There are endless opportunities to build greater upper body size and strength when recovering from a lower body injury. However, coming up with challenging exercises when weight-bearing lifts are out of the question can be a tall order. And you don't want to have to resort to using all machines and strict isolation exercises.
Here are two great lifts that I've used with injured athletes and lifters that drastically increase shoulder and trunk stability and build bigger shoulders.
The focus in these movements should be on the concentric (lifting) portion of the lift. The dumbbells should be brought down as fast as possible to minimize the eccentric or negative portion, just like you would in a traditional Olympic lift. Without the eccentric, more concentric work can be done.
Although the two lifts are similar, they place a different emphasis on the shoulder girdle and variation between the two is needed when your exercise choice is already limited.
The focus on the snatch should be shrugging and flinging your trunk up to create enough momentum for the dumbbells to travel above your head.