A comparative assessment of alignment angle of the knee by radiographic and physical examination methods
Article first published online: 2 JUN 2005
Copyright © 2005 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 52, Issue 6, pages 1730–1735, June 2005
How to Cite
Kraus, V. B., Vail, T. P., Worrell, T. and McDaniel, G. (2005), A comparative assessment of alignment angle of the knee by radiographic and physical examination methods. Arthritis & Rheumatism, 52: 1730–1735. doi: 10.1002/art.21100
- Issue published online: 2 JUN 2005
- Article first published online: 2 JUN 2005
- Manuscript Accepted: 9 MAR 2005
- Manuscript Received: 27 OCT 2004
- National Institute of Arthritis and Musculoskeletal and Skin Diseases. Grant Number: R01-AR-48769
- National Center for Research Resources. Grant Number: M01-RR-30
To compare the knee-alignment angle from a full-limb radiograph (mechanical axis) with the anatomic-axis angle as measured by physical examination using a goniometer and by 2 other radiographic methods.
The knee-alignment angle was measured in 114 knees of 57 subjects who had radiographic osteoarthritis (OA), with a Kellgren/Lawrence grade of ≥1 in at least one knee. The mechanical axis was defined as the angle formed by the intersection of 2 lines, one from the center of the head of the femur to the center of the tibial spines, and a second from the center of the talus to the center of the tibial spines. The anatomic axis was defined as the angle formed by 2 lines, each originating from a point bisecting the femur and tibia and converging at the center of the tibial spine tips. The anatomic-axis angle was measured by 3 methods: 1) physical examination using a goniometer, 2) a posteroanterior (PA) fixed-flexion knee radiograph (anatomicPA axis), and 3) an anteroposterior (AP) full-limb radiograph (anatomicAP axis).
Significant correlations were found between the mechanical-axis angle and the anatomic-axis angle measured by each of the 3 methods: by goniometer (r = 0.70, P < 0.0001), by anatomicPA axis (r = 0.75, P < 0.0001), and by anatomicAP axis (r = 0.65, P < 0.0001). The anatomic axis was offset a mean 4.21° valgus from the mechanical axis (3.5° in women, 6.4° in men), which was consistent across all methods.
Knee alignment assessed clinically by goniometer or measured on a knee radiograph is correlated with the angle measured on the more cumbersome and costly full-limb radiograph. These alternative measures have the potential to provide useful information regarding the risk of progression of knee OA when a full-limb radiograph is not available.