Table 1

Classification systems—abbreviated from online supplemental material

Based on	Author	G0	G1	GII	GIII	GIV
Clinical Signs	Odonoghue		No appreciable tissue tear	Tissue damage and reduced strength of the muscle tendon unit	Complete tear of the muscle tendon unit and complete loss of function
	Ryan		Tear of a very small number of fibres with Fascia remaining intact	Tear of a higher no of fibres, fascia still remains intact	Greater number of muscle fibres involved. The muscular fascia is at least partially torn	Completed tear of the muscle belly and fascia rupture
	Wise		Min pain to palpation, localised	Substantial TOP, poorly localised, 6–12 mm change in circumference, develops 12–24 hours <50% loss of ROM, pain on contraction, loss of power, disturbed gait	Intractable TOP, diffuse, develops in 1 hour, >50% loss ROM, severe pain on contraction, almost complete loss of power, unable to WB
	Rachun		Localised pain, min swelling, bruising, minor disability	Local pain+TOP, moderate bruising+disability, stretching tearing fibres without disruption	Severe pain+swelling disability, severe haematoma, loss of function, palpable defect
Imaging	Takebyashi		No abnormalities or diffuse bleeding with or without local fibre rupture (less than 5% of the muscle involved)	Focal fibre rupture—more than 5% of the muscle involved, with or without fascial injury	Complete muscle rupture with retraction, fascial injury is present
	Peetrons	lack of US lesion	Minimal elongation with less than 5% of muscle involved—hypoechoic area	Lesions involving from 5% to 50% of the muscle volume or cross-sectional diameter	Complete muscle tears with complete retraction
	Lee		Normal or focal/general areas of increased echogenicity—perifascial fluid	Discontinuity of muscle fibres in echogenic perimysal strae. Hypervascularity around disrupted muscle fibres. Intramuscular fluid collection, partial detachment of adjacent fascia or aponeurosis	Complete myotendinous or tendon-osseous avulsion, complete discontinuity of muscle fibres and associated haematoma. Bell clapper sign
	Chan (ISmULT)		Normal appearance. Focal or general increased echogenicity with no architectural distortion	Discontinuous muscle fibres. Disruption site is hyper-vasculised and altered in echogenicity. No perimysal striation adjacent to the MTJ	Complete discontinuity of muscle fibres. Haematoma and retraction of the muscle ends	Proximal MTJ/muscle proximal/ middle distal/ distal MTJ+intramuscular - myotendionous
	Schneider- Kolsky		<10° ROM deficit	10°–25° ROM deficit	>25% ROM deficit
	Stoller		Hyperintense oedema+/-haemorrhage with preservation of the muscle morphology. Oedema pattern=interstitial hyperintensity and feathery distribution on FSPD or T2FSE+STIR images hyperintense subcutaneous tissue oedema+intermuscular fluid	Hyperintense haemorrhage with tearing of up to 50% of muscle fibres. Interstitial hyperintensity with focal hyperintensity representing haemorrhage in the muscle belly+/-intramuscular fluid. Hyperintense focal defect+partial retraction of muscle fibres. associated myotendinous+tendinous injuries. Hyperintensity+interruption +/- widening of muscle - tendon Unit	Complete tearing+/-muscle retraction. Hyperintense fluid filled gap+hyperintense on FSPDFSE+STIR. Associated adjacent hyperintense interstitial muscle changes
Mixed	Cohen	Point grading score - Age/muscles/location/ cross sectional area/retraction/ longitudinal axis T2 signal length
	Munich	Indirect	Functional muscle disorder (consider neuromeningeal) - negative imaging findings
			Structural muscle injury: Grading on US/MRI classification System
		Direct muscle injury
	BAMIC	Negative imaging findings	<10% cross sectional area	10%–50% cross sectional areas—5–15 cm	>50% cross sectional area >15 xm (tendon >5 cm)	Complete rupture
		A -Myofascial tear (4 grades) incorporating cranio-caudal length and cross-sectional area for grading—small/moderate/extensive/complete
		B - Muscle Tendon Junction tear (4 grades) incorporating cranio-caudal length and cross-sectional area for grading
		C -Intra-tendinous tear (3–4 grades) incorporating cranio-caudal length and cross-sectional area for grading
	Barcelona - (MLG-R) mechanism of injury/location - muscle/grade/previous injury	Negative MRI but clinical suspicion	Hyperintense muscle fibre oedema without intramuscular haemorrhage or architectural distortion (fibre architecture and pennation angle preserved). Oedema pattern: interstitial hyperintensity with feathery distribution on FSPD or T2 FSE? STIR images	Hyperintense muscle fibre and/or peritendon oedema with minor muscle fibre architectural distortion (fibre blurring and/or pennation angle distortion) ± minor intermuscular haemorrhage, but no quantifiable gap between fibres. Oedema pattern, same as for grade 1	Any quantifiable gap between fibres in craniocaudal or axial planes. Hyperintense focal defect with partial retraction of muscle fibres±intermuscular haemorrhage. The gap between fibres at the injury’s maximal area in an axial plane of the affected muscle belly should be documented. The exact % CSA should be documented as a subindex to the grade
		Mechanism of injury	Direct/indirect/stretch or sprint
		Location	Location of lesion—proximal/middle/Distal
		Extracellular matrix	When codifying an intratendon injury or an injury affecting the MTJ or intramuscular tendon showing disruption/retraction or loss of tension exist (gap), a superscript (r) should be added to the grade
Surgical	Wood	Proximal hamstring attachment rupture based on		MTJ versus Tendon injury/avulsion—bony versus tendon/avulsion—partial versus complete/ retraction distance/ sciatic nerve involvement
Surgical	Lampainen	Proximal hamstring attachment rupture based on		No of tendons involved (1–3)/level of athlete(demand)/level of symptoms (pain+function)

BAMIC, British Athletics Muscle Injury Classification; CSA, cross-sectional area; FSE, fast spin echo; FSPD, fat-suppressed proton density; MTJ, musculotendinous junction; ROM, range of motion; STIR, short tau inversion recovery; TOP, tender on palpation; US, ultrasound.