Penicillin does not reach down into the bones. It is an outdated drug and you really should get yourself better products than that.

For bone infections, you need a stronger drug like cephalexin, ciprofloxacin, clindamycin, etc. to penetrate where you need them to go.

You can get these at http://www.1drugstore-online.com ... however, it takes about 10 days for delivery, so if it is an emergency you need a vet.

As a side note, I had one bitch who I had to put down about 10 years ago, because she actually lost both of her paws. Because of antibiotic mismanagement, the bacteria infecting her bones built resistance to my initial choice of antibiotics, and she developed a rare untreatable twin case of Enterococcus faecalis and Pseudomonas fluorescens infection in both wrists, for which (once the buggers became resistant) there was no treatment. The bacteria actually ate all of the connective tissue surrounding her wrists, despite the fact I had her at the vet for 3 days to undergo treatment. He used a combination of gentamicin and penicillin and still lost her.

In hindsight, the vet should have used a combination of cipro/ampicillin, and he might have been able to save her. Anyway, I digress ...

The point of all this is your antibiotic choices matter, and penicillin is "stone age" antibiotics these days, so it would be better if you learn to keep better, more powerful antibiotics than "feed store penicillin" onhand.

Good luck,

Jack