Knee

Question 1

Do all of the menisci have a blood supply?

What is the consequence of this for healing of tears?

Answer 1

The meniscus only has a blood supply to the outer third, so only tears in the outer third will heal. There is no point in repairing the inner 2/3 with stitches as it will not heal.

Question 2

How do the MCL and LCL ligaments differ in shape?

Answer 2

The medical collateral ligament is broad and flat with a rich blood supply and readily heals.
The LCL is like a thin and rope and has a poor blood supply.

Question 3

What is the role of the menisci?
How does the shape of the medial vs lateral menisci differ?
What is another important difference between the two?
Why is the medial compartment under a greater amount of sheer stress?

Answer 3

Menisci distribute load from convex femoral condyles to relatively flat tibial articular surfaces
Medial plateau slightly more concave
Medial meniscus is fixed whilst lateral meniscus is more mobile – this means that the medial is more prone to tear
Due to shape and soft tissues, knee pivots on medial compartment through flexion and extension – tibia internally rotates on flexion and externally rotates on extension

Question 4

What is the function of
MCL?
LCL?
ACL? (Two)
PCL? (Two)

Answer 4

MCL resists valgus stress
LCL resists varus stress
ACL resists anterior subluxation of the tibia and internal rotation of the tibia in extension
PCL resists posterior subluxation of the tibia i.e. anterior subluxation of the femur and hyperextension of the knee

Question 5

Which ligaments resist external rotation of the tibia in flexion?

Answer 5

The posterolateral corner – the PCL and LCL with popliteus and other smaller ligaments

Question 6

What type of instability may rupture of the following lead to?
MCL
ACL
PCL
Posterolateral corner
Multiligament injury

Answer 6

MCL - valgus instability
ACL - rotatory instability
PCL - recurrent hyperextension + instability decending stairs
Posterolateral corner - varus and rotatory instability
Multiligament injury can lead to gross instability

Question 7

What are the four main types of meniscal tear?

Answer 7

Longitudinal
Bucket handle
Radial
Parrot beak

Question 8

Which type of meniscal tear would you expect to heal and why?

Answer 8

Longitudinal - occurs in the outer third, where there is good blood supply

Question 9

What functional problem do bucket handle tears cause?

What long term problem may this cause?

Answer 9

Locked leg

Risk of permanent flexural deformity if left for >6 weeks

Question 10

What are the the main causes of meniscal injury?

What other ligamnet injury are meniscal tears associated with?

Answer 10

Sporting injury
Getting up from squatting position
Spontaneous degenerate tears
50% of ACL ruptures have meniscal tear

Question 11

How are soft tissue injuries of the knee investigated?

Answer 11

MRI

Question 12

What causes pain in meniscal tear?

Answer 12

When you tear the meniscus, shock absorbance puts more pressure on the bone heads, which have a rich nerve supply; meniscus itself doesn’t have any nerve innervation.

Question 13

When should you consider arthroscopic menisectomy?

Answer 13

Mechanical symptoms (painful catching or locking) or irreparable tears or failed meniscal repair.

Question 14

Treatment for bucket handle tear of meniscus?

Answer 14

Urgent surgery

Question 15

How are ligament injuries graded?

Answer 15

Grade 1 – sprain – tear some fibres but macroscopic structure intact
Grade 2 – partial tear - some fascicles disrupted
Grade 3 – complete tear

Question 16

What is the most common knee injury?

Answer 16

MCL tear

Question 17

MCL tear
Good or bad healing prospects?
What symptoms do patients have?

Answer 17

Healing is expected in the majority of partial and complete tears and little or no instability.
Patients may have laxity and pain on valgus stress with tenderness over the origin or insertion of the MCL.

Question 18

MCl tear
How are acute tears treated?
How long does it take for pain to settle?
How can chronic MCL instability be treated?

Answer 18

Acute tears are usually treated in a hinged knee brace.
MCL usually heals well, even if there is a complete tear, unless there is ACL or PCL rupture.
Pain can take several months to settle.
Chronic MCL instability can be treated with MCL tightening (advancement) or reconstruction with tendon graft.

Question 19

Which ligament is the main stabilizer against internal rotation of the tibia?
What is rupture of this ligament caused by?

Answer 19

ACL

Rupture is usually caused by sporting injury e.g. rugby, football, skiing.

Question 20

What is the rule of thirds in ACL rupture?

Answer 20

1/3 compensate and are able to function well
1/3 can avoid instability by avoiding certain activities
1/3 do not compensate and have frequent instability or can’t get back to high impact sport

Question 21

Management of ACL rupture
Is surgery always required?
What can you do to the muscles to help?
Success of ACL repair?
Where can autograft come from

Answer 21

ACL rupture doesn’t mean you definitely need surgery – older patients are more likely to compensate or avoid high impact sports
Strengthening the muscles can help – i.e. compensation for deficient ligaments; ACL can also tick to PCL to give some stability
ACL repair doesn’t work - reconstruction only
Patellar tendon or hamstrings

Question 22

When is ACL surgery indicated?
What is another benefit of ACL surgery?
What does it do for pain and long term risk of OA?

Answer 22

Rotatory instability not responding to physio
Protect meniscal damage – if you don’t do surgery then you might get a consequent bucket handle tear due to instability
Does not treat pain
Does not prevent arthritis

Question 23

LCL injury
Common or not?
Cause by?
Healing prospects?
Consequence of this?
Which other structure can be affected?
What does it often occur in combination with?

Answer 23

This is relatively uncommon
It is caused by excessive varus and hyperextension
LCL doesn’t heal and can cause varus and rotatory instability
Posterior structures are stretched, including the common perineal nerve, which can result in common peroneal nerve palsy ->foot drop
Often occurs in combination with PCL or ACL injury

Question 24

Management of complete LCL rupture?

Answer 24

Complete rupture needs urgent repair; if you get in early enough then you can repair it; if later then you have to do reconstruction with hamstring or another tendon

Question 25

PCL rupture
What can you see on examination?
What causes it?
Symptoms?
Common or rare?
Which type of instability does it cause?
When is surgery indicated?

Answer 25

Tibia should be anterior to the femur - in rupture it lies posterior
Direct blow to anterior tibia, (Dashboard / Motorbike) or hyperextension injury
Popliteal knee pain and bruising
Isolated PCL rupture rare (usually with other injury)
Recurrent hyperextension or feeling unstable when going down stairs
In multiligament knee injury

Question 26

What are some complications of knee dislocation?

Hoe should it be managed?

Answer 26

Complete dislocation results in rupture of all four knee ligaments
Popliteal artery injury (tear, intimal tera & thrombosis)
Nerve injury – common peroneal nerve
Compartment syndrome
Intimal tears can occur which later thrombose and therefore regular checks on the circulation of the foot are mandatory.
Should be reduced as an emergency and may require external fixation for temporary stabilization. External fixation takes pressure off of the nerves and vessels.

Question 27

Patellar dislocation
What causes this?
Who is there an increased incidence in?
Complications?

Answer 27

This can either caused by a rapid turn or by a direct blow. 
Increased incidence:
- Females 
- Adolescents
- Ligamentous laxity
- Valgus knee 
- Torsional abnormalities
10% will get a recurrent dislocation 
Can cause chondral or osteochondral injury