The Lower Limb (2)- The knee, femoral triangle, anterior thigh and medial thigh Flashcards
femoral shaft fractures
- Signs and symptoms
- treatment
The patient will have a tense swollen thigh. Patient may develop hypovolaemic shock. The blood loss in open femoral fractures may be double this amount.
Femoral shaft fractures are treated with surgical fixation.
mechanism of injury of distal femoral fracture
The usual mechanism is a high-energy sporting injury and there is often significant displacement of the fracture fragments.
In the elderly, this type of fracture is usually seen in association with osteoporotic
bone; the usual mechanism in the elderly is a fall from standing.
how tibial plateau fracture occur
Tibial plateau fractures also tend to be high-energy injuries. The usual mechanism is axial (‘top to bottom’) loading with varus or valgus angulation (an abnormal medial or lateral flexion load) of the knee.
The articular cartilage is always damaged
most patients will develop a degree of post-traumatic
osteoarthritis in the affected joint.
unhappy triad
The unhappy triad (or ‘blown knee’) is an
injury to the anterior cruciate ligament,
medial collateral ligament and medial
meniscus. This results from a strong
force applied to the lateral aspect of the
knee. The medial meniscus is firmly
adherent to the medial collateral
ligament, which is why it is also injured.
patella fractures
They are either caused by a
direct impact injury (e.g. knee against
dashboard) or by eccentric contraction of the
quadriceps
how to tell patella is fractured
On examination, there
is often a palpable defect in the patella and a
haemarthrosis (blood in the joint).
If the extensor mechanism is disrupted (i.e.
the fracture completely splits the patella
distal to the insertion of the quadriceps
tendon), the patient will be unable to
perform a straight leg raise i.e. to lift the leg
off the bed by flexing at the hip and keeping
the knee extended
treatment of patella fractures
Displaced patellar fractures require reduction and surgical fixation.
Undisplaced patellar fractures can be protected whilst healing takes place
through splinting and using crutches, and do not usually require surgical
fixation.
subluxation
partial displacement
factors that predispose the patella to dislocate
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
treatment of patella dislocation
The treatment involves extending the knee then manually reducing the patella.
Immobilisation is used whilst healing takes place, and this is followed by physiotherapy
to strengthen the Vastus medialis obliquus
most common type of knee injury
meniscal injuries
how do meniscal injuries occur
typically occur during a sudden twisting motion of a weight-bearing knee in a high degree of flexion
symptoms of meniscal injuries
- intermittent pain, localised to the joint line,
- knee clicking, catching, locking (inability to fully extend the knee due to an intra-articular foreign body)
- sensation of giving way.
- Swelling occurs as a delayed symptom due a reactive effusion or not at all, as the menisci are largely avascular (except at their periphery).
-Acute
haemarthrosis indicates a tear in the peripheral
vascular aspect of the meniscus or an associated injury to the anterior cruciate
ligament.
- A chronic effusion (increased synovial
fluid) can occur due to synovitis (inflammation of the synovial membrane).
treatment of meniscal injury
-surgically by either
meniscectomy or meniscal repair.
-conservative management is increasingly being recommended for these.
why is conservative management becoming a more common treatment for meniscal injury
there is increasing evidence that
meniscal tears that result from a chronic degenerative process within the knee
have a similar prognosis with conservative management as with surgery. Hence,
conservative management is increasingly being recommended for these.
what prevents excessive posterior motion of the tibia on the femur
Together, the collateral ligaments also work with the
posterior cruciate ligament (PCL) to prevent excessive
posterior motion of the tibia on the femur.
varus
medial angulation of the distal segment
valgus
lateral angulation of the distal segment
remember vaLgus Lateral
acute valgus strain
The medial collateral ligament (MCL)
is at risk and in varus strain the lateral collateral ligament (LCL) is at risk. The MCL is
injured more commonly than the LCL, but a torn LCL has a higher change of causing
knee instability.
which collateral ligament is at risk in valgus/varus strain and why
medial collateral ligament
lateral
which collateral ligament is injured more commonly
The MCL is
injured more commonly than the LCL. This is because the medial tibial plateau forms a deeper and more
stable socket for the femoral condyle than the lateral tibial plateau
symptoms of Collateral Ligament injury
Immediately after the injury, the patient will experience pain and swelling of the
knee. As the initial pain and stiffness subside, the knee joint may feel unstable and
the patient may complain of it giving way or not supporting their body weight.
which cruciate is weaker and more commonly injured
the anterior
what causes the anterior cruciate ligament to be injured
usually torn as a result of a quick
deceleration, hyperextension or rotational injury
It is usually a non-contact injury
The ACL can also be torn by application of a large force to the back of the knee with the joint partly flexed.
symptoms of ACL injury
The patient typically reports feeling a popping sensation in their knee with
immediate swelling. When the swelling has subsided, the patient experiences
instability of the knee as the tibia slides anteriorly under the femur. Patients tend
to describe this as the knee ‘giving way’.
anterolateral rotatory instability
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
anteriorly. 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’
treatment of ACL injury
surgical reconstruction if used often
causes of PCL injury
‘dashboard injury’; the knee is flexed and a large force is applied to the upper tibia, displacing it posteriorly.
