目的研究X线、CT、MR的膝关节 剥脱性骨软骨炎(OCD)的影像学表现，并 比较三种检查方法的对病变的诊断价值。 方法 回顾性分析38例(41只)膝关节镜及 手术证实的OCD的X线、CT、MR征象，评价 剥脱性骨软骨炎的影像学特点。结果 (1) 病变好发于股骨内侧髁(30只73.2%)。(2) 其X线表现为有小骨片自关节面剥离，骨 片密度较高，边缘锐利，周围有透亮线环 绕，其下为容纳骨片的骨床，可见明显的 硬化边。(3)CT表现为在缺损的骨破坏区 可见未脱落的死骨片，部分可见到一个大 部分呈游离状态的骨片的一端仍连在关 节面的骨皮质上。(4)MR表现为关节软骨 下局灶性小病变，病变在T1WI上呈低或等 信号，有低或高信号带环绕在病变周边， 软骨下骨板变薄或消失，部分可见关节软 骨断裂或消失。(5)MR对病变的检出率较 高。结论 OCD的X线、CT、MR表现比较独 特，MR可对其作出较明确的诊断。

Objective To study the X-ray, CT, MR of the knee joint osteochondritis dissecans (OCD) imaging findings, the value in diagnosis of lesions and to compare the three methods of inspection. Methods Retrospective analysis of 38 cases (41)of CT, MR and X-ray findings that were confirmed OCD by knee arthroscopy and operation , and evaluated the imaging charateristics of osteochondritis dissecans. Results (1) the lesions occurred mostly in the medial femoral condyle (30 73.2%). (2) the X-ray image was manifested as ossicles peeled from articular surface , the density of them were higher, their edge were sharp, which were surrounded by bright line , and below them were bone bed to take them in with harden edge. (3) CT showed destruction of bone in the defect area as visible sequestrum, which did not fall off and can see part of them with one end of a bone at mostly free state remains connected to the bone cortex of the articular surface. (4) MR showed the performance of subchondralfocal focal small lesions, which appeared low signal on T1WI, low or high signal in the peripheral band around the lesion, the subchondral bone plate thinned or disappeared, part of articular cartilage fractured or vanished. (5) MR for lesion detection rate is higher. Conclusion X-ray, CT, MR expression of OCD is unique, MR can make a clear and definite diagnosis of it.