Changes

***Physiological loss of skeletal mass with age

***Physiological loss of skeletal mass with age

***May be excessive in some individuals

***May be excessive in some individuals

***Histologically - dead [[Bones - normal#Normal stucture|osteocytes and empty lacunea]]

***Histologically - dead [[Bones - Anatomy & Physiology|osteocytes and empty lacunea]]

**Physical inactivity (disuse) - muscular inactivity and reduced weight bearing, e.g. during limb casting

**Physical inactivity (disuse) - muscular inactivity and reduced weight bearing, e.g. during limb casting

**Glucocorticoids

**Glucocorticoids

***Scattered cancellous and endosteal bone

***Scattered cancellous and endosteal bone

*Histologically:

*Histologically:

**Empty [[Bones - normal#Normal structure|lacunae or contain dead osteocytes]]

**Empty [[Bones - Anatomy & Physiology|lacunae or contain dead osteocytes]]

**Matrix remains mineralised

**Matrix remains mineralised

*Necrotic bone is slowly resorbed, sequstered or covered by new woven bone  

*Necrotic bone is slowly resorbed, sequstered or covered by new woven bone  

*'''Simple cysts'''

*'''Simple cysts'''

**May contain clear colourless fluid, or serosanguinous

**May contain clear colourless fluid, or serosanguinous

**Wall of dense fibrous tissue, [[Bones - normal#Bone organisation|woven or lamellar bone]]

**Wall of dense fibrous tissue, [[Bones - Anatomy & Physiology|woven or lamellar bone]]

*'''Aneurysmal bone cysts'''

*'''Aneurysmal bone cysts'''

**Expansie lesions

**Expansie lesions