A good, or at least adequate, range of spinal extension is critical.
Problems occur when the back support device is used too much.
Any change in the functioning of the knee stemming from the lumbar spine might cause knee pain.
If your feet and ankles stiffen up, the amount of information going to the brain (proprioception) drops dramatically.
The ability to bend forward in a way that recruits the back, not the front, of the body is critical.