Splines can be useful objects in a drawing, but sometimes you need to edit them with tools that apply to polylines instead. AutoCAD LT 2010 includes a function to enable you to convert a spline into a polyline so you can edit away.
You can find this function in two places: the Edit Spline command and the Edit Polyline command. It doesn't matter which one you choose; Edit Polyline just adds an extra prompt at the beginning to confirm that you want to make the conversion.
When I start the Convert function, I'm prompted for a precision. This number can be anywhere from 0 to 99, with a higher number generating more fit points. As you'll see, low numbers tend to work pretty well.
Pretty close, right? But this polyline only consists of straight-line segments. You can get an even better fit with an even lower precision value if you choose to create a poyline consisting of arc segments instead. This is controlled by the PLINECONVERTMODE variable -- 0 means straight lines and 1 means arcs.
You'll probably want to play around with different combinations of precisions and conversion modes to see what will work best for your own splines.
P.S. I promise there are differences between the last two images and the first! I know it's hard to spot here, but I wanted to show how well the conversion works. Try converting a spline with PLINECONVERTMODE = 0 and a precision of 0 and you'll see the "least accurate" version.