Periostitis

Inflammation of the periosteum, a dense membrane composed of fibrous connective tissue that closely wraps (invests) all bone, except the bone of articulating surfaces in joints which are covered by synovial membranes.

The word 'periotitis' may seem like Greek to you.

'Peri-' is a prefix borrowed from the Greek meaning 'around or about', '- osteal' comes from the Greek 'osteon' meaning 'bone', and the Greek suffix 'itis' meant 'disease' and now, more narrowly, means 'inflammation.' So periostitis literally is inflammation around the bone