Lumbar facet fracture-dislocation is rare, often due to hyperflexion with rotational force. Abnormal scoliosis on radiography is a key sign, prompting further imaging. Facetectomy and laminectomy ensure safe reduction, while instrumented fusion is an effective surgical treatment. Traumatic lumbar facet dislocation is an uncommon condition, particularly when unilateral lumbar facet dislocation is accompanied by a contralateral facet fracture. The patient had a locked facet joint at the left L4-L5, a fracture of the right superior articular process of L5 and a comminuted fracture at the peritrochanteric region of the right femur following a fall. Emergent operation was conducted, starting with open reduction and fixation for the right proximal femur, followed by posterior open reduction and posterolateral fusion with instrumentation, without interbody fusion, for the lumbar spine injury. The patient exhibited positive outcomes throughout the follow-up. This article highlights the trauma mechanism of lumbar facet dislocation, emphasizing hyperflexion with rotational force. Abnormal local scoliosis is a distinctive imaging sign of facet joint dislocation. Facetectomy and laminectomy are recommended for safe reduction and instrumented fusion is considered a safe and effective surgical treatment for facet joint dislocation injuries.