DVD ideas for someone with rubbish knees

[Hangingbasket14]

I'm looking for a low impact DVD, I have crap knees which have now flared up due to running. I loved 30 day shred when I have followed it previously but think the jumping/running parts will not be great now. Does anyone know if any of JM's DVD's are more strength/core focused or if there is something better? I'm also considering Davina or Charlotte Crosby so if anyone has any experience of those would be grateful!