Conditions Of The Knee Flashcards
What are the possible causes of femoral shaft fractures in different patient groups? 1️⃣
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
How does the musculature act as a deforming force after a femoral shaft fracture? 1️⃣
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
Describe the complications of femoral shaft fracture 1️⃣
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
How are femoral shaft fractures treated? 1️⃣
Surgical fixation
What are the causes of distal femoral fractures in different patient groups? 2️⃣
Younger patients:
-high energy sporting injury, often significant displacement of fracture fragments
Elderly:
- association with osteoporotic bone
- usually mechanism is a fall from standing
What are the complications of distal femoral fractures? 2️⃣
- 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
What are tibial plateau fractures usually due to? 3️⃣
High energy injury
-usual mechanism is axial loading with varus or valgus angulation of the knee
What are tibial plateau fractures? 3️⃣
Fractures affecting the articulating surface of the tibia within the knee joint
What are the types of tibial plateau fractures? 3️⃣
- unicondylar
- bicondylar
Fractures affecting lateral tibial condyle are most common
What other damages occur with tibial plateau fractures? 3️⃣
-articular cartilage damage : most patients with develop a degree of post-traumatic osteoarthritis in the affected joint
- meniscal tears
- ACL injuries
What are the causes of patellar fractures? 4️⃣
-direct impact injury e.g.knee against dashboard
Or
-eccentric contraction of quadriceps (muscle contracting but knee joint extending)
Describe a blood supply finding on examination of a fractured patella 4️⃣
- patella’s most important supply is via the inferior pole
- often a palpable defect in the patella and haemarthrosis
What happens if the extensor mechanism is disrupted? 4️⃣
[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)
How are displaced and undisplaced patella fractures treated? 4️⃣
Displaced:
-require reduction and surgical fixation
Undisplaced:
- do not usually require surgical fixation
- protected whilst healing takes place through splinting and using crutches
What normal anatomical variant can be mistaken for a patella fracture on an X ray? 4️⃣
-bipartite patella
In 8% of population
-develops due to failure of union of a secondary ossification centre with the main body of the patella
What is a patella dislocation? 5️⃣
Patella being completely displaced out of its normal alignment
(Subluxation is partial displacement)
What is the most common direction of patellar dislocation? 5️⃣
-laterally
Due to Q angle between line of pull of quadriceps tendon and patellar ligament
How is the patella usually held in its correct position? 5️⃣
- 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
What is the most common cause of patella dislocation? 5️⃣
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)
State some factors that can predispose to patellar dislocation. 5️⃣
- generalised ligament laxity
- weakness of quadriceps tendon eps VMO
- shallow trochlear groove with flat lateral lip
- long patellar ligament
- previous dislocations
How are patellar dislocations treated? 5️⃣
- extending knee and then manually reducing the patella
- immobilisation used whilst healing takes place
- followed by physiotherapy to strengthen VMO
When do meniscal tears occur? 6️⃣
Occur during a sudden twisting motion of a weight bearing knee in a high degree of flexion
What are the symptoms of a meniscal tear? 6️⃣
- 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
Why is acute haemarthrosis rare in cases of meniscal tears? 6️⃣
- menisci largely avascular
- if present, it indicates a tear in the peripheral vascular aspect of the meniscus or associated ACL injury
What is found on examination of a patient with meniscal tear? 6️⃣
- 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
How are meniscal tears treated? 6️⃣
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
When do collateral ligament injuries occur? 7️⃣
Common sporting injury particularly in direct contact sports such as football
-result from acute varus or valgus angulation of the knee
What is the function of medial and lateral collateral ligaments? 7️⃣
- 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
Define varus and valgus angulation 7️⃣
Varus= medial angulation of the distal segment Valgus= lateral angulation of the distal segment
When are the MCL and LCL at risk? 7️⃣
- MCL at risk in acute valgus strain
- LCL at risk in varus strain
(MCL more commonly injured than LCL)
Why does a torn LCL have a higher chance of causing knee instability? 7️⃣
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
What symptoms does a patient experience following injury to collateral ligament? 7️⃣
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
What is the Unhappy triad (‘blown knee’)? 7️⃣
-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
Which cruciate ligament is more commonly injured? 8️⃣
ACL and it is weaker
What causes the tearing of the ACL? 8️⃣
- 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
What are the symptoms of a torn ACL? 8️⃣
- 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’.
