Miter joints are not the strongest joints, but when you add a spline that all changes

A splined miter joint is probably the strongest miter joint you can have.

When I build mitered boxes so no end grain is showing I hide the spline inside the joint running parallel with the length of the joint.

For picture frames that doesn't work. The spline technique in this video is a great way to strengthen the joint and at the same time the splines add a decorative feature to the picture frame.

Here's how it is done.

Here's another decorative splined miter alternative.  –Click Here —