Table 4.

Strata of weakness^a by clinical group

	PM (n = 65) (percentage of subjects)				DM (n = 50) (percentage of subjects)				JDM (n = 57) (percentage of subjects)
Muscle groups	None	Mild	Moderate	Severe	None	Mild	Moderate	Severe	None	Mild	Moderate	Severe
Neck flexors	11	46	35	8	8	52	34	6	14	37	44	5
Neck extensors	51	35	12	2	42	44	12	2	44	47	9	0
Shoulder elevators	71	20	8	2	82	16	0	2	67	28	5	0
Shoulder abductors	15	55	17	12	16	62	22	0	30	47	21	2
Elbow flexors	42	45	14	0	50	34	16	0	40	47	12	0
Wrist flexorsb	52	42	6	0	30	52	16	2	46	47	5	2
Wrist extensors	46	48	6	0	26	68	6	0	44	47	9	0
Hip flexorsc	2	25	40	34	4	34	36	26	14	51	30	5
Hip extensorsc	2	23	29	46	2	26	44	28	25	51	16	9
Hip abductorsc	9	26	40	25	14	56	22	8	28	49	18	5
Knee extensorsc	25	52	18	5	40	52	8	0	63	28	9	0
Ankle dorsiflexors	48	48	2	3	58	40	2	0	58	40	2	0
Ankle plantar flexorsb	45	45	9	2	66	34	0	0	61	32	7	0

^aStrata of weakness are based on the MMT grading criteria: no detectable weakness = 10 out of 10, ability to move against gravity into the testing position and hold against maximal manual resistance; mild weakness = 7–9 out of 10, ability to move against gravity into the testing position and hold against varying degrees of submaximal manual resistance; moderate weakness = 4–6 out of 10, inability to sustain the testing position against gravity (4), inability to withstand minimal manual resistance in the testing position (5) or ability to withstand minimal manual resistance (6); severe weakness = 0–3 out of 10, inability to move limb beyond partial range of motion (<50% of partial range of motion) against gravity. ^bDistribution among clinical groups differs, P < 0.05, Kruskal–Wallis non-parametric rank test for contingency table data. ^cDistribution among clinical groups differs, P < 0.001, Kruskal–Wallis non-parametric rank test for contingency table data. (Values in rows may not equal 100% due to rounding; unilateral data were symmetrical, therefore only values from right side are included.)