Table 3.

Ceiling and floor effects within 12 months after total knee arthroplasty

	FJS, % (n)	WOMAC, % (n)	P value
Ceiling
3 months (n = 84)
Maximum	1.2 (1)	0 (0)	1
Highest 10%	2.4 (2)	7.1 (6)	1
Highest 15%	7.1 (6)	11.9 (10)	0.148
6 months (n = 56)
Maximum	5.4 (3)	1.8 (1)	0.045*
Highest 10%	10.7 (6)	16.1 (9)	0.046*
Highest 15%	19.6 (11)	32.1 (18)	0.027*
12 months (n = 23)
Maximum	8.7 (2)	8.7 (2)	0.170
Highest 10%	13.0 (3)	30.4 (7)	0.209
Highest 15%	26.1 (6)	39.1 (9)	0.162
Total (n = 163)
Maximum	3.1 (5)	1.8 (3)	0.003*
Highest 10%	6.7 (11)	13.5 (22)	0.001*
Highest 15%	14.1 (23)	22.7 (37)	<0.001*
Floor
3 months (n = 84)
Minimum	6.0 (5)	0 (0)	0.061
Lowest 10%	16.7 (14)	0 (0)	<0.001*
Lowest 15%	21.4 (18)	0 (0)	<0.001*
6 months (n = 56)
Minimum	5.4 (3)	0 (0)	0.248
Lowest 10%	10.7 (6)	0 (0)	0.030*
Lowest 15%	10.7 (6)	0 (0)	0.030*
12 months (n = 23)
Minimum	0 (0)	0 (0)	1.000
Lowest 10%	4.3 (1)	0 (0)	1.000
Lowest 15%	13.0 (3)	0 (0)	0.248
Total (n = 163)
Minimum	4.9 (8)	0 (0)	0.007*
Lowest 10%	12.9 (21)	0 (0)	<0.001*
Lowest 15%	16.6 (27)	0 (0)	<0.001*

Abbreviations: FJS Forgotten Joint Score, WOMAC Western Ontario and McMaster Universities Arthritis Index

* P <0.05