Disorders of the knee Flashcards
What is the main way a femoral shaft fracture occurs in children?
High velocity trauma
What is one of the main risks of a femoral shaft fracture?
The patient may go into hypovolaemic shock as 1,000- 1,500 ml of blood is lost
Where does a tibial plateau fracture occur?
On the articulating surface of the tibia with the knee
What kind of tibial plateau fracture is the most common?
Fracture of the LATERAL tibial condyle
What will a patient with a complete patellar fracture, distal to the insertion of the quadriceps be unable to do?
Unable to perform a straight leg raise
When looking at an X-ray of a patella, why must you be careful when diagnosing a patellar fracture?
A bipartite patella - present in 8% of the population Can be mistaken for a patellar fracture
What does subluxation of the patella mean?
A partial displacement of the patella
What is the most common direction for the patella to displace?
Laterally
How does a patella dislocation most commonly occur?
From a sudden change of direction playing sports
The femur internally rotates on a planted foot whilst the knee is flexed
Name some predisposing fractures for patellar dislocation
- Generalised ligament laxity
- Weak quadriceps muscles (especially the VMO)
- Shallow trochlear groove with a flat lateral lip
- Long patellar ligament
- Previous dislocation
What is the most common kind of knee injury?
A meniscal tear
What kind of symptoms might a patient report if they had a meniscal injury?
- Intermittent pain localised to the joint line
- Knee may ‘click’, ‘latch’ or ‘lock’
Which ligament is at risk in acute valVus strain?
The Medial Collateral Ligament
Which ligament is at risk in acute vaRus strain?
The Lateral Collateral Ligament
What force does the lateral collateral ligament resist?
Valgus force
What force foes the medial collateral ligament resist?
Varus force
Which collateral ligament is injured more commonly and why?
The MCL
It has a broader attachment and is attached to the collateral ligament which makes it more rigid, therefore easier to damage
Which collateral ligament has a higher chance of causing knee instability?
The LCL
What 3 things are injured in the Unhappy Triad (Blown Knee)?
- ACL
- MCL
- Medial Meniscus
Describe the kind of motion that usually causes the ACL to tear
Sudden deceleration, hyperextension or rotational injury - not usually injured in contact sports
What is the most common mechanism of a PCL injury?
Dashboard injury - flexed knee colliding with dashboard in a RTA or falling on a fixed knee in sport
Name the 2 tests that can be used to test for ACL/ PCL injury
- Lachman’s test
- Draw test
Which ligaments need to be torn for the knee to dislocate?
At least 3 of either:
- ACL
- PCL
- MCL
- LCL
Which artery is commonly injured if the knee dislocates?
Popliteal artery
Define ‘acute’ and ‘delayed’ knee effusions
acute = <6 hours after injury
delayed = >6 hours after injury
How can acute knee effusions be divided?
- Haemarthrosis - blood in the joint (diagnostically an ACL injury unless proven otherwise)
- Lipo-haemarthrosis - blood and fat in the joint (diagnostically a fracture unless proven otherwise as fat is released from bone marrow)
What bursae is inflamed in Housemaid’s knee?
Pre patellar bursa
What bursae is inflamed in Clergyman’s knee?
Infrapatellar bursa
Name some causes of Suprapatellar bursitis
- Osteoarthritis
- RA
- Infection
- Gout or pseudo gout
- Repetitive microtrauma (running on uneven surfaces)
Describe how Baker’s cyst or semimembranous bursitis occurs
If the knee joint is inflamed, effusion can force itself out of a small opening between the knee joint into the semimembranous bursa
Causes a swelling on the back of the knee
What is Osgood- Schlatter’s Disease?
Inflammation of site of insertion of the patellar ligament into the tibial tuberosity
What group of people does Osgood-Schlatter’s most commonly occur in?
Sporty teenagers
Bilateral in most cases
What symptoms might a patient describe in Osteoarthritis of the knee?
- pain that comes and goes
- pain precipitated by kneeling,bending, squatting etc
- pain and stiffness that is worse after prolonged rest
What is septic arthritis?
Invasion of the joint space by micro-organisms mainly staph. aureus
What is the symptom triad of patients with septic arthritis?
- Pain
- Fever
- Reduced range of motion
Why do meniscal tears heal poorly?
Poor blood supply
Why may patients with a torn meniscus present with a ‘locked knee’?
Large fragment of the meniscus can get caught in the knee mechanism of the knee
