What are the symptoms of a hairline fracture in the patella?

It should show up in xray imagery as a thin white line, especially if the image is taken while the area isn't swollen. Other symtpoms include a large hematoma on top of the patella that is itself topped by a "fat cap" -- fat or marrow from inside the bone that has leaked out and floated to the surface of the hematoma. Also, most fractured patellas are proximally displaced (although other displacements are possible). Lay the patent down and compare to the non-injured patella for positioning. One test for a more seriously fractured patella is to lay the patient on their back and ask them to attempt to perform a leg lift with the injured leg -- no more than 10 degrees, or to the point it hurts. If the patient cannot lift the leg (regardless of pain), this is an indication of a fracture, as the connective tissue bonding the quadriceps to the back of the patella is not getting sufficient leverage to lift the leg. This can be a very painful injury. All evaluation should be performed in a manner that does not increase patient suffering, or skipped altogether. This injury and other patellar injuries like it respond very well to cold packing. 10 minutes on; 10 minutes off.