患者女,22岁。因“左踝疼痛3年余,加重3天”入院。患者3年前无明显诱因出现左踝关节疼痛,疼痛间断发作,活动后加重,休息时减轻,曾外用药物治疗,效果不佳,3天前疼痛症状加重。体检:右踝关节压痛、稍肿胀、活动受限,皮温正常。四肢肌力及感觉未见明显异常。影像学资料:左踝关节正侧位X线片示左胫骨下端一多囊状透亮区,呈偏心膨胀性生长,向外踝侧膨胀为主,其内可见骨嵴与骨性分隔形成,病灶边界较清,周围可见硬化缘,骨皮质变薄。后缘见骨皮质部分缺损,断裂部位软组织内可见稍高密度肿块影,未见骨膜反应(图1、2)。左踝关节MRI见左侧胫骨远端后份团块状异常 Female patient, 22 years old. Because “left ankle pain more than 3 years, aggravating 3 days ” admission. 3 years ago, there was no obvious incentive for patients with left ankle pain, intermittent episodes of pain, aggravated after exercise, and relieved at rest. External drug therapy was ineffective with aggravated pain symptoms three days earlier. Physical examination: right ankle tenderness, a little swelling, limited mobility, normal skin temperature. Limb muscle strength and feel no obvious abnormalities. Imaging data: the left ankle is the lateral X-ray showed a lower left tibia of a cystic translucent area, was eccentrically dilated growth to the lateral expansion of the lateral malleolus, which can be seen in the formation of bone ridge and bone separation, the lesion border More clear, visible hardening around the edge, cortical thinning. Posterior margin of the cortical bone defect, the soft tissue of the fracture site can be seen slightly higher density mass, no periosteal reaction (Figure 1,2). Left ankle MRI see the distal mass of the left tibia block mass abnormalities