Table 3.

Defining and of grading of OA features using USI.

Sonographic feature	Definition	Grading system
		Semiquantitative	Dichotomous (present or absent)	Continuous (mm)
Osteophytes	Cortical protrusion >1 ​mm at the end of the normal bone contour or at the margin of the joint	[38,42,44,49,54,55,60,63,65]	[37,40,51,53,56,57,60,62]	NR
	[38,44,51,53,[55], [56], [57],[60], [61], [62],66]
Erosions	Irregularity of the hyperechoic cortical bone, evident in two perpendicular planes	NR	[37,40,56,57]	NR
	[38,40,50,57]
Articular cartilage damage	Loss of the normal sharpness of cartilage interfaces, irregularities/thinning of the margins and/or increased echogenicity of the cartilage	[44]	[53,58,65]	[59]
	[53,58,65]
Synovitis	Distension of the joint capsule ≥1.5 ​mm in its anteroposterior diameter with compressible material	[24,[36], [37], [38],40,45,48,60,61,63]	[41,53,56,57,59,60]	NR
	[45,53]
	A composite of effusion and synovial thickening
	[24,38,48,[59], [60], [61]]
Synovial hypertrophy	Abnormal hypoechoic intraarticular tissue or thickening of the synovial membrane that is non-displaceable and poorly compressible and is often associated with increased vascularity	[39,43,[46], [47], [48], [49],52,54]	[40,50,65,66]	NR
	[38,48,52]
Joint effusion	Abnormal hypoechoic or anechoic intra-articular material that is displaceable and compressible but does not exhibit power Doppler signal	[24,39,[47], [48], [49],52,54,64]	[40,50,56,57,65,66]	NR
	[38,48,50,54,56,57,64,66]
Power Doppler activity	A pulsating colour spot found within the synovial structure, which represented presence of vascularisation	[24,36,37,39,40,[43], [44], [45],[47], [48], [49],52,54,[61], [62], [63], [64], [65]]	[36,38,50,53,57,59,66]	NR
	[24,38,40,45,48,50,52,53,61,62,64]
Joint space narrowing	Decrease in the space between the cortical margins	NR	[53,61,62]	NR
	[53,61,62]
Tenosynovitis	A hypoechoic rim around tendon with or without PD signal	NR	[56,57]	NR
	[56,57].

NR, Not reported.