The writhe of a knot in the simple cubic lattice (Z(3)) can be computed
as the average linking number of the knot with its pushoffs into four
non-antipodal octants. We use a Monte Carlo algorithm to generate a
sample of lattice knots of a specified knot type, and estimate the
distribution of the writhe as a function of the length of the lattice
knots. If the expected value of the writhe is not zero, then the knot is
chiral. We prove that the writhe is additive under concatenation of
lattice knots and observe that the mean writhe appears to be additive
under the connected sum operation. In addition we observe that the mean
writhe is a linear function of the crossing number in certain knot
families