Originally Posted by TandemGeek

While not wanting to add further confusion to your thought processes, bear in mind that crank shorteners have a potential downside that you need to be mindful of...

Crank shorteners bolt-on to the outside of a standard crankarm and, as a result, increase the overall distance between the pedals and, therefore the cyclists feet, which can create more serious problems for an adult cyclist than cranks that too long.

This particular dimension of bicycle fit is referred to as either "tread" (analogous to the natural distance that exists between a person's feet as they stand or walk) or the "Q-Factor". Children -- for whom crank shorteners are designed -- tend to have very flexible joints which aren't overly sensitive to the increased Q-factor associated with these bolt-on solutions. However, for adults Q-factor can be a major issue even with standard width cranks and the shorter their legs are, the more prounced any ill effects from an increase in Q-factor will be. Therefore, if you go the route of crank shorteners be very sensitive to any feedback from your wife relative to increased hip or knee discomfort.

Just something to keep in mind.