53-year-old woman with limited motion and pain in knee

The patient is was a 53-year-old female who experienced a fall, landing on her knee, several hours before presenting.

Her knee is stable and she is able to bear weight on the affected leg, though there is mildly decreased range of motion due to generalized pain in the area. You note that the pain is not over the patella, however. There is no fluid in the knee. