Hello, raydoc, and welcome! I believe achilles tendinitis is a fairly common plie and overwork injury for dancers. Another probably less common one (according to the Harkness Dance injury website) is Anterior Impingement Syndrome: plies are painful due to a bony formation created at the front of the ankle where the shin bone meets the ankle as a result of constant contact and stress. I think that the knee can be injured if proper alignment (knee over 2nd and 3rd toe) is not maintained in plie on a regular basis. Shoulder injuries definitely can be a problem for male dancers as a result of lifting or catching their partners. There is a wonderful website describing dance injuries. It is http://www.med.nyu.edu/hjd/harkness/patients/injuries/
Hope this helps.