S4 - Knee Conditions Flashcards
- *Femoral shaft fractures**
- Cause
- Position of each fragment
- Position
- Site and name
- Complication
- Treatment
Causes:
Usually high-velocity e.g. falls from height, or road traffic collisions
Non-accidenta injury e.g. child abuse
Risks:
Osteoporosis
Bone metastases or bone lesions (e.g. bone cysts)
- *Position:**
- Proximal fragment: often abducted due to the pull of gluteus medius and gluteus minimus on the greater trochanter. and flexed due to the action of iliopsoas on lesser trochanter
- Distal fragment: Adducted into a vrus deformity due to action of adductor muscles. and extended due to the pull of gastrocnemius on posterior femur
- *Site:**
- Proximal
- Mid-shaft
- Supracondylar
Complication:
Blood loss in closed femoral shaft fractures is 1000-1500mL and the patient may develop hypovolaemic shock
Blood loss in open femoral fractures may be double this amount
Treatment:
Femoral shaft fractures are treated with surgical fixation
- *Distal femoral fractures**
- Mechanism of injury
- Worried about which artery
- Treatment
Mechanism of injury:
Younger patient - usual mechanism is a high-energy sporting injury
Elderly patients - this type of fracture is associated with osteoporotic bone, usually elderly person falls
Worried about which artery:
Popliteal artery may become involved if there is significant displacement of the fracture and careful assessment of neurovascular status
Treatment:
Reduction of the fracture
- *Tibial plateau fractures**
- Explaining the location of the fracture
- Cause
- Mechanism of injury
- Complication/risk
Explaining the location of the fracture:
Fracture’s affecting the articulating surface of the tibia within the knee joint - they can be unicondular or bicondular
Cause:
High-energy injuries
Mechanism of injury:
Usually axial loading (‘top to bottom’) with valgus and varus angulation (an abnormal medial or laterial flexion load) of the knee
- *Complication:
- ** Articular cartilage is always damaged
- > Post-traumatic osteoarthritis in the affected joint
- *-** Can be associated with menical tears and ACL
Patellar fractures
Cause
Examination
Treatment
Cause:
Direct impact injury (e.g. knee against dashboard) or by eccentric contraction of the quadriceps
Examination:
Often a palpable defect in the patella and a haemarthrosis (blood in the joint)
Unable to perform a straight leg raise - as extensor mechanism is disrupted
Treatment:
Displaced patellar fractures require reduction and surgical fixation
Undisplaced patellar fractures can be protected through splinted and using crutches (don’t usually require surfical fixation)
Note - 8% of the population the patella is bipartie (in two parts) - this can sometimes be mistaken for a patella fracture on the x-ray. This can develop due to failure of union of a secondary ossification centre.
- *Patella dislocation:**
- Define and explanation
- Which way does the patella usually dislocate
- One major piece of anatomy that stabilises the patella
- Cause
- Predisposing factors to patella dislocation
- Treatment
# Define and explanation: Patella dislocation refers to the patella being completely displaced out of its normal alignment. Subluxation is partial displacement.
Which way does the patella usually dislocate?
Common direction for the patella to dislocate laterally
One major piece of anatomy that stabilises the patella:
The patella is 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
Cause:
Twisting injury in slight flexion or a direct blow to the knee
Predisposing factors to patella 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
Treatment:
Extending the knee then manually reducing the patella, immobilsation is used whilst healing takes place. Followed by physio to strengthen the VMO
Meniscal injuries
Mechanism
Symptoms
Examination of the patient shows
Treatment
Meniscal injuries (meniscal tears) are probably the most common type of knee injury.
