Inge’s reign fell within the start of the period known in Norwegian history as the civil war era, and he was never the sole ruler of the country.
Their respective guardians joined forces against Sigurd Slembe and his ally, the former king Magnus the Blind.
According to the sagas Morkinskinna and Heimskringla, Inge’s infirmity stemmed from having been carried into battle by one of his guardians during a battle in 1137: “...his back was knotted into a hump, and the one foot was shorter than the other; and he was besides so infirm that he could scarcely walk as long as he lived.”s:Heimskringla/Saga of Sigurd, Inge, and Eystein, the Sons of Harald#Of Sigurd Slembidjakn.
The Danish chronicler Saxo Grammaticus offers the alternative explanation that he became a hunchback after having been dropped on the floor by a maid during infancy.
The division of the kingdom does not seem to have been territorial, all brothers seem to have held equal regal status over all parts of the country.
According to the sagas, Eystein and Sigurd had plotted to strip Inge of his royal title and divide his share of the kingdom between them.
Heimskringla notes that Inge was popular among the “chieftains” – the lendmenn – because he allowed them a great say in the running of the kingdom.
The main sources to Inge’s reign are the kings’ sagas Heimskringla, Fagrskinna, Morkinskinna and Ágrip.
The three former base at least part of their account on the older saga Hryggjarstykki, which was written some time between 1150 and 1170, and was thus a near-contemporary source.