Table 2.

Characteristics of patients in the six pain trajectories

	Pain trajectory groups

Characteristic	A (constant mild pain)	C (moderate regression)	E (major regression)	B (severe progression)	D (moderate progression)	F (constant severe)

	n = 186	n = 207	n = 23	n = 35	n = 180	n = 74


Age, years (SD)	56 (0.4)	56 (0.4)	57 (1.1)	55 (0.9)	56 (0.4)	56 (0.5)

Female, %	80	79	83	80	83	85

BMI (SD)^{^a,^b}	25 (0.3)	26 (0.3)	25 (0.8)	26 (0.8)	27 (0.3)	28 (0.6)

Highest achieved education level^{^a,^b}
Primary or secondary school, %	62	77	68	83	83	83
University/college, %	38	23	32	17	17	17

White ethnicity, %	99	98	100	97	97	92

Participants with >1 comorbidity, %^{^a,^b}	32	48	59	57	49	69

NRS in past week (IQR)^{^a,^b}	2.1 (1.0–3.0)	3.4 (2.0–4.0)	5.6 (5.0–7.0)	2.3 (1.0–3.0)	4.5 (4.0–6.0)	6.2 (5.0–7.0)

NRS at moment of questionnaire (IQR)^{^a,^b}	1.7 (1.0–2.0)	2.9 (2.0–4.0)	4.5 (3.0–6.0)	2.1 (1.0–3.0)	4.0 (3.0–5.0)	5.9 (5.0–7.0)

PCI subscales score
Pain transformation (IQR)^{^a,^b}	2.0 (1.5–2.5)	2.1 (1.8–2.5)	2.4 (1.9–3.0)	2.2 (1.5–2.8)	2.3 (1.8–2.8)	2.4 (2.0–2.8)
Distraction (IQR)^{^a,^b}	2.1 (1.6–2.6)	2.2 (1.8–2.6)	2.2 (1.8–2.7)	2.3 (1.6–3.0)	2.3 (1.8–2.6)	2.5 (2.2–2.8)
Reducing demands (IQR)^{^a,^b}	1.9 (1.7–2.3)	2.0 (1.7–2.7)	2.3 (2.0–2.8)	1.9 (1.7–2.0)	2.0 (1.7–2.7)	2.3 (2.0–2.7)
Retreating (IQR)^{^a,^b}	1.5 (1.1–1.9)	1.6 (1.1–1.9)	1.7 (1.1–2.0)	1.5 (1.1–1.9)	1.5 (1.1–1.7)	1.7 (1.3–2.0)
Worrying (IQR)^{^a,^b}	1.4 (1.2–1.7)	1.5 (1.2–1.8)	1.7 (1.4–1.9)	1.6 (1.3–1.9)	1.6 (1.3–1.9)	1.8 (1.4–2.1)
Resting (IQR)^{^a,^b}	1.7 (1.4–2.0)	1.8 (1.4–2.0)	2.0 (1.6–2.3)	1.7 (1.4–1.8)	1.9 (1.6–2.2)	2.1 (1.6–2.6)

WOMAC subscales score
Pain (IQR)^{^a,^b}	15 (5–20)	24 (10–33)	39 (25–55)	19 (10–30)	33 (25–40)	46 (25–60)
Joint stiffness (IQR)^{^a,^b}	24 (13–38)	34 (25–50)	48 (38–63)	24 (13–38)	42 (25–50)	53 (38–63)
Physical function (IQR)^{^a,^b}	14 (6–21)	23 (11–31)	37 (26–49)	16 (6–21)	31 (19–41)	45 (33–58)

Uses pain medication, %	36	38	26	35	39	44

Drinks alcohol, %^{^a}	78	78	91	74	76	63

Smoker or previous smoker, %	11	12	18	14	16	18

Has additional supplements or vitamin intake, %	54	52	46	51	52	57

Pain in the ipsilateral hip, %^{^a,^b}	28	42	74	31	49	51

Morning stiffness knees <30 minutes, %^{^a,^b}	64	67	61	59	76	80

Palpable warmth knee, %	6	6	9	0	6	4

Joint space tenderness knee, %^{^a,^b}	36	51	52	61	70	68

Bony enlargement knee, %	4	4	0	9	6	4

Crepitus during flexion knee, %	53	56	43	51	50	57

Positive re-fill test knee, %	10	9	9	3	9	6

ROM flexion knee, degrees (SD)^{^a}	135 (1)	134 (1)	134 (2)	132 (2)	134 (1)	131 (2)

ROM extension knee, degrees (SD)	3 (0)	3 (0)	3 (0)	3 (0)	3 (0)	3 (0)

Pain during active flexion knee, %^{^a,^b}	32	33	13	32	39	46

Pain during active extension knee, %^{^a}	12	21	18	12	24	29

Pain during active internal rotation ipsilateral hip, %^{^a,^b}	20	28	55	25	39	46

Bouchard swelling digit. 2–5 left or right, %	18	19	17	20	19	24

Heberden node digit. 2–5 left or right, %	48	50	44	31	47	58

Erythrocyte sedimentation rate, mm/hr (SD)^{^a}	9.7 (0.6)	9.4 (0.5)	12.5 (2.3)	9.9 (1.3)	10.9 (0.6)	12.3 (1.1)

Kellgren–Lawrence grade
Distribution, % knees with grade 0/1	57/43	63/37	70/30	56/44	55/45	49/51

Kellgren–Lawrence score ipsilateral hip
Distribution, % hips with grade 0/1	81/19	75/25	70/30	85/15	80/20	79/21

TKA after 5 years follow-up, total	1	2	0	0	8	3

↵a P-value <0.10 from the univariate multinomial regression analyses.
↵b P-value <0.05 from the univariate multinomial regression analyses. BMI = body mass index. IQR = interquartile range. NRS = Numeric Rating Scale for pain. PCI = Pain Coping Inventory. ROM = range of motion. SD = standard deviation. TKA = total knee arthroplasty. WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index.