Hamstring injuries

Question 1

epidemiology of muscle injuries

Answer 1

10-30% injuries in sport

>90% caused by indirect trauma (overloading) or direct trauma (impact)

Question 2

hamstring injury epidemiology

Answer 2

Commonest muscle injuries in sport
Most common in sprinters then jumpers then combined events then runners
L + R equally injured, upper most commonly injured
Biceps femoris much more commonly affected
M>F
Increasing incidence

Question 3

hamstring anatomy

Answer 3

Question 4

insertion and origin hamstrings

Answer 4

ischial tuberosity

biceps femoris attach at head of fibula
semimembranosis attaches at medial tibial condyle
semitendinosis attaches at anteromedial aspect of the tibia

Question 5

what important structure is present on the lateral side of the semimembranosus?

Answer 5

Sciatic nerve

Need to be cautious when injecting in the upper third of hamstrings

Question 6

Question 7

hamstring functions

Answer 7

• hip extensor
• knee flexor
• external rotator of hip and knee

Question 8

innervation of the bicep femoris

Answer 8

short head = common peroneal nerve
long head = tibial portion of sciatic nerve

NOTE: short head can be absent

Question 9

What is the hypothesised reason for increased incidence of injury in the biceps femoris

Answer 9

long head innervated by tibial portion of sciatic nerve, short head from common peroneal- dual innervation may lead to discordant contraction and injury

Question 10

Define hamstring injury

Answer 10

Acute non contact posterior thigh muscle injuries, with all the athletes reporting an incidence during training or competition, either structural or functional, presented with the SMK triad, leading to time loss of > 1 day

Question 11

British Athletics classification of muscle injury

Answer 11

0-5 based on extent, then based on site:

a = myofascial
b = muscular/musculotendinous
c = intratendinous

Extent is determined by MRI

Question 12

What does the following MRI show?

Answer 12

Axial T2-weighted image showing interfascicular and myofascial oedema, reflecting grade 1 muscle injury

involves long and short head of biceps femoris

Question 13

What type of muscle injury is shown in the following MRI

Answer 13

Grade 2a injury (small extent, myofascial)

Lateral aspect of long head of biceps femoris

Question 14

What type of muscle injury is shown in the following MRI

Answer 14

Grade 2b injury (small extent, musculotendinous)

Long head of biceps femoris

Question 15

What type of muscle injury is shown in the following MRI

Answer 15

Grade 2c injury (medium extent, tendinous)

To long head of biceps femoris

Question 16

Which imaging modality is used as gold standard in suspected hamstring rupture and what are the issues with this form of imaging?

Answer 16

T2 weighted MRI
In severe injuries where rupture is suspected, determines extent and location of rupture, as well as extent of tendon retraction (if complete)
This determines whether surgery is needed

However, 70% of symptomatic hamstring injuries show no change in MRI

Question 17

How can USS be used to classify muscle injuries?

Answer 17

Grade 0 = normal
Grade 1 = subtle findings- ill defined hyper/hypoechoic intramuscular lesions/swollen aponeurosis
Grade 2 = partial muscle tear- haematoma formation
Grade 3 = complete tear, haematoma formation

Question 18

Describe the anatomical classification of muscle tears

Answer 18

1st grade = mild = small number of injured fibres
2nd grade = moderate = incomplete tear
3rd grade = severe = complete tear

Question 19

What factors play a significant role in prognosis of hamstring injury?

Answer 19

WORSE PROGNOSIS

• time to walk pain free >24h
• previous hamstring injury

BETTER PROGNOSIS

• first injury
• non contact
• contracting type injury
• biceps femoris
• grade 1 with no imaging findings
• FASH score

Question 20

How can hamstring injury be classified according to time to return to play?

Answer 20

minimal (1-3 days absence), mild (4-7 days absence), moderate (8-28 days), severe (>28 days)

Question 21

What is the MSK injury triad

Answer 21

1. Tenderness to palpation
2. Pain with resisted movement
3. Pain with passive stretching

Question 22

2 main mechanisms of hamstring injury in non-contact hamstring injuries

Answer 22

contractive type injuries:
- during high speed running (80%) mainly located in head of biceps femoris and involves proximal muscle-tendon junction

Stretching-type injuries:

• extensive lengthening (20%) eg high kicking, sliding tackle etc
• located close to ischial tiberosity and typically involves tendon tissue of semimembranosus

Question 23

Which hamstring injuries require surgical intervention?

Answer 23

severe injuries eg complete rupture
either at insertion or origin (avulsion)
results from extreme hip flexion with knee fully extended

Question 24

Ddx hamstring injury

Answer 24

referred pain to posterior thigh from another source

• gradual instead of sudden
• tightness/cramping
• able to walk
• no haematoma
• no pain on palpation
• no decrease in strength

Question 25

For initial presentation of a hamstring injury, what steps are followed from acute injury –> recovery?

Answer 25

1) Hx, examination
2) 48h POLICE
3) re-evaluate aROM, functional assessment, imaging
4) find degree of severity
5) plan Tx- rehab, surgery, return to play (RTP)

Question 26

Summarise all the methods of hamstring classification

Answer 26

Question 27

classificaiton hamstring re-injury

Answer 27

injury at same site of original injury
early within 2 months
late 3-12 months

accumulation of scar tissue leads to high rates of recurrence