My 14 yo female mix breed is leaking?

Take her to the vet.

Rule out a bladder infection.

More likely she has what is called "spay incontinence".

This is easily treated with an inexpensive medication called Proin (or DES).

I promise that will take care of the problem.

If she is capable of her 3-4 mile walk do NOT by any means cut back. Your excellent exercise program actually helps her arthritis.

Motion helps arhthritis, inactivity makes it worse.

Take her to the vet. It can be something simply treated with antibiotics like a Urinary Track Infection. Leaking is a also a common problem in spayed females, if this is the problem, the vet will give her medication that will stp the leaking. But she definately needs a vet check.

I think the fact that your walking yoru 14 yo female 3 or 4 miles a day is wonderful. As long as she's still game and seem to enjoy the walk, enjoy your time with her. But do be sensative to the days when she may not be able to go as far or be out as long.

I'm not quite sure what could help her keep it in longer, because she's so old. But I do know that once dogs get older, they start having more problems anyways. Just like people do. But I suggest maybe you cut back to only two miles a day for her? Because she's so old it might be really hard on her. =O

You really can't do anything but maybe put down some pee pads. You can always ask your vet.