The Transverse Infrapatellar View: A New Ultrasound Technique to Measure Distal Femoral Cartilage Thickness

To examine the reliability and face validity of ultrasound (US) measurements of distal femoral cartilage thickness (CT) using the infrapatellar view (IPV) with knee extension compared to the traditional suprapatellar view (SPV) with knee hyperflexion in young asymptomatic participants and patients with painful knee osteoarthritis (KOA).

The IPV was obtained in an extended knee position by placing the US transducer on the patellar tendon at a 60° angle tilted toward the distal femoral condyle in 19 young adults (control group) and 70 patients with KOA. The CT was measured at the medial femoral condyle, the intercondylar notch, and the lateral femoral condyle.

The inter-rater intraclass correlation coefficient was higher for IPV-based CT measurement (range, 0.856-0.858) compared to SPV-based CT measurement (range, 0.315-0.523) among the patients with symptomatic KOA. The IPV-based CT differed significantly between the control group and the KOA group at the intercondylar notch (P < .001) and lateral femoral condyle (P = .006). The SPV-based CT differed significantly between the control group and the KOA group only at the lateral femoral condyle region (P = .014).

An infrapatellar US evaluation of the distal femoral CT can be a reliable alternative method to a suprapatellar US evaluation for patients with KOA.