Knee Disorders

Question 1

What are the 3 standard views used for a knee X-Ray

Answer 1

Anterior-Posterior
Lateral
Skyline (Superiorly, with knee flexed)

Question 2

What usually causes femoral shaft injuries in young adults and healthy children

In closed femoral shaft fractures, how much blood is lost and what may the patient develop

Answer 2

High velocity trauma

1000-1500ml, may develop hypovolaemic shock

Question 3

In a femoral fracture, how does the proximal fragment appear and what muscles cause this

How does the distal fragment appear and what muscles cause this

Answer 3

Abducted- Gluteus medius and minimus
Flexed- Iliopsoas

Adducted- Adductor muscles
Extended- Gastrocnemius

Question 4

What is the usual cause of a distal femoral fracture in young patients
Which artery may be involved

Answer 4

High energy- sporting injury, popliteal artery

Question 5

• What is the usual cause of a Tibial Plateau Fracture
• What is affected in this kind of fracture
• Are they uni or bicondylar
• Which condyle is most commonly affected
• What 2 injuries are associated with these fractures

Answer 5

• Axial loading with varus/ valgus angulation of the knee
• Articulating surfaces of tibia within the knee joint
• Can be both
• Lateral tibial condyle
• Meniscal tears and ACL injuries

Question 6

What 2 things can cause patellar fractures
What is the most common age range for these
What are 3 signs of a patellar fracture

Answer 6

Direct impact injury
Eccentric contraction of quadriceps
20-50 years

Palpable defect in patella
Haemarthrosis (Blood in joint)
Patient unable to perform a straight leg raise

Question 7

Compare treatment of displaced and undisplaced patella fractures

Answer 7

Displaced: Reduction and surgical fixation
Undisplaced: Splints and crutches, surgery not usually needed

Question 8

What can be mistaken for a patellar fracture

What causes this

Answer 8

A bipartite patella (8% of population)

Failed union of a secondary ossification centre within patella body

Question 9

Compare patella dislocation and Subluxation

What’s the most common cause of patellar dislocation, and the mechanism

Answer 9

Dislocation: Patella completely displaced
Subluxation: Partially displaced

Trauma (Twisting injury/ direct impact)
Medial rotation of femur on a planted foot while knee is flexed

Question 10

Identify 5 factors that can lead to patellar dislocation

Answer 10

Ligamentous laxity 
Weak quadriceps muscles 
Shallow trochlear groove 
Long patellar ligament 
Previous dislocations

Question 11

Describe the treatment for patellar dislocation

Answer 11

Extend the knee, manually reduce the patella

Immobilise during healing, then physiotherapy to strengthen the VMO

Question 12

How do meniscal injuries occur

Name 5 symptoms

Answer 12

Sudden twisting motion of a weight bearing knee in a high degree of Flexion

• intermittent pain
• knee clicking
• knee locking (can’t fully extend due to Intra-articular foreign body)
• delayed swelling may present
• knee ‘giving way’ (tibia slides anteriorly under femur)

Question 13

Name 2 things that can be found on examination in a meniscal injury

Answer 13

• Joint line tenderness

- Reduced motion due to pain/ swelling

Question 14

Why does an Injured Lateral Collateral Ligament have a higher chance of causing knee instability

What is the Unhappy Triad

Answer 14

Because medial tibial plateau forms a deeper, more stable socket than the lateral condyle

Injured ACL, MCL and Medial Meniscus caused by strong force to knee from lateral side.

Question 15

Which Cruciate ligament is weaker and more commonly injured

List 4 causes of this being injured

Answer 15

ACL

• Quick deceleration
• Hyperextension
• Rotational injury
• Large impact to back of partially flexed knee

Question 16

The ACL prevents medial rotation of an extended knee. Describe effects of a torn ACL on lateral and medial tibial condyles

What does this lead to and what is this called

Answer 16

• Medial tibial condyle rotates internally
• Lateral tibial condyle subluxes anteriorly

Reduction of lateral tibial condyle occurs with a sudden ‘slip’ when knee is flexed.

