A 77-year-old Caucasian man visited his orthopedic surgeon and complained about persistent right knee pain for the last 2 months. The patient did not remember a specific traumatic event in the past. Upon clinical examination, the surgeon suspected a degenerative meniscus lesion. Since the patient had a pacemaker, further evaluation with magnetic resonance imaging was contraindicated. Intra-articular steroid injection did not lead to a substantial improvement in the symptoms. Based on the available data, it cannot be definitely ruled out that CRPS was absent at that time. The clinical presentation however makes this scenario unlikely. Since the surgeon supposed that the pain was due to a degenerative meniscus tear, he performed an arthroscopic partial medial and lateral meniscectomy. Shortly thereafter, the patient complained of a dramatic increase in pain intensity and on inspection the surgeon described a newly developed soft tissue swelling, skin color change and hyperhidrosis. He referred the patient to our institution for further evaluation and treatment because he suspected a case of CRPS 1. Upon examination, the patient was afebrile and complained of consistent pain and soft tissue swelling over the right knee. Due to pain, the patient used two crutches for independent ambulation and was able to walk approximately 30 m. The right knee showed vasomotor (slight rubor, locally increased skin temperature) and sudomotor changes (slight hyperhidrosis). Active and passive range of motion was painfully limited to flexion/extension of 40°/20°/0°. He demonstrated tenderness on palpation of the medial femoral condyle. Ligamentous stability and meniscal integrity could not be examined due to the pain. Laboratory testing showed the following results: Hb of 12.2 g/dl (<14.0–18.0), ESR 83 mm/hour (8), AP 106 U/liter (40–129), CRP 38.9 mg/liter (<5). Plain radiographs revealed moderate degenerative changes and a moderate intra-articular effusion. Computed tomography (CT) showed some nonspecific trabecular changes in the medial and lateral femoral condyle. Finally, triple phase bone scan with Tc-99m-DPD revealed an increased activity inflow into the distal femoral diaphysis and epiphysis during the perfusion stage. During the second and third phase of the bone scan, multiple enhancements in the distal femur, the right tibia and right hemipelvis were detected. Based on these findings, we concluded that a metastatic process caused the painful swelling and dysfunction. Further evaluation with a biopsy of the femur and cystoscopy revealed the diagnosis of a metastatic urothelial carcinoma. The location of the primary tumor remained unclear and was not further investigated due to the progressive worsening of the patient. After initiating palliative chemotherapy, the patient's condition rapidly deteriorated and he passed away within a few weeks.