86 Part I Chapter 3 Figure 8 (A) X-ray and (B) volume-rendered SPECT/CT of the left knee after a knee spring system in a patient with medial OA of the knee. SPECT/CT shows slightly increased BTO in the medial compartment consistent with OA and normal BTO at the tibial screws of the knee spring system, but pathologically increased BTO (arrow) and associated lucency (arrowhead) around the femoral screws, indicating loosening. Image courtesy of Prof. Dr W.U. Kampen (Hamburg, Germany). Imaging after knee arthroplasty The optimal imaging strategy in evaluating clinical suspected loosening after TKA is poorly defined judging on internationally accepted multidisciplinary endorsed guidelines. As SPECT/CT is still relatively new in the diagnosis of TKA complications, the evidence is still limited compared to oncological indications of RNI or even total hip arthroplasty (THA), nonetheless it is growing steadily [7, 34, 41, 44, 48, 57]. In persisting pain complaints after several months (6 to 12 or longer), RNI is a proven useful addition to conventional radiography and MRI to reveal the cause of the problem. RNI is less hampered by artefacts frommetallic implants, when compared to both computed tomography (CT) and MRI [45]. Increased BTO in both planar studies and in SPECT/CT is able to visualize biomechanical overloading by depicting areas with increased BTO [34]. Evidence increasingly supports that specific tibial and femoral areas adequately differentiate between physiological biomechanical loading and pathological loading indicating loosening, and bone-SPECT/CT can visualize this with superior localization over planar imaging [1, 7, 34, 44, 48, 56] (Figure 9).