Two Danish researchers have shown that it’s crucial to x-ray suspected osteoarthritis in the knee with the patient in a standing, weight-bearing position rather than a supine, non-weight-bearing position.

Publishing their findings online June 10 in Acta Radiologica, Nikolaj Skou and Niels Egund of the radiology department at Denmark’s Aarhus University describe their project analyzing the cases of 35 women and 23 men (mean age, 56 years; age range, 18 to 87 years) who were referred for routine radiographic examinations of the knees.

Axial radiographs of the patellofemoral joint in both supine non-weight-bearing and standing weight-bearing position in 30° knee flexion were obtained of 111 knees, according to the study abstract.

Measurements performed on the radiographs included patellar tilt, patellar displacement, joint space width and grade of osteoarthritis according to Ahlbäck.

The authors report that, from supine to standing position, the patella moved medially, while medial joint space width and lateral patellar tilt angle decreased (P < 0.0001 for three measured parameters).

Strikingly, in the standing position, medial patellofemoral osteoarthritis was observed in 19 knees compared to just three knees in the supine position.

Meanwhile, 14 knees had lateral patellofemoral osteoarthritis with almost unchanged arthritis grade irrespective of position.

Noting that diagnosis and treatment of osteoarthritis and other patellofemoral disorders are currently often based on images acquired with patients in the supine position, the authors conclude that medial patellofemoral osteoarthritis “can generally not be detected on axial radiographs in supine, non-weight-bearing positions.”

They stress that their work confirms the importance of imaging the patellofemoral joint in standing weight-bearing positions.

The authors previously presented this research to the European Society of Musculoskeletal Radiology. Click here to download their 11-page poster.