Quantitative assessment of the knee joint from weight bearing computed tomography

In recent years weight bearing computed tomography (WBCT) has been applied to the knee, delivering 3-D imaging in a physiologically loaded stance. Several quantitative approaches have been used to evaluate this data, with the greatest focus on joint space width (JSW) leading to 3-D JSW being potentially sensitive enough as a useful structural biomarker. Studies of JSW and lower limb alignment have been facilitated by novel technologies and have demonstrated significant differences between the non-weight bearing and weight bearing positions. Further work is needed to look at whole lower limb alignment that involves the interplay of all the joints of the lower limb. Steps are being taken to quantify bone parameters from cone beam technology, while there is an opportunity for contrast arthrography to evaluate articular cartilage and the meniscus in a weight bearing position. The concept of weight bearing imaging has also led to the evolution of different technology solutions, including different types of cone beam set up, upright and supine-loaded multidetector CT techniques. This latter approach has included kinematic CT with gating for acquisitions in different angles of flexion. WBCT has also been combined with MRI for finite element analysis of the meniscus. The increasingly varied applications of WBCT at the knee broadens its definition and hold potential for enhancing our understanding of factors in the onset and progression of osteoarthritis. However a consensus on standardized protocols will be required to facilitate these advances.