Normal Elbow Carrying Angle Size on Radiography
The carrying angle of the elbow is the angle formed between the long axis of the humerus and the long axis of the ulna when the arm is fully extended and supinated. It reflects the natural lateral deviation of the forearm relative to the upper arm and is important for assessing post-traumatic deformity, congenital anomalies, and surgical outcomes around the elbow joint.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | 154-178¡ |
Clinical Significance
The normal carrying angle, measured on anteroposterior radiography, falls between 154° and 178° when expressed as the humeroulnar angle on the lateral side of the joint. Conventionally, a carrying angle greater than approximately 15° valgus (forearm deviated laterally) is termed cubitus valgus, while an angle less than 0° (forearm deviated medially) is termed cubitus varus. These deformities can result in functional impairment, ulnar nerve traction neuropathy, or cosmetic concern.
Measurement accuracy is critical in the pediatric population, where post-traumatic deformity following supracondylar fractures is a common cause of carrying angle abnormality. A key pitfall is patient positioning: incomplete elbow extension or forearm rotation will artificially alter the measured angle and lead to misdiagnosis.
- Post-traumatic cubitus varus (“gunstock deformity”) following supracondylar fracture
- Cubitus valgus secondary to lateral condyle fracture malunion
- Congenital deformity associated with Turner syndrome or skeletal dysplasia
- Tardy ulnar nerve palsy from chronic cubitus valgus
- Iatrogenic deformity following elbow osteotomy or arthroplasty
Reference: Yochum TR, Rowe LJ. Essentials of Skeletal Radiology. (2005).
Imaging Notes
The carrying angle is assessed on a true anteroposterior (AP) radiograph of the elbow obtained with the arm fully extended, the forearm supinated, and the X-ray beam centered over the joint. The angle is measured between lines drawn along the humeral shaft axis and the ulnar shaft axis; the supplement of this angle (i.e., the lateral opening angle) corresponds to the clinically described carrying angle. Ensuring complete elbow extension is essential, as flexion contracture falsely reduces the apparent angle.
In pediatric patients, growth plates must be identified and excluded from the measurement lines to avoid error. Comparative views of the contralateral elbow are recommended when subtle asymmetry is suspected, as individual anatomic variation can be significant.