Reduction in thequantity of bone or atrophy of skeletal tissue. It occurs in postmenopausal women and elderly men, resulting in bone trabeculae that are scanty and thin. Most fractures sustained by women older than 50 years are secondary to osteoprosis.

A common chronic skeletal disease. It is characterized by bone destruction followed by a reparative process of overproduction of dense yet soft bone that tend to fracture easily. It is most common in men older than age 40. the cause is unknown, but evidence suggests involvement of a viral infection. It can occur in any bone but most commonly affects the pelvis, femur, tibia, skull, vertebrae and clavicle.

Sprain or tear of the ulnar collateral ligament of the thumb near the MCP joint of the hyperextended thumb. The sprain or tear may result from an injury such as falling on an outstretched arm and hand which causes the thumb to be bend back toward the arm.

A common primary malignant bone tumor in children and young adults that arises from bone marrow. Symptoms are similar to symptoms of osteomylitis with low grade fever and pain. Straatified new bone formation results in an onion peel appearance on radiographs. The prognosis is poor by the time Ewing sarcoma is evident on radiographs. 

Slow growing benign carliaginous tumor most often found in small ones of the hands and feet of adolescents and young adults. Generally enchondromas are well defined, radiolucent appearing tumors with a thin cortext that often lead to pathologic fracture with only mnimal trauma.