Mechanism:
Sudden twisting motion of a weight-bearing knee in a high degree of flexion
Symptoms:
Intermittent pain, localised in the joint line
Knee clicking, catching, locking
Sensation of giving way
Swelling occurs as a delayed symptoms due to a reactive effusion or not at all, as menisci are largely avascular (except that of the periphery). Acute haemarthrosis is therefore rare and if present, indicates a tear in the peripheral vascular aspect of the meniscus or associate anterior cruciate ligament
Examination of the patient shows:
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
Treatment:
Acute traumatic meniscal tear - Surgically either meniscetomy or meniscal repair
Chronic degenerative process: Not surgically treated, instead managed conservatively
Collateral ligament injury
Role of collateral ligaments
Causes
Mechanism
Which is more at risk of damage
Symptoms
Test to work out which is damaged
Role of collateral ligaments:
Medial and lateral collateral ligaments normally control the lateral movement of the knee joint and brace it against unusal varus and valgus deformation
Causes:
Direct contact sports such as football
Mechanism:
Acute varus or valgus angulation of the knee
Which is more at risk of damage:
MCL is inured more commonly thanLCL, but a torn LCL has a higher change of cuasing knee instability
Symptoms:
Patient will experience pain and swelling of the knee
As the initial pain and stiffness subside, the knee joint may feel unstable and patient may complain of it giving way or not supporting their body weight
- *Test to work out which is damaged:**
- Pain on medial rotation indicates damages to the medial ligament
- Pain on lateral rotation indicates damage to the lateral ligament
Unhappy triad
‘blown knee’
Injury to Anterior cruciate ligament, medial collateral ligament, medial meniscus
Anterior cruciate ligament injury
Type of injury
Mechanism
Symptoms
Treatment
Test
hear a ‘pop’
- ACL is weaker than the PCL and is more commonly injured
Type of injury:
Non-contact injury
Large force to the back of the knee with the joint partly flexed
Mechanism:
ACL is usually torn as a result of a quick deceleration, hyperextension or rotational injury e.g. following a sudeen change of direction during sport
Symptoms:
- Patient typically reports feeling a popping sensation in their knee with immediate swelling
- When the pain has subsided, the patient experiences instability of the knee as the tibia sides anterioly under the femur
- ‘giving way’ sensation
Treatment:
For patients with low functional demands on their knee, can function well with a ruptured ACL
Sportsmen will often need surgical reconstruction
Test:
Anterior Drawer Test, attempt to pull the tibia forwards, if it moves, the ligament has been torn
Posterior Cruciate Ligament
Mechanism and cause
Treatment
Test
Mechanism and causes
Knee is flexed and a large force is applied to the upper tibia, displacing it posteriorly
Severe hyperextension injury
e.g. The road traffic collisions when the proxiaml leg collides with the dashboard
e.g. The seen in road traffic collisions when the proximal leg collides with dashboard
e.g. The player falls on a flexed knee with their ankle in plantarflexed - The tibia hits the ground first and is displaced posteriorly
Treatment:
Tibia can be displaced posteriorly on the femur. PCL injuries respond well to conservative management with bracing and rehabilitation
Test:
PCL -
Posterior draw test - where the clinician holds the knee in a fixed position, if there is movement, the ligament has been torn
- *Dislocation of the knee joint:**
- Cause
- Risk
- Essential investigation
Cause:
High energy trauma
To dislocate the knee joint, at least three of four ligaments (MCL, LCL, ACL, PCL) must be ruptured
Risk:
Arterial injury is very common because the 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
*Essential investigation:
Due to injury to the popliteal artery, must fully assess the vasculature of the leg e.g. with Magnetic Resonance Angiography
- *Swellings around the knee**
- The swellings can be…
o Bony e.g. Osgood-Schlatter’s disease (see below)
o Soft tissue
Localised e.g. an enlarged popliteal lymph node; a popliteal artery
aneurysm
Generalised e.g. lymphoedema of the lower limb
o Fluid
Inside the joint = effusion
Outside the joint = soft tissue haematoma
Knee effusion
# Define and explain: An effusion is an accumulation of fluid inside the knee joint; it is never normal. The adjacent image shows an effusion of the left knee.
2 types of effusions:
Effusions can be acute (defined as < 6 hours after injury e.g. after cruciate ligament rupture) or delayed (> 6 hours after injury).
One complication if ACL ruptures:
In an ACL rupture, bleeding often occurs inside the joint; this is referred to as a haemarthrosis.
Inflammation of the synovium can lead to swelling of the knee:
Delayed swelling of the knee (e.g. the day after injury) is usually due to reactive synovitis. Inflammation of the synovium, in response to injury, leads to the production of an increased volume of synovial fluid.
Acute knee effusions can be divided into:
Haemarthrosis (blood in the joint). Diagnostically, a haemarthrosis is an ACL rupture until proven otherwise.
Lipo-haemarthrosis (blood and fat in the joint). A lipohaemarthrosis is a fracture until proven otherwise as the fat has usually released from the bone marrow.
X-ray:
In a lipo-haemarthrosis, a fat-fluid interface can be seen on the X-ray (see arrow on image below). Fat is less dense than blood, absorbs fewer X-rays and therefore appears darker than blood on the X-ray film. In this X-ray, there is a tibial plateau fracture; it is difficult to see on the X-ray but the presence of a lipohaemarthrosis
gives the radiologist a strong indication that a fracture is present. (x-ray pic attached)
- *Bursitis of the knee**
- Explanation
- Name the 5 bursa’s
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 (deep to the common insertion of the
sartorius, gracilis and semitendinosus tendons), and the suprapatellar bursa.
