I watched a film some years ago, where a woman I believe walked into a room, it was like a hospital room and someone was under the bed. He then proceeded to slash her tendons at the back of her ankles... etc. something like that anyway and its really getting to me as I can't remember the title. Can anyone help please

Sounds like one of the "Childs Play" movies with Chucky the killer doll

If it was a guy and not a woman, it could have been "Pet Cemetery".
The little boy was run over and then brought back to life by being buried in the Pet Cemetery. He slashes the achilles tendon of the old man across the road by hiding under the bed.