We report on a 61-year-old female patient who was referred to our department of traumatology from the department of dermatology within the University Hospital of Zurich in August 2018. The patient described cystic changes of the right lateral proximal lower leg since approximately one year. Initially, according to the patient, there was one large cyst which burst and subsequently, multiple new smaller cysts occurred. These small cysts are intermittently progressive in size with independent regress. She did not report any impairment of every-day life, nor pain or gaiting problems but felt disturbed by means of cosmetics. On physical examination, there was no pain, full range of motion, no clinical signs of lesions to the menisci, no clinical signs of joint effusion, no axis deviation or pain in valgus or varus stress. Also, the cruciate ligaments were unobtrusive and clinically, no signs of inflammation were present. The only abnormality found in the clinical examination was multiple cystic soft tissue tumors located on the lateral proximal right lower leg. The previously performed MRA (Magnetic Resonance Angiography) revealed subcutaneous tubular cystic lesions in close proximity to the lateral joint space, consistent with a ganglion system originating from the lateral knee joint (Figure 1). We suggested arthroscopy of the right knee and complete resection of the cystic lesions. The patient agreed to the suggested procedure. Two months later, the preoperative follow-up did not reveal any clinical changes (Figure 2). We then performed a total open excision of the ganglion system under general anesthesia and preoperative antibiotic prophylaxis. We took tissue samples for histological work-up as well as bacteriological swabs for further testing. After closure of the ganglion neck which had a connection to intra-articular (Figure 3), the wound was closed in standard fashion. We then performed a diagnostic arthroscopy which revealed grade 2-3 chondromalacia according to Outerbridge [7] in the lateral and medial condyles of the femur and bilateral tibial plateau. Furthermore, degenerative changes of the posterior patella as well as moderately irritated mucous membranes of the recessus. We also found some scar tissue pulling from the lateral meniscus to the base of the anterior cruciate ligament which we carefully resected. Other than that, no pathologies were found in the arthroscopy. Histological work-up revealed a simple ganglion system without any malignancy. In the bacteriological testing, no aerobic or anaerobic growth and no microorganisms were detected. The patient was discharged 2 days after surgery in a good state with full weight bearing of her right leg. Three months after the initial operation, the patient presented at our outpatients` clinic because of a new non-fluctuating, small, non-painful swelling on the right proximal lower leg (Figure 4). No wound-healing problems, no impairment of work- or daily-life were present. Peripheral perfusion, sensory and motor functions were normal. Clinically, we suggested non-specific swelling but considered reoccurrence of the previously excised ganglion and treated it with local application of heparin-diclofenac-plaster. 4 weeks later, the patient was seen again, and the swelling appeared to be reduced, the patient had no complaints, and we closed the case.