Differentiating Elbow Arthritis from Olecranon Fracture on X-ray
Elbow arthritis and olecranon fractures have completely distinct radiographic appearances: arthritis shows osteophytes, joint space narrowing, and subchondral sclerosis in a chronic pattern, while olecranon fractures demonstrate a discrete cortical break with sharp fracture lines.
Key Radiographic Features of Elbow Arthritis
Osteophyte formation is the hallmark finding, present in 96% of olecranon arthritis cases, 90% at the coronoid process, and 86% at the radial head 1. These bony outgrowths represent chronic degenerative changes rather than acute trauma.
Primary Arthritis Findings:
- Joint space narrowing occurs predominantly at the radiocapitellar joint (58%) rather than the ulnotrochlear joint (16%), distinguishing pathologic arthritis from normal aging 1
- Subchondral sclerosis appears as increased bone density beneath the articular surface 2
- Filled coronoid and radial fossae are present in 64% of arthritic elbows, representing chronic osteophyte formation 1
- Thickening of the olecranon fossa membrane occurs in 68% of cases 1
- Loose bodies may be present as secondary features of chronic degeneration 3
Distribution Pattern:
The American College of Radiology emphasizes that radiographs should be obtained in standard AP and lateral views to identify the characteristic distribution of degenerative changes 3. Comparison with the contralateral asymptomatic elbow is useful when findings are subtle 3, 4.
Key Radiographic Features of Olecranon Fractures
Olecranon fractures demonstrate a discrete cortical break with sharp, well-defined fracture lines through the olecranon process 5. These are acute traumatic injuries, not chronic degenerative processes.
Primary Fracture Findings:
- Cortical disruption with a visible fracture line traversing the olecranon
- Displacement of fracture fragments (Mayo type 2 is most common) 5
- Sharp, irregular bone edges at the fracture site, contrasting with the smooth, rounded contours of osteophytes
- Absence of chronic degenerative features such as osteophytes, subchondral sclerosis, or joint space narrowing in the acute setting
- Possible joint effusion or soft tissue swelling in acute trauma
Clinical Context:
Olecranon fractures account for 10% of all elbow fractures and typically result from low-energy trauma 5. The history of acute injury versus chronic pain progression is critical for interpretation.
Advanced Imaging When Radiographs Are Equivocal
CT elbow is superior for identifying complex fracture patterns, fragment displacement, and distinguishing subtle fractures from chronic degenerative changes 3. CT has 93% sensitivity for detecting loose bodies and provides excellent bone detail 3.
MRI is indicated when occult fractures are suspected despite normal radiographs, as it demonstrates bone marrow edema and periosteal fluid at fracture sites 3. However, MRI is less sensitive than radiographs for detecting heterotopic ossification and calcifications 3.
Common Pitfalls to Avoid
- Do not mistake large olecranon osteophytes for displaced fracture fragments—osteophytes have smooth, corticated margins while fractures show sharp, irregular edges 1
- Avoid over-relying on a single radiographic view—obtain both AP and lateral projections to fully characterize the pathology 3
- Do not order MRI before plain radiographs, as this wastes resources and MRI is less sensitive for calcifications and ossifications 4
- Consider that posteromedial olecranon impingement in throwing athletes can mimic arthritis, but CT is superior to MRI for detecting joint space narrowing and subluxation in this specific context 2