The classification of radial head fractures is based on the

• degree of displacement
• intra-articular involvement

as follows

• Mason type 1 - non-displaced to minimally displaced fracture (<2mm)
• Mason type 2 - intra-articular fracture with displacement >2 mm or angulation
• Mason type 3 - comminuted intra-articular fracture with displacement 

Posttraumatic instability of the sternoclavicular joint is a result of injury to the joint capsule, the sternoclavicular or costoclavicular ligament.

Mayfield et al. described in 1980 the following four stages of progressive carpal instability.

Thompson-Epstein classification describes five types of posterior hip dislocation defined by associated acetabular fracture or fracture of the femoral head as depicted on plain radiographs. In general, there are three types of dislocations in the hip joint:

• posterior: the femoral head is dislocated posteriorly, most commont type
• anterior: the femoral head is dislocated anteriorly
• central: impact of the femoral through the acetabular floor into the pelvis

Rockwood classification divides dislocations in AC joint into six grades. It is an extension of the previous classification by Tossy et al. Normal width of AC joint is considered 1-3mm, widened AC joint has >7mm in men or >6mm in women.

Tossy classification divides dislocations in AC joint into three grades. It was later extended by Rockwood et al. by another three types. Normal width of AC joint is considered 1-3mm, widened AC joint has >7mm in men or >6mm in women.

Complete atlanto-occipital dislocation (AOD) can be divided into three distinct types.

Kerley lines are named after Peter J. Kerley, a British radiologist, who identified types of septal lines on chest radiographs in patients with congestive heart failure.

Neer classification divides lesions of the rotator cuff into three stages that typically succeed in this order during one's life.

Grading of joint osteoarthritis by Ahlbäck uses plain postero-anterior weight-bearing radiographs to assess the extent of degenerative disease as joint space narrowing and bone attrition.