Anterolateral rotatory instability

Question 17

What is the most common mechanism of PCL injury

Name 2 tests used to detect an ACL Injury
Name 1 test used to detect a PCL injury

Answer 17

A ‘dashboard injury’- Large force applied to proximal tibia when knee is flexed

ACL: Lachman’s Test, Anterior Drawer Test
PCL: Posterior Drawer Test

Question 18

How many of the 4 main ligaments must be injured for a knee dislocation to occur

Which artery is most at risk and why
Name 3 ways it can be injured

Answer 18

At least 3
Popliteal as it is very immobile

• May tear
• Crushed
• Traction injury (endothelial damage-> Thrombosis)

Question 19

What are 3 types of knee swelling

Answer 19

Bony
Soft tissue (Localised OR Generalised)
Fluid

Question 20

What is a knee effusion

What are the 2 types

Answer 20

Accumulation of fluid inside knee joint

Acute/ delayed (> hours after injury)

Question 21

What are 2 types of acute knee effusion

What is the initial suspected cause for each

Answer 21

Haemarthrosis: Blood in joint- ACL rupture

Lipo-haemarthrosis: Blood and fat in joint- Fracture

Question 22

Which 5 knee Bursae are most commonly inflamed

Answer 22

Prepatellar bursa
Infrapatellar bursa (Deep and subcutaneous)
Subsartorial bursa (Pes Anserinus bursa)
Suprapatellar bursa

Question 23

Identity 4 signs of Pre-patellar bursitis

Identify 3 causes, and suggest an alternate name for this type of bursitis

Answer 23

Knee pain + swelling
May be erythema
Difficulty walking
Unable to kneel

Repetitive trauma (E.g floor scrubbing)
Falling onto knee
Blunt trauma to knee

“Housemaid’s knee”

Question 24

In Infrapatellar bursitis, which is bursa is most commonly affected

What is the usual cause of Infrapatellar bursitis and what is another name for Infrapatellar bursitis

Answer 24

Most common- Superficial Infrapatellar Bursa

Repeated micro trauma caused by activities involving kneeling

Clergyman’s Knee

Question 25

Why does a knee effusion caused suprapatellar bursitis

Name 5 causes of knee effusion

Answer 25

The SP bursa is an extension of the synovial cavity of the knee joint

• Osteoarthritis
• Rheumatoid arthritis
• Gout and pseudogout
• Infection
• Repetitive microtrauma

Question 26

Why does a knee effusion caused Semimembranosus bursitis

What are 2 other names for this swelling

Answer 26

SM Bursa is connected to knee joint, so fluid can enter the SM Bursa.

Popliteal cyst (As popliteal fossa swells)
Baker’s cyst

Question 27

What is Osgood-Schlatter’s disease (OSD)
Who does it occur in, is it bilateral or unilateral

What are 6 symptoms
What is the treatment

Answer 27

Inflammation of apophysis of patellar ligament into tibial tuberosity

In sporty teenagers, can be bilateral

Knee pain during running/ jumping/ squatting/ kneeling/ stairs
Swelling
Rest and ice

Question 28

What is septic arthritis
What are the most common locations
What is the most common organism that causes it
List 5 risk factors

Answer 28

Invasion of joint space by micro-organisms
Knee then Hip
Staph Aureus

Age
Diabetes 
Rheumatoid arthritis 
Immunosupression 
IV drug abuse

Question 29

What 2 things increase the risk of infection from a prosthetic joint replacement-> Septic arthritis

Answer 29

Biofilm produced by Staph epidermidis protects it

Cement used in joint replacement inhibits WBC function

Question 30

What are the 3 symptoms of septic arthritis

What can be seen in infection of a prosthetic joint

Answer 30

Fever, pain, reduced range of motion

Slight swelling + draining sinus

Question 31

What should be done if septic arthritis is suspected

Answer 31

Aspiration of the joint immediately

Aspirate sent for urgent microscopy, culture and sensitivities