Mean surface roughness (Ra) of patellae following 3 million cycles of wear simulation under mal-aligned conditions Data relates to Table 3 in the manuscript SAMPLE Group 1 Group 2 Group 3 1 3.529 8.7175 20.863 2 1.509 12.965 14.227 3 10.11 13.37 7.595 4 4.97 5 15.643 6 13.193