APPENDIX 1.

Results stratified by age (at median), sex, and obesity status.

		Age (> median)			Age (< median)			Female			Male			Obese			Not Obese
		Sn	Sp	LR+	Sn	Sp	LR+	Sn	Sp	LR+	Sn	Sp	LR+	Sn	Sp	LR+	Sn	Sp	LR+
AKP	Any	63	55	1.4	57	51	1.2	64	48	1.2	47	61	1.2	57	58	1.4	64	45	1.2
AKP	Isolated	28	84	1.8	26	79	1.2	29	81	1.5	21	82	1.2	28	84	1.8	27	77	1.2
Max pain with stairs (up or down)	(≥ min)	78	38	1.3	68	28	0.9	73	27	1.0	74	42	1.3	69	38	1.1	80	26	1.1
Max pain with stairs (up or down)	(≥ mod)	43	71	1.5	36	68	1.1	42	68	1.3	34	73	1.3	33	74	1.3	48	63	1.3
Pain with up stairs	(≥ min)	77	38	1.2	65	29	0.9	71	28	1.0	74	42	1.3	66	38	1.1	79	27	1.1
Pain with up stairs	(≥ mod)	35	76	1.5	34	72	1.2	36	73	1.3	32	75	1.3	27	77	1.2	45	69	1.5
Pain with down stairs	(≥ min)	73	46	1.4	54	34	0.8	66	35	1.0	55	48	1.1	60	46	1.1	68	30	1.0
Pain with down stairs	(≥ mod)	36	80	1.8	26	81	1.4	33	79	1.6	28	82	1.6	28	85	1.9	36	73	1.3
Absence of pain walking on level ground	(≥ min)	56	39	0.9	60	48	1.2	58	46	1.1	60	40	1.0	62	40	1.0	53	50	1.1
Absence of pain walking on level ground	(≥ mod)	93	14	1.1	93	12	1.2	93	17	1.1	94	7	1.0	94	10	1.0	92	17	1.1
Any AKP + max pain with stairs	(≥ min)	56	67	1.7	42	62	1.1	53	58	1.3	38	74	1.5	45	70	1.5	54	56	1.2
Any AKP + max pain with stairs	(≥ mod)	34	83	2.0	23	82	1.1	33	81	1.7	17	85	1.1	25	87	1.9	34	76	1.4
Any AKP + absence of pain walking on level ground	(≥ min)	30	77	1.3	29	75	1.3	30	73	1.1	28	80	1.4	31	77	1.3	28	73	1.0
Any AKP + absence of pain walking on level ground	(≥ mod)	59	65	1.7	53	55	1.2	59	58	1.4	47	64	1.3	54	63	1.5	59	56	1.3
Isolated AKP + max pain with stairs	(≥ min)	25	93	3.6	14	86	1.0	21	88	1.8	17	93	2.4	19	92	2.4	21	86	1.5
Isolated AKP + max pain with stairs	(≥ mod)	12	99	12.0	7	95	1.4	11	96	2.8	4	98	2.0	7	98	3.5	12	94	2.0
Isolated AKP + Absence of pain walking on level ground	(≥ min)	19	88	1.6	21	85	1.4	21	86	1.5	17	87	1.3	21	88	1.8	18	85	1.2
Isolated AKP + Absence of pain walking on level ground	(≥ mod)	26	85	1.7	26	80	1.3	28	82	1.6	21	82	1.2	27	85	1.8	26	78	1.2

Sn: Sensitivity; Sp: Specificity; LR+: Positive likelihood ratio; AKP: anterior knee pain; max: maximum; min: minimal; mod: moderate.