Answer:
The bone disorder that Egil could've probably suffered from is called Paget's disease.
Step-by-step explanation:
Paget's disease is an infrequent chronical bone disorder, in which bone repair occurs rapidly and isolated. This condition may cause a variety of symptons as aching in the spine, head and arms, hips and thighs; leading to health problems as arthritis, heart disease, nervous system issues, hearing loss, vision problems, lose of teeth and a type of cancer named Piaget's sarcoma.
A possible cause for this disorder is a virus called measles virus that occurs during childhood that leads to bone formation alterations.
I hope it helps!