Knee Dislocations and Fractures

Question 1

The knee is an articulation between which bones?

Answer 1

Distal femur and proximal tibia

Question 2

The medial collateral ligament of the knee resists which type of stress?

Answer 2

Valgus

Question 3

In which instance do distal femoral fractures usually occur?

Answer 3

1. Osteoporotic bone
2. Fall onto flexed knee

Question 4

Which two categories can distal femoral fractures fall into?

Answer 4

1. Intracapsular (intercondylar)
2. Extracapsular (supracondylar)

Question 5

Why will a distal femoral fracture usually adopt a flexed position?

Answer 5

Pull of gastrocnemius muscles

Question 6

Why is it preferrable to treat a distal femoral fracture with a plate and screws versus a cast?

Answer 6

The fracture position is difficult to maintain in a cast

Question 7

For which main reasons is a true knee dislocation considered a surgical emergency?

Answer 7

1. High incidence of vascular injury
2. Nerve injury
3. Compartment sydrome

Question 8

How can the vascular status of the knee be examined after dislocation?

Answer 8

1. Doppler
2. Duplex scan
3. Angiogram

Question 9

Virtually all patellar dislocations are _________

Answer 9

Virtually all patellar dislocations are lateral

Question 10

In which type of patient is a patellar dislocation most common?

Answer 10

Adolescent females

Question 11

In which two ways is a patellar dislocation most likely to reduce?

Answer 11

1. Spontaneously when the knee is straightened
2. During manipulation

Question 12

Patellar dislocations are predisposed to by which main factors in adolescents, especially females?

Answer 12

1. Generalised ligamentous laxity
2. Valgus alignment of the knees
3. Rotational malalignment (including femoral neck anteversion)
4. Shallow trochlear groove

Question 13

Where will patients have tenderness after a patellar dislocation?

Answer 13

Over medial retinaculum

(where medial patellofemoral ligament is torn)

Question 14

For which reason is a patellar dislocation most likely to cause a haemarthrosis?

Answer 14

Impactation of medial patellar facet on outer aspect of lateral femoral condyle

Question 15

Around __% of first time patellar dislocations will experinece a further dislocation and __% of those will have multiple recurrent dislocations

Answer 15

Around 10% of first time patellar dislocations will experinece a further dislocation and 50% of those will have multiple recurrent dislocations

Question 16

How can further patellar dislocations be prevented?

Answer 16

Temporary splintage followed with physiotherapy

(physiotherapy is key to strengthen vastus medialis)

Many adolescent patients stabilise with time

Surgical stabilisation is rarely required

Question 17

Tibial plateau fractures usually occur in which two scenarios?

Answer 17

1. High energy in younger patients
2. Low energy in elderly and osteoporotic

Question 18

What are tibial plateau fractures?

Answer 18

Intra-articular fractures with either a split in the bone, depression of the articular surface or both

Classified via the Schatzker system

Question 19

How can tibial plateau fractures be treated generally?

Answer 19

Reduction of articular surface, rigid fixation followed by early motion

Question 20

Which type of injury may induce a lateral tibial plateau fracture, and which knee ligaments are most likely to be affected?

Answer 20

Valgus stress injury

MCL and possibly ACL

Question 21

Injury to which nerve will induce foot drop, and which muscle is affected?

Answer 21

Common fibular (peroneal) nerve

Tibialis anterior

Question 22

A medial tibial plateau fracture will be induced by which type of injury to the knee?

Answer 22

Varus stress

Question 23

In tibial plateau fractures which are depressed, fractures must be raised back to normal and in order to do this, what is used to fill the void in the bone?

Answer 23

Bone grafting

Usually morsellised packed cancellous autograft from the iliac crest

Question 24

What are the two major options for definitive management of high energy proximal tibial fractures?

Answer 24

1. Open reduction and internal fixation
2. External fixation (ring fixator and fine wires to hold fracture fragments under tension)

An external fixator is often required initially for initial stability and to allow swelling to reduce before definitive management

Question 25

Failure to restore the articular surface at the proximal tibia after fracture usually results in what?

Answer 25

Total knee replacement