching, locking or a sensation of giving way
31
Why might there be mechanical block to motion or locking in a meniscal injury?
Due to loose meniscal fragments becoming trapped between the articular surfaces (intra articular foreign bodies)
32
When might swelling occur in a meniscal injury?
- delayed symptom due a reactive effusion
| - or not at all, as the menisci are largely avascular (except at their periphery) (haemarthrosis is therefore rare)
33
What does haemarthrosis in a meniscal injury indicate?
Indicates a tear in the peripheral vascular aspect of the meniscus or an associated injury to the anterior cruciate ligament
34
Why might lead to increased synovial fluid in a mensical tear?
A chronic effusion (increased synovial fluid) can occur due to synovitis (inflammation of the synovial membrane)
35
How are Acute traumatic meniscal tears treated?
Surgically by either meniscectomy or meniscal repair
36
How are chronic traumatic meniscal tears treated?
Similar prognosis with conservative management as with surgery. Hence, conservative management is increasingly being recommended
37
What do collateral ligament injuries usually result from?
acute varus or valgus angulation of the knee
38
Which collateral ligament is injured more commonly and damage to which has higher chance of causing knee instability?
MCL is injured more commonly than the LCL, but a torn LCL has a higher change of causing knee instability
39
Why does a torn LCL have a higher chance on causing knee instability than torn MCL?
Medial tibial plateau forms a deeper and more stable socket for the femoral condyle than the lateral tibial plateau. Hence, an intact LCL plays a more critical role in maintaining the stability of the knee
40
What is varus and valgus?
```
Varus = medial angulation of the distal segment
Valgus = lateral angulation of the distal segment (Remember vaLgus = Lateral)
```
41
What is the function of the medial and lateral collateral ligaments?
The medial and lateral collateral ligaments normally control the lateral movement of the knee joint and brace it against unusual varus or valgus deformation. Together, the collateral ligaments also work with the posterior cruciate ligament (PCL) to prevent excessive posterior motion of the tibia on the femur.
42
Which of the ligaments is at risk in varus strain and valgus strain?
In acute valgus strain, the medial collateral ligament (MCL) is at risk
in varus strain the lateral collateral ligament (LCL) is at risk.
43
What will the patient complain of in a collateral ligament injury?
- immediate: pain and swelling
| - then: instability, giving way, not supporting their body weight
44
What is the unhappy triad?
Injury to the anterior cruciate ligament, medial collateral ligament and medial meniscus
45
What type of force causes the unhappy triad?
Valgus (lateral) force - a strong force applied to the lateral aspect of the knee
46
In an unhappy triad, why is the medial meniscus also injured?
The medial meniscus is firmly adherent to the medial collateral ligament, which is why it is also injured
47
Which cruciate ligament is more commonly injured?
Anterior - it is weaker
48
What causes a tear in the anterior cruciate ligament?
Quick deceleration, hyperextension, rotational injury or large force to the back of the knee with the joint partly flexed
49
What will the patient complain of in an anterior cruciate ligament injury?
- popping sensation in their knee with immediate swelling
- . When the swelling has subsided, instability of the knee as the tibia slides anteriorly under the femur. Patients tend to describe this as the knee ‘giving way’.
50
In which direction might the tibia move in an anterior cruciate ligament tear?
Anteriorly under the femur
- may also rotate medially as the ACL plays a role in controlling the rotational stability of the knee by preventing medial (internal) rotation of the tibia when the knee is extended. If the ACL is torn, rotation of the tibia occurs with the PCL as the centrally-located axis;
the medial tibial condyle rotates internally and the lateral tibial condyle subluxes anteriorlylly. Spontaneous reduction of the lateral tibial condyle then occurs with a sudden ‘slip’ when the knee is flexed to 20-40˚. This is characterized by a sudden sensation of the knee ‘giving way’ and is called anterolateral rotatory instability.
51
What treatment is used for ACL injury?
Surgical reconstruction
| - may not be required in patients with low functional demands on their knees
52
What mechanisms can cause posterior collateral ligament injury?
'dashboard injury'; the knee is flexed and a large force is applied to the upper tibia, displacing it posteriorly
Player falls on a flexed knee with their ankle plantarflexed. The tibia hits the ground first and is displaced posteriorly, avulsing the PCL
Severe hyperextension injury can also avulse the PCL from its insertion on the posterior aspect of the intercondylar area
53
After a PCL tear, what type of displacement can occur?
Tibia posteriorly displaced on the femur
54
What type of treatment is used for PCL tears?
Respond well to conservative management with bracing and rehabilitation
55
What test can be used to detect anterior and posterior cruciate ligament injuries?
