Knee injuries

Question 1

what is the primary function of the Anterior cruciate ligament (ACL)

Answer 1

important stabiliser of the knee, limits anterior translation of the tibia relative to the femur
also contributes to knee rotational stability

Question 2

what is the typical mechanism of injury for an ACL tear?

Answer 2

athlete with a history of twisting the knee whilst weight bearing
majority occur without contact and result from landing from a jump - athlete unable to continue after injury

Question 3

ACL clinical features

Answer 3

rapid joint swelling
significant pain
instability - leg ‘giving way’

Question 4

why is there rapid joint swelling in an ACL tear?

Answer 4

the ACL is highly vascular and damage causes haemarthrosis - apparent within 15-30 mins

Question 5

what are the clinical tests that can identify potential ACL damage?

Answer 5

Lachman Test

Anterior Draw Test

Question 6

what is the Lachman Test?

Answer 6

place knee at 30 degrees flexion with one hand stabilising femur and one pulling tibia forward to assess the amount of anterior movement of tibia compared to femur - examine both knees for comparison

Question 7

what is the anterior draw test?

Answer 7

flex knee to 90 degrees, place thumbs on joint line and index fingers on hamstring tendons posteriorly. apply force anteriorly to demonstrate any tibial excursion - examine both knees for comparison

Question 8

what are dome DDx for ACL tear?

Answer 8

fracture
meniscal tear
collateral ligament tear
quadriceps or patellar ligament tear

Question 9

what investigations are done for a ?ACL tear?

Answer 9

plain film radiograph - AP and lateral - to exclude bony injuries, joint effusion or a lipohaemarthrosis
MRI - gold standard for diagnosis and also pick up associated meniscal tears - 50% ACL tears also have meniscal tear (lateral meniscus most common)

Question 10

management of ACL rupture

Answer 10

immediate - RICE

conservative or surgical - depending on suitability of patient for surgery and current activity levels

Question 11

conservative treatment for ACL rupture

Answer 11

rehab - strength training of quadriceps to stabilise knee

canvas knee splint for comfort

Question 12

surgical repair of an ACL rupture

Answer 12

use of a tendon as an artificial graft, following a period of prehabilitation (physiotherapy input for a few months before surgery)

Question 13

complications of ACL rupture and ACL reconstruction

Answer 13

post-traumatic osteoarthritis

Question 14

what is the main function of the posterior cruciate ligament (PCL)?

Answer 14

primary restraint to posterior tibial translation and prevent hyeprflexion of the knee

Question 15

how to PCL tears occur?

Answer 15

usually occur in high-energy trauma - direct blow to proximal tibia during RTA
less common - low energy trauma where knee is hyper-flexed with a plantar-flexed foot

Question 16

clinical features of a PCL tear

Answer 16

immediate posterior knee pain

instability of the joint and a positive posterior draw test

Question 17

imaging for PCL tear

Answer 17

gold standard is MRI

Question 18

how are PCL tears managed

Answer 18

treated conservatively
knee brace and physiotherapy
may require surgery if patient continues to be symptomatic and has recurrent instability
association with other injuries may require urgent surgical treatment

Question 19

what is the most common injured ligament of the knee?

Answer 19

medial collateral ligament (MCL)

Question 20

what is the main function of the MCL?

Answer 20

act as a valgus stabiliser

Question 21

how is the MCL most commonly injured

Answer 21

when external rotational forces are applied to the lateral knee

Question 22

how are MCL injures graded?

Answer 22

Grade I - mild injury, minimally torn fibres, no loss of MCL integrity
Grade II - moderate injury, incomplete tear and increased laxity of MCL
Grade III - severe injury, complete tear and gross laxity of MCL

Question 23

clinical features of a MCL tear

Answer 23

some patients report hearing a ‘pop’ with immediate medial joint line pain
swelling follows after a few hours (unless haemarthrosis then there will be swelling within minutes)
on examination - increased laxity when testing MCL via valgus stress test
may be unable to weight-bear

Question 24

DDx for MCL tear

Answer 24

fracture
meniscal injury
collateral ligament tears

Question 25

investigations for ?MCL tear

Answer 25

plain radiograph film

gold standard MRI - delineating exact extent and grade of tear

Question 26

management of MCL tear

Answer 26

grade dependent

Question 27

management of MCL tear - grade 1

Answer 27

RICE, analgesia, strength training as tolerated should be incorporated with aim to return to full exercise in ~6 weeks

Question 28

management of MCL tear - grade 2

Answer 28

analgesia with a knee brace and weight-bearing/strength training as tolerated, return to full exercise ~12 weeks

Question 29

management of MCL tear - grade 3

Answer 29

analgesia with knee brace and crutches, associated distal avulsion then surgery is considered
aim to return to full exercise ~12 weeks

Question 30

complications of MCL tear

Answer 30

instability in joint

damage to saphenous nerve

Question 31

where are the menisci located and what is their function?

Answer 31

C-shaped fibrocartilage found in the knee joint - rest on tibial plateau and have 2 main functions 1. shock-absorbers 2. increase articulating surface area

Question 32

differences between the medical and lateral meniscus

Answer 32

medial meniscus - more circular, attached to MCL

lateral meniscus - not attached to LCL

Question 33

what is the most common cause of meniscal tears?

Answer 33

trauma-related injuries - young patient who has twisted their knee whilst it is flexed and weight-bearing
degenerative disease