Here is an interesting photo (if you are a fellow hoof-anorak!). Its a photo of a horse who has been barefoot for over 2 years and has rock-crunching hooves. However, about 6 months ago he strained a check ligament and was on box rest for 4 months. Its been 2 months now that he has been out and able to move around.
If you look at his hoof growth, you can see that while he was on box rest his hooves shut down, but once he was able to move again, a much healthier, better connected hoof capsule started to grow back.
The angle of change is almost identical to the angle you see in a hoof when shoes have come off - like Blue's photos here - and its a sign of increased circulation and stimulation to the hoof.