Introduction: We report the case of a lateral uni-condylar fracture of the femur type Trélat associated with a dislocation of the patella, which posed a diagnostic problem for us. Observation: This is a 26-year-old patient who suffered an open trauma to the right knee following a motorcycle accident. We mentioned the diagnosis of a Trélat fracture associated with an avulsion of the patella. Indeed we had difficulty recognizing the dislocation of the knee on the radiological incidences of the front and profile of the knee. The diagnosis of patella dislocation incarcerated in the condyle was only made intraoperatively. We performed trimming of the wound, reduction of the patella and osteosynthesis of the condyle. Conclusion:A careful radiographic examination is essential for any uni-condylar fracture of the femur because of the possible lesional association of the patella and the tibial plateaus.

Report case: A 30-year-old patient presented knee pain associated with swelling of the distal third of the thigh as a result of a sports trauma. The diagnosis of a Brodie's abscess was made. Surgical treatment combined with antibiotic therapy was performed. The evolution was favourable. Conclusion: Brodie's abscess is a subacute osteomyelitis that can pose a diagnostic problem with bone tumors. Magnetic Resonance Imaging has a place in the diagnosis. Patient management must be multidisciplinary.