There have been many different devices designed to assist lifting a heavy leg into bed. Therapostures attempt is one of the best you will come across.

If your patient can sit on the edge of the bed, then this is as much effort as they need to put in. With the press of just one button, the Theracare leg lifter will do the rest.

As the leg lifter performs its operation, the legs are not only lifted but are then, unlike many other leg raisers which just lift to the side, the legs are rotated and gently placed on the bed. To aid balance there is an easy to hold handle. The unit is secured firmly to the bed to ensure a firm and stable transfer.

http://www.theraposture.co.uk/leglifterimages/Leg%20Li fter%20Bro.pdf