Is there more than one way to pronounce "knee" in Chinese? My daughter's preschool has a Mandarin language immersion program and the teacher (from Fuzhou, Fujian province) seems to pronounce "knee" (膝盖) as qīgài instead of xīgài. 

Is qīgài a correct alternative pronunciation, or is her own dialect incorrectly corrupting her Mandarin pronunciation? If the latter, what other pronunciation errors is she likely to make?
It is a non-standard pronunciation, but it is reasonably common. It is not in any way associated with the Fuzhou dialect specifically — even some northerners say qigai. Here's an interesting blog post and discussion about the free variation of the pronunciations of knee.