The PCL can also be torn during football when the player falls on a flexed knee with their ankle plantarflexed. The tibia hits the ground first and is displaced posteriorly, avulsing the PCL.
A tackle with the knee flexed can also cause this
injury.
Finally, a severe hyperextension injury can also avulse the PCL from its insertion on the posterior aspect of the intercondylar area.
what has to be done for the knee to dislocate
To dislocate the knee joint, at least three of the four ligaments
(MCL, LCL, ACL and PCL) must be ruptured.
what is often associated with a dislocation of the knee joint
popliteal artery is
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
what can cause swellings around the knee
bony
soft tissue
fluid
bony swellings of knee
Bony e.g. Osgood-Schlatter’s disease
soft tissue swellings of the knee joint
o Localised e.g. an enlarged popliteal lymph node; a popliteal artery
aneurysm
o Generalised e.g. lymphoedema of the lower limb
fluid swelling of the knee joint
o Inside the joint = effusion
o Outside the joint = soft tissue
haematoma
what is an effusion
An effusion is an accumulation of fluid inside the knee joint; it is never normal.
Effusions can be acute (defined as < 6 hours after injury e.g. after cruciate
ligament rupture) or delayed (> 6 hours after injury)
haemarthrosis
bleeding inside the joint
ACL rupture until proven otherwise
what causes delayed swelling of the knee
usually due to reactive synovitis. Inflammation of the synovium in response to injury. Leads to production of an increased volume of synovial fluid
lipo-hemarthrosis
(blood and fat in the joint). A lipo-haemarthrosis is a
fracture until proven otherwise as the fat has usually released from the
bone marrow.
bursitis of the knee
Bursitis is inflammation of a bursa. The bursae of the knee that are most commonly inflamed are the prepatellar bursa, infrapatellar bursa, pes anserinus bursa and the suprapatellar bursa
pre-patellar bursa
The pre-patellar bursa is a superficial bursa with a thin synovial lining, located
between the skin and the patella.
symptoms of of pre patellar bursa
The patient usually presents with knee pain and swelling. There may be some
erythema overlying the inflamed bursa. The patient finds it difficult to walk due to
the pain and will not be able to kneel on the affected side.
infrapatellar bursitis
occurs due to repeated microtrauma caused by
activities involving kneeling. The popular name clergyman’s knee, reflects the
more upright position of kneeling that generally triggers this condition.
infrapatellar bursa
occurs due to repeated microtrauma caused by
activities involving kneeling. The popular name clergyman’s knee, reflects the
more upright position of kneeling that generally triggers this condition.
what does bursitis most commonly affect
superficial infrapatellar bursa
causes of knee effusion
Osteoarthritis
Rheumatoid arthritis
Infection (septic arthritis; see below)
Gout and pseudogout
Repetitive microtrauma to the joint (as a result of running on soft or
uneven surfaces).
suprapatella bursa
extension of the synovial cavity of the knee joint
semimembranosus bursitis
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. The resulting swelling in
the popliteal fossa is known as semimembranosus bursitis or more commonly
as a popliteal cyst or Baker’s cyst.
Osgood-Schlatter’s disease
OSD is inflammation of the apophysis (site of insertion) of the patellar ligament
into the tibial tuberosity.
OSD most commonly occurs in teenagers who play sport (running and jumping)
and causes localised pain and swelling. It is bilateral in 20-30% of cases.
crepitus
a grating sound and crackling sensation on movement of the joint
septic arthritis of the knee
Septic arthritis is 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.
what pathogens cause 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.
symptom of septic arthritis
Fever (40-60% of cases)
Pain (75%)
Reduced range of motion
treatment of septic arthritis
Aspiration of the joint should be carried out
immediately and the aspirate should be sent for urgent microscopy, culture and
sensitivities.
Septic arthritis carries a high morbidity, even if treated optimally.
which tibial plataeu fractures are most common
They can be unicondylar (affecting one condyle) or bicondylar (affecting
both tibial condyles). Fractures affecting the lateral tibial condyle are the most
common.
