The Old Knight Shield, like all other Old Knight items, possesses extremely low durability and has a 5% chance of performing an explosion similar to the Wrath of the Gods miracle upon breaking. For a medium shield, it requires rather high Strength, and is very heavy.
Despite these negative attributes, it is an extremely good shield for the point in the game when it is found. It has 100% physical block, decent elemental defenses, and the highest stability for a medium shield in the game.
The user should be mindful of the low durability while using the shield, which may require swapping to a different shield when it gets low, unless the wearer can find an item such as the Bracing Knuckle Ring.