67 SPECT/CT in the post-operative painful knee screw. The most common reasons for persistent pain and limited range of motion are malposition of the graft or associated cartilage degeneration [11]. Osteotomy Coronal alignment (varus-valgus) significantly influences loading of the different knee compartments [12]. In a varus aligned knee around 70-90% of the loading runs through the medial compartment [12]. In a valgus aligned knee the lateral compartment is significantly more loaded [12]. This mechanical loading results in increased joint forces and wear of the affected knee compartment [12]. In patients with early OA or overloading symptoms alignment might be corrected by osteotomy of the femur, the tibia, or both [13-15]. The most commonly performed osteotomy is the high tibial osteotomy aiming for correction of a proximal tibial varus alignment. Two techniques are used, the medial opening or lateral closing wedge osteotomy. The medial opening-wedge technique is current standard of care. Another osteotomy, which is mainly used in valgus aligned knees is the distal femoral osteotomy (DFO), which is a reliable procedure to reduce the loading within the lateral knee compartment [13]. Valgus mal-alignment may also be attributable to tibial deformity [14]. Most common problems after osteotomy surgery are persistent pain within the unloaded knee compartment due to insufficient correction, loss of correction, pseudoarthrosis, overloading of the other increasingly loaded compartment, malposition of plate or screws, intraoperative fractures, change of patellar height, altered rotational alignment and neurovascular complications [15]. Subsequently, an osteotomy may cause osteoporosis due to the stress-shielding effect [16]. Meniscus surgery Themenisci are considered crucial structures for knee stability, shock absorption, and nutrient distribution to the articular cartilage [17]. Due to this important knowledge meniscus surgery has significantly evolved during last decades. In the beginning of meniscus surgery, complete resection of the torn meniscus was the reference standard. Nowadays after having recognized the deleterious effect of total or subtotal meniscectomy it is recommended to preserve as much meniscus tissue as possible [18]. Only unrepairable meniscus tissue should be resected [18]. In addition, many patients with traumatic or degenerative meniscal lesions can be treated non-operatively. In fact, this is true for all patients without locking of the knee joint, with pain responsive to pharmaceutical treatment, and stable meniscal lesions. 3