Table 1 Differentiation between new, old and recurrent injuries by imaging
Type of injury | Imaging findings | |
|---|---|---|
MR imaging | Ultrasound | |
New (acute) | ||
Grade 1 strain | • Intramuscular ‘feathery’ hyperintensity on fluid-sensitive sequences without muscle fibre disruption | ○ Areas of intramuscular hyperechogenicity and perifascial hypoechogenicity (fluid collection) |
Grade 2 strain | • Hyperintensity (oedema and haemorrhage) intramuscularly or at the MTJ, with extension along the fascial planes between muscle groups | ○ Discontinuity of muscle fibres with hypervascularity around disrupted muscle fibres |
• Irregularity and mild laxity of tendon fibres | ○ Altered echogenicity and loss of perimysial striation adjacent to the MTJ | |
• Haematoma at the MTJ is pathognomonic | ○ Intramuscular fluid collection (hypoechogenicity) with a surrounding hyperechoic halo | |
â—‹ Complete discontinuity of muscle fibers associated with extensive oedema and haematoma, and possible retraction of tendon | ||
Grade 3 strain | • Complete discontinuity of muscle fibres associated with extensive oedema and haematoma, and possible retraction of tendon | ○ Ill-defined area of hyperechogenicity in the muscle, which may cross fascial planes |
Contusion | • T1-weighted and fluid-sensitive sequences may show hypo- to hyperintensity | |
Hematoma | • Acute (<48 h): typically isointense to muscles on T1-weighted images | ○ Appears as a hypoechoic fluid collection and may contain debris |
• Subacute (<30 days): higher signal intensity than muscle on both T1-weighted and fluid-sensitive sequences; variable signal intensities within hematoma | ○ Variable appearance (anechoic, hypoechoic or hyperechoic) within 24 h of injury; appearance changes over the next few days becoming hypoechoic or anechoic | |
Avulsion | • Redundant tendon edge lying within large fluid collection/haematoma | ○ Evaluation is difficult due to the presence of mixed echogenicity haematoma with similar echogenicity to the avulsed tendon |
• A small bony fragment | ||
Old (chronic) | ||
Muscle enlargement or atrophy | • Chronic avulsion has no surrounding fluid and tendon edges may be difficult to define | |
Scar tissue | • Scar tissue appears hypointense on all pulse sequences | ○ Areas of scar tissue have irregular morphological features and display heterogeneous echo texture |
Chronic hematoma | • Dark signal intensity rim seen on all pulse sequences due to hemosiderin (chronic haematoma) | |