- *Pre-patellar bursitis**
- Cause
- What cause the swelling
- Symptoms
- Popular name
Cause:
Often caused by pressure from constant kneeling e.g. carpet layers, roofers
What causes the swelling:
Inflammation of this bursa, however, results in a marked increase of fluid within the space -> synovial fluid
Symptoms:
Knee pain and swelling
Erthema overlying the inflammed bursa
Difficult to walk due to the pain
Will not be able to kneel on the affected side
History of repetitive trauma to the bursa such as may occur during scurbbing the floor –> Housemaid’s knee (housemaid’s tend to learn forwards on their knees whilst scrubbing, it is the pre-patellar bursa that tends to be inflammed)
Infrapatellar bursitis
Cause
What is meant by infrapatellar bursa
Popular name for this condition
Cause:
Prolonged/repetitive from constant upright kneeling
What is meant by infrapatellar bursa?
Essentially consists of two bursae, one of which sits superficially between the patella tendon and the skin and the second referred to as the deep infrapatellar bursa is sandwiched between the patella tendon and tibia bone. Bursitis most commonly affects affects superficial infrapatellar bursa
Popular name is:
Clergyman’s knee
- *Suprapatellar bursitis**
- Overall common cause of this
- Causes of knee e________
The suprapatellar bursa is an extension of the synovial cavity of the knee joint. A knee effusion therefore often presents with swelling in the suprapatellar pouch (the suprapatellar bursa extends superiorly from beneath the patella under the quadriceps muscle).
Hence, rather than being a sign of localized irritation,”suprapatellar bursitis” is more usually a sign of significant pathology in the knee joint.
Causes of a knee effusion include:
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).
- *Semimembranosus bursitis**
- Similarities with one of the types of bursitis
- What exactly happens leading to this bursa to swell
- Other names used
Similarities with one of the types of bursitis:
Like suprapatellar bursitis, fluid is the semimembranosus bursa is an indirect consequence of swelling within the knee joint.
Location:
The semimembranosus bursa is located beneath the deep fascia of the popliteal fossa in the interval between the semimembranosus muscle and the medial head of the gastrocnemius muscle.
What exactly happens leading to this bursa to swell:
It is 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.
Other names used:
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)
What exactly is this?
When does it commonly occur?
Symptoms
Treatment and long-term
What exactly is this?
OSD is inflammation of the apophysis (site of insertion) of the patellar ligament into the tibial tuberosity.
When does it commonly occur?
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.
Symptoms:
Patients complain of intense knee pain during running, jumping, squatting, ascending and descending stairs and during kneeling.
Treatment and long-term:
OSD usually resolves with rest and ice. The pain and swelling resolve at the age of skeletal maturity when the apophysis (which has a separate ossification centre) fuses. However, the bony prominence usually remains permanently.
Osteoarthritis of the knee
Symptoms
Deformity of the kneee
Risk factors
Treatment ladder
Symptoms:
The typical symptoms of knee osteoarthritis are knee pain, stiffness and swelling.
The pain may follow a pattern, for example:
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.
Loss of articular cartilage leads to friction as bone rubs on bone during movement. Increased friction leads to crepitus (grating sound)
Deformity of the knee: (picture below)
Deformity at the knee joint is common with osteoarthritis. For example, the patient may develop a varus deformity (deviation of the distal component toward the midline; see image below), a valgus deformity (deviation away from the midline) or a fixed flexion deformity (in which the knee cannot be fully extended)
Risk factors:
Age, female sex, previous trauma on the joint, obesity, family history of OA, having another condition affecting joint e.g. RA, gout, septic arthritis, haemophilia with haemoarthrosis (bleeding into a joint)
Treatment ladder:
Same as OA of the hip (S3)
Septic arthritis of the knee
- What is this
What is this?
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.
Pathogen - most commonly..
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.
Risk factors
Extremes of age, diabetes mellitus, rheumatoid arthritis, immunosuppression and intravenous drug abuse, prosthetic joint (joint replacements) are at big risk (either intra-operative contamination or haematogeneous spread from a distant infective focus e.g. during dental surgery), patient may not be symptomatic for months-years after operation
Major consequences of bacterial invasion…
Damage to articular cartilage, either due to the organism’s pathologic properties or to the host’s immune response
Symptoms and signs:
Fever (40-60% of cases)
Pain (75%)
Reduced range of motion.
The symptoms may evolve over a few days to a few weeks. The fever is usually low grade with rigors present in only 20% of cases.
Joint should be examined for erythema (redness), swelling (90% have an obvious effusion), warmth, tenderness, and limitation of active and passive range of motion.
If suspect septic arthiritis:
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.
