Table 2.

Summary of qualitative grading of histologically stained micrographs^*

Parameter, age	WT mice	Prg4−/− mice
Articular cartilage structure
2 weeks	0.64 ± 0.63	1.75 ± 1.27†
4 weeks	0.46 ± 0.34	1.75 ± 0.87†
10 weeks	0.46 ± 0.27	1.71 ± 0.34†
16 weeks	0.36 ± 0.32	1.75 ± 0.74†
Surface layer morphology
2 weeks	0.07 ± 0.12	1.71 ± 0.62†
4 weeks	0.39 ± 0.32	2.04 ± 0.53†
10 weeks	0.14 ± 0.28	1.93 ± 0.55†
16 weeks	0.18 ± 0.19	1.68 ± 0.43†
Pericellular loss of Safranin O staining
2 weeks	0.29 ± 0.62	0 ± 0
4 weeks	0.62 ± 0.59	1.52 ± 1.82
10 weeks	2 ± 0.69	2.62 ± 1.27
16 weeks	1.1 ± 1.44	3.05 ± 0.68†

^*Values are the mean ± SD. For each age group, femoral heads from 7 mice of each genotype were examined.

^†P < 0.05 versus wild-type (WT) mice.