Table 2.

Fixed effects for models of change in FM total scores, non-surgical pain, and Symptom Severity Index

Variable	Estimate	s.e.	df	t	P
FM total scores
Intercept	5.997	1.055	173.4	5.685	<0.001
Time	−0.016	0.141	369.5	−0.114	0.910
Time2	1.071	0.159	426.5	6.756	<0.001
Age	−0.011	0.016	147	−0.675	0.501
Surgical cohort (hip)	−0.250	0.317	148	−0.787	0.432
Group (improve)	−0.018	0.514	239	−0.034	0.973
Time×Group	−1.432	0.170	369.1	−8.402	<0.001
Time2×Group	−0.394	0.192	426.1	−2.059	0.040
Non-surgical site pain
Intercept	3.283	0.993	179.1	3.306	0.001
Time	−0.065	0.171	149.3	−0.377	0.706
Time2	0.547	0.159	280.96	3.442	0.001
Age	−0.017	0.014	145.51	−1.177	0.241
Surgical cohort (hip)	0.586	0.296	146.59	1.983	0.049
Group (improve)	−0.195	0.513	225	−0.381	0.704
Time×Group	−0.810	0.207	149.02	−3.908	<0.001
Time2×Group	−0.008	0.192	280.54	−0.044	0.965
Symptom Severity Index
Intercept	3.881	0.818	169.1	4.746	<0.001
Time	0.149	0.101	385.4	1.468	0.143
Time2	0.699	0.114	427.6	6.109	<0.001
Age	−0.004	0.012	146.4	−0.328	0.743
Surgical cohort (hip)	−0.571	0.248	147.3	−2.307	0.022
Group (Improve)	0.284	0.383	234.5	0.743	0.458
Time×Group	−1.035	0.123	385.1	−8.441	<0.001
Time2×Group	−0.369	0.138	427.3	−2.671	0.008

The quadratic time variable was centred. DF: degrees of freedom.