83 SPECT/CT in the post-operative painful knee surgery such as position of bone tunnels or fixation material [41]. Additionally, stress radiographs allow assessment of ligament integrity. In patients with an unhappy total knee arthroplasty, a Kanekasu’s view (the patient sitting on a frame with the lower legs hanging down and bent 90°) allows assessment of flexion instability as well as rotation of the femoral TKA component. Magnetic resonance imaging (MRI) is an excellent imagingmodality in knees without any metallic devices implanted. It allows assessment of the menisci, ligaments and cartilage and displays bone marrow edema [41]. When compared to bone-SPECT/ CT, MRI is more expensive and both acquisition and reconstruction of specific MRI sequences are more time-consuming. Currently the main limitation of MRI is the fact that it is hampered by metallic artefacts. However, metal artefact reduction sequences (MARS) are improving rapidly and evidence emerges that for some questions MRI is feasible even after TKA [61]. Still, even with the most advanced MARS-protocols, especially Cobalt/Chrome/Molybdenum alloy femoral components will continue to produce artifacts, leading to reduced interobserver agreement in for example determining component malalignment [61]. In comparison to patients with hip arthroplasty, MRI is still clearly less frequently used for patients after TKA in clinical routine. While conventional radiography andMRI are first-line imagingmodalities in particular for the initial acute setting, radionuclide imaging (RNI) is considered as an important complementary second line imaging modality in a wide range of knee problems [7, 41, 44, 45]. A proposed diagnostic algorithm for patients with clinical symptoms is summarized in Figure 6, based on the algorithmas described by Hirschmann, et al [1]. Imaging after knee joint preserving surgery MRI is the reference standard in the evaluation of an ACL reconstruction with adequate visualization of graft tear and arthrofibrosis, usually combined with anteroposterior stress radiographs [7]. CT is well recognized for accurately evaluating tunnel positioning, orientation, and tunnel width in these patients [7]. In symptomatic patients after ACL reconstruction, magnetic resonance imaging (MRI) and boneSPECT/CT are both proven useful diagnostic tools [54]. Similarly, this is true for all ligament reconstruction surgery. 3