Enthesis

Like arthritis, peripheral enthesitis occurs predominantly in the lower extremities, particularly in the foot, at single sites at onset, and then at several entheses throughout the course of the disease.

Functional entheses occur where tendinous and ligamentous structures, while not actually attaching to bone, are adjacent and in a close relationship to the underlying bone.

Inflammation of the enthesis, when associated with arthritis in children, is called the syndrome of seronegative enthesopathy associated with arthritis (SEA). The entheses most commonly involved in children are the plantar aponeurosis, calcaneal enthesis, and distal and proximal patellar ligament insertions.