Knuckle boom crane

A knuckle boom crane, also knowns as an articulating boom crane, is a kind of standard crane whose boom articulates at a 'knuckle', letting it fold back like a finger. This provides a compact size for storage and manoeuvring. Other knuckle booms are typical in North American excavators, which usually have two articulations like an index finger. Most often seen are hydraulically-actuated knuckle booms.