avulsed fragment The visible ossified fragment may be small because the tibial spine is mostly radiolucent cartilage Dislocations In a child, the knee joint itself rarely dislocates; usually, the distal femoral or proximal tibial epiphysis separates first Dislocation occurs more frequently after the growth plates have closed and usually with trauma that involves significant force, such as a motor vehicle collision or contact sports The knee will appear obviously deformed with the tibia or femoral condyles abnormally prominent in an anterior or posterior dislocation, respectively Disruption of the popliteal artery may occur with the dislocation, and the resulting hypoperfusion may be limb threatening Posterior tibial and dorsalis pedis pulses and peroneal nerve function (sensation between the great and second toe and ankle dorsiflexion) must be documented Radiographs will confirm the diagnosis