Table 2.

Association of change in serum cytokine and neurotransmitter levels from baseline to 2-months with pain responder status on WOMAC pain at 2-month post-injection in painful TKA

	WOMAC Pain Responder*	N	Mean Change (FU-Baseline)	Std. Deviation	Std. Error Mean	P-value
Interleukin (IL)-7	No	23	0.084	0.91	0.19	0.01
	Yes	12	1.07	1.17	0.34
IL-10	No	23	8.51	20.90	4.36	0.01
	Yes	12	27.72	21.56	6.22
IL-12 p70	No	23	3.36	8.17	1.70	0.004
	Yes	12	12.91	9.60	2.77
Eotaxin	No	23	−2.03	13.92	2.90	0.046
	Yes	12	7.85	12.28	3.54
Interferon gamma (IFN-γ)	No	23	−1.24	23.18	4.83	0.03
	Yes	12	15.61	13.35	3.85
Tumor necrosis factor-alpha (TNF-α)	No	23	4.46	21.32	4.44	0.03
	Yes	12	22.22	24.65	7.12
IL-4	No	23	−0.02	0.16	0.03	0.12
	Yes	12	0.06	0.12	0.03
IL-6	No	23	−15.90	275.66	57.48	0.09
	Yes	12	137.35	182.09	52.56
IL-13	No	23	4.90	13.25	2.76	0.15
	Yes	12	12.18	14.87	4.29
IL-15	No	23	0.31	11.87	2.47	0.09
	Yes	12	7.36	10.52	3.038
Macrophage Inflammatory Protein-1 beta (mip1b)	No	23	5.55	91.43	19.06	0.16
	Yes	12	53.35	96.39	27.82
Substance P	No	14	0.08	1.11	0.298	0.32
	Yes	5	−0.46	0.61	0.273

Only those associations that either had a significant p-value or a p-value <0.33 are listed; The levels of other cytokine did not differ significantly between pain responders and pain non-responders (IL-1 beta, IL-1 alpha, IL-2, IL-5, IL-8, IL-9, IL-17, Basic FGF, G-CSF, GM-CSF, IP-10, MCP-1, MIP-1 alpha, PDGF, RANTES, and VEGF). Significant p-values <0.05 are in bold

Positive changes mean that at the 2-month follow-up time, the levels were higher than the baseline and a negative sign means follow-up levels were lower

WOMAC Pain Responder* is defined as reduction in WOMAC pain subscale of 20 or more 0–100 scale