We report a case of an avulsion fracture (sleeve fracture) of the proximal pole of the patella in an 8 year old boy who fell onto his left knee. After the fracture was diagnosed, the patient under went surgery on the day of the accident. The articular cartilage and the upper fragment were reconstituted and fixed with transosseous sutures. A cast immobilisation in extension was used for 6 weeks and the patient regained full active mobility of the left knee joint after cast removal. A radiograph showed that the fracture had completely united. Diagnosis, pathomechanism and treatment strategies are discussed with reference to this rare case, and the literature is reviewed.