Earlier I wrote about why I don’t like the “knees out” cue in the squat (parts 1 and 2 here and here). It often comes down to athletes not understanding which muscles to use, and some being too mobile for their own good. They have trouble finding alignment. I also mentioned why not everybody needs the same amount of “mobility work” – working on it can actually predispose some to injury. If you have more passive ROM at a joint than you can actively stabilize, you are essentially asking for injury.  Passive range of motion without active control is a disaster waiting to happen. There is another way you can be hurting yourself or your clients by trying to “mobilize” the joints or muscles. It also has to do with something I mentioned in that same article. It’s something many trainers and mobility devotees don’t think about. It’s your bone structure.