Anterior and posterior drawer tests (respectively)
Lachman's test can also be used to detect ACL injuries
56
How many ligaments must be ruptured to dislocate a knee joint?
3 or 4 (ACL, PCL, LCL, MCL)
57
What is associated with knee joint dislocation?
Arterial damage
58
Why is an associated arterial injury very common with knee joint dislocation?
popliteal artery is immobile: tethered proximally when it enters the popliteal fossa at the adductor hiatus and distally where it exits the popliteal fossa by passing under the tendinous arch of the soleus muscle
59
How may the popliteal artery be affected in a knee joint dislocation
- tear resulting in an obvious haematoma
- or it may be crushed
- or suffer a traction injury
60
What is the treatment for knee joint dislocation
- reduction
| - vascularity assessment with MRA (magnetic resonance angiography)
61
What can swellings around a knee be?
Bony e.g. Osgood-Schlatter's disease
Soft tissue
- Localised e.g. an enlarged popliteal lymph node; a popliteal artery aneurysm
- Generalised e.g. lymphoedema of the lower limb
Fluid
- Inside the joint = effusion
- Outside the joint = soft tissue haematoma
62
What is an effusion and what are the 2 classification?
Accumulation of fluid inside the knee joint; it is never normal
- acute or delayed
63
How is an acute effusion defined?
< 6 hours after injury
64
How is a delayed effusion defined?
> 6 hours after injury
65
What usually causes delayed effusion?
Usually due to reactive synovitis. Inflammation of the synovium, in response to injury, leads to the
production of an increased volume of synovial fluid
66
What are 2 divisions of acute knee effusions?
- Haemarthrosis (blood in the joint)
| - Lipo-haemarthrosis (blood and fat in the joint)
67
What is the diagnosis of haemarthrosis of knee unless proven otherwise?
ACL rupture
68
What is the diagnosis of lipo-haemarthrosis unless proven otherwise and why?
Fracture until proven otherwise
| - as the fat has usually released from the bone marrow in fractures
69
In a lipo-haemarthrosis, what is usually seen on an x-ray?
a fat-fluid interface can be seen on the X-ray. Fat is less dense than blood, absorbs fewer X-rays and therefore appears darker than blood on the X-ray film.
70
Which bursae are most commonly inflammed?
Prepatellar bursa, infrapatellar bursa, pes anserinus (subsartorial) bursa, suprapatellar bursa
71
What might a patient with pre-patellar bursitis present with?
- knee pain and swelling
- erythema overlying the inflamed bursa
- difficult to walk due to the pain
- will not be able to kneel on the affected side
72
What is bursitis?
Bursitis is inflammation of a bursa
73
What could lead to pre-patellar bursitis?
- history of repetitive trauma to the bursa
| - history of fall onto the knee or blunt trauma to the knee (symptoms presentation 10 days after the incident)
74
What is pre-patella bursitis also called?
Housmaids knee: housemaids tend to learn forwards on their knees whilst scrubbing, it is the pre-patellar bursa that tends to become inflamed
75
Where is the pre-patellar bursa located and what happens when there is inflammation?
The pre-patellar bursa is a superficial bursa with a thin synovial lining, located between the skin and the patella.
It is does not communicate with the joint space and usually contains a minimal amount of fluid. Inflammation of this bursa, however, results in a marked increase of fluid within the space.
76
Which infra-patellar bursa does bursitis most usually affect?
superficial infrapatellar bursa.
77
What are the two infrapatellar bursae?
one of which sits superficially between the patella tendon (below the kneecap) and the skin and
the second referred to as the deep infrapatellar bursa is sandwiched between the patella tendon and tibia bone (shin).
78
What causes infra-patellar bursitis?
Repeated microtrauma caused by activities involving kneeling
| - kneeling in upright position
79
What is infra-patellar bursitis also called?
Clergyman's knee
80
What is supra-patellar bursitis an indication of and why?
Sign of significant pathology in the knee joint
- is an extension of the synovial cavity of the knee joint
- A knee effusion therefore often presents with swelling in the suprapatellar pouch
81
Where is the supra-patellar bursa located?
the suprapatellar bursa extends superiorly from beneath the patella under the quadriceps muscle
82
What causes suprapatellar bursitis?
Knee effusion
| - it is an extension of the synovial cavity of the knee
83
What are some causes of knee effusion?
- Osteoarthritis
- Rheumatoid arthritis
- Infection (septic arthritis)
- Gout and pseudogout
- Repetitive microtrauma to the joint (as a result of running on soft or uneven surfaces).
84
What can cause semimembranosus bursitis and why?
Indirect consequence of swelling within the knee joint
- attached to the posterior capsule of the knee joint and may communicate with it by a small opening. If the knee joint is inflamed and there is an effusion, the fluid can force its way through this narrow communication into the semimembranosus bursa
85
Where is the semimembranosus bursa located?
located beneath the deep fascia of the popliteal fossa in the interval between the semimembranosus muscle and the medial head of the gastrocnemius muscle
86
Where in the limb does swelling in semimembranosus bursa show and what is it also called?
Popliteal fossa
| - called popliteal cyst or Baker's cyst
87
What is Osgood-Schlatter's disease (OSD)?
Inflammation of the apophysis (site of insertion) of the patellar ligament into the tibial tuberosity
88
What might a patient with OSD present with?
- localised pain and swelling
| - intense knee pain during running, jumping, squatting, ascending and descending stairs and during kneeling
89
How is OSD treated?
Usually resolves with rest and ice
90
Who are OSD most common in?
teenagers who play sport (running and jumping)
91
When does pain and swelling accompanying OSD resolve?
When does pain and swelling accompanying OSD resolve?
92
What are the typical symptoms of knee osteoarthritis
knee pain, stiffness and swelling
93
Which patterns may osteoarthritic knee pain follow?
Knee pain that comes and goes, possibly with a 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.
94
How does osteoarthritis present?
patient may develop a varus deformity (deviation of the distal component toward the midline), a valgus deformity (deviation away from the midline) or a fixed flexion deformity (in which the knee cannot be fully extended)
95
Define the term crepitus in terms of the knee joint and explain why is occurs
A grating sound and crackling sensation on movement of the joint
Caused by friction of the knee joint
96
What may develop with osteoarthritis of the knee which causes further swelling?
An effusion may develop and the swelling further limits joint movement.
97
Why may Some patients with knee OA feel their knee giving way or buckling?
This is likely to be due to muscle weakness, especially
| of the quadriceps muscles, leading to instability of the joint.
98
Risk factors for OA
Age, female gender, previous trauma to joint, obesity, family history, joint affecting diseases.
99
What are the treatments for OA of the knee?
- strengthening exercises to strengthen the vastus medialis muscle and therefore reduce instability.
- Analgesia,
- weight loss
- activity modification
- surgery in the form of a total knee replacement (TKR)
100
What is septic arthritis?
the invasion of the joint space by micro-organisms, usually bacteria (but occasionally viruses, mycobacteria and fungi)
- It differs from reactive arthritis, which is a sterile inflammatory process that can result from an extra-articular infection e.g. gastroenteritis
101
What is the common pathogen for septic arthritis?
The most common pathogen is Staphylococcus aureus.
Other pathogens include Staph. epidermidis, Neisseria gonorrhoeae (in sexually active individuals), Strep. viridans, Strep. pneumoniae and the Group B Streptococci.
102
What are the risk factors for septic arthritis?
extremes of age, diabetes mellitus, rheumatoid arthritis, immunosuppression and intravenous drug abuse
103
Which joints are particularly at risk of septic arthrits?
Prosthetic joints
- either due to intraoperative contamination or to haematogenous spread from a distant infective focus. -- Delayed wound healing is a major risk factor for prosthetic joint infection. The biofilm produced
by Staph. epidermidis protects this pathogen from the host's defences and from antibiotics
- Polymethacrylate cement used in the joint replacement also inhibits white blood cell and complement function, thereby increasing the risk of infection.
104
What is the consequence of invasion of the joint space by micro-organisms in septic arthrtis?
The major consequence of bacterial invasion is damage to articular cartilage, either due to the organism's pathologic properties (e.g. proteases secreted by Staph. aureus) or to the host's immune response. Neutrophils stimulate synthesis of cytokines and other inflammatory products, resulting in the hydrolysis of collagen and proteoglycans
105
What are the symptom triad of septic arthritis?
Fever (40-60% of cases) - usually low grade with rigors present in only 20% of cases.
Pain (75%)
Reduced range of motion.
106
How is a patient examined for septic arthritis?
The joint should be examined for erythema, swelling (90% have an obvious effusion), warmth, tenderness, and limitation of active and passive range of motion.
Conversely, the physical findings are usually minimal in infection of a prosthetic joint, and swelling is only slight. The most distinctive finding is a draining sinus
(tract between the site of infection and surface of the overlying skin), which originates from the underlying infected joint.
107
What is performed if septic arthritis is suspected?
aspiration of the joint should be carried out immediately and the aspirate should be sent for urgent microscopy, culture and sensitivities