Aside from preventing posterior displacement of the tibia, what other role does the ACL have? 8️⃣
Controls the rotational stability of the knee by preventing medial rotation of the tibia when knee is extended
Describe anterolateral rotatory instability in cases of torn ACL 8️⃣
- 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’
How is a ruptured ACL treated? 8️⃣
- 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
What is the most common mechanism of PCL injury? 8️⃣
- ‘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
What are some other causes of PCL injury? 8️⃣
- 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
What happens after a PCL injury? 8️⃣
-tibia can be displaced posteriorly on the femur
How is a PCL injury treated? 8️⃣
-conservative management
With bracing and rehabilitation
How can ACL and PCL injuries be detected? 8️⃣
ACL
- anterior drawer test
- Lachman’s test
PCL
-posterior drawer test
What causes dislocation of the knee joint? 9️⃣
- its an uncommon injury
- always results from a high energy trauma
To dislocate the knee, which ligaments must be ruptured? 9️⃣
At least 3 out of 4 ligaments:
-MCL, LCL, ACL or PCL
Why is it common for an associated arterial injury to occur with a dislocated knee joint? 9️⃣
- 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
What can an injury of the popliteal artery result in? 9️⃣
May tear
-resulting in an obvious haematoma
May be crushed or suffer a traction injury
-with endothelial damage leading to subsequent thrombotic occlusion
What clinical assessment is essential following reduction of the knee joint? 9️⃣
Assess the vascularity of the leg
E.g. with magnetic resonance angiography
What can swellings around the knee be? 1️⃣0️⃣
-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
What is a knee effusion? 1️⃣1️⃣
Accumulation of the fluid inside the knee joint
How does an acute effusion differ from a delayed effusion? 1️⃣1️⃣
Acute
- <6hrs after injury e.g. after cruciate ligament rupture
Delayed
- >6hrs after injury
What is delayed swelling of the knee usually due to? 1️⃣1️⃣
-reactive synovitis in response to injury, leading to production of increased volume of synovial fluid
What can acute knee effusions be divided into? 1️⃣1️⃣
-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
What can be seen on an x-ray in cases of lipo-haemarthrosis? 1️⃣1️⃣
Fat-fluid interface
-fat is less dense than blood so absorbs fewer x-rays and therefore appears darker than blood.
What is bursitis? 1️⃣2️⃣
It is the inflammation of a bursa
Which bursa of the knee are most commonly inflamed? 1️⃣2️⃣
- prepatellar bursa
- infrapatellar bursa
- pes anserinus bursa
- suprapatellar bursa
What is the pre-patellar bursa? 1️⃣3️⃣
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
How does a patient with pre-patellar bursitis usually present? 1️⃣3️⃣
- knee pain
- swelling
- some erythema overlying the inflamed bursa
- difficult to walk due to pain
- not able to kneel on affected side
What can cause pre-patellar bursitis? 1️⃣3️⃣
-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
What does the infrapatellar bursa essentially consist of? 1️⃣4️⃣
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
What can cause infrapatellar bursitis? 1️⃣4️⃣
-repeated microtrauma caused by activities involving kneeling
‘Clergyman’s knees’ reflects more upright position of kneeling that generally triggers this condition
What is the suprapatellar bursa? 1️⃣5️⃣
It is an extension of the synovial cavity of the knee joint
How does a knee effusion present? 1️⃣5️⃣
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
What are the causes of a knee effusion? 1️⃣5️⃣
- osteoarthritis
- RA
- infection (septic arthritis)
- gout and psuedogout
- repetitive microtrauma to the joint
Where is the semimembranosus bursa located? 1️⃣6️⃣
- 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
What is semimembranosus bursitis an indirect consequence of? 1️⃣6️⃣
- 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
What is Osgood-Schlatter’s disease (OSD) ? 1️⃣7️⃣
Inflammation of the apophysis (site of insertion) of the patellar ligament into the tibial tuberosity
Who does OSD most commonly occur in? 1️⃣7️⃣
In teenagers who play sport (running and jumping)
What are the symptoms of OSD? 1️⃣7️⃣
- localised pain and swelling
- intense knee pain during running, jumping, squatting, kneeling, ascending and descending stairs
(Bilateral in 20-30% of cases)
How is OSD treated? 1️⃣7️⃣
- 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
What are the typical symptoms of knee osteoarthritis? 1️⃣8️⃣
- knee pain
- stiffness
- swelling
Give examples of pain following a pattern in knee OA 1️⃣8️⃣
- 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
What deformities are common at the knee joint with OA? 1️⃣8️⃣
- varus deformity
- valgus deformity
- fixed flexion deformity -knee can’t be fully extended
What can OA of the knee also result in? 1️⃣8️⃣
- 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
How can osteoarthritis be compartmental? 1️⃣8️⃣
Uni-, bi- or tri- compartmental
affecting 1,2 or 3 of the
- medial femorotibial compartment
- lateral femorotibial compartment
- patellofemoral compartment
What are the risk factors for knee osteoarthritis? 1️⃣8️⃣
- 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
How is knee OA treated? 1️⃣8️⃣
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)
What is septic arthritis? 1️⃣9️⃣
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
What joints does septic arthritis affect? 1️⃣9️⃣
-most commonly knee joint
- hip
- shoulder
- ankle
- wrists
What pathogens cause septic arthritis? 1️⃣9️⃣
- most commonly staph. aureus
- staph. Epidermis
- Neisseria gonorrhoea
- strep. Viridans
- strep. pneumonia
- group B streptococci
What are the risk factors for septic arthritis? 1️⃣9️⃣
- extremes of age
- diabetes mellitus
- RA
- immunosuppression
- IV drug use
Why are prosthetic joints particularly at risk of septic arthritis? 1️⃣9️⃣
-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
What is the major consequence of bacterial invasion in septic arthritis? 1️⃣9️⃣
- 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
How do patients with septic arthritis present? 1️⃣9️⃣
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
What should the joint be examined for? 1️⃣9️⃣
- 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
If septic arthritis is suspected, what should be done? 1️⃣9️⃣
- carry out joint aspiration immediately
- send aspirate for urgent microscopy, culture and sensitivities
How can patients with treated septic arthritis be affected? 1️⃣9️⃣
-50% adults will have decreased range of motion or chronic pain after infection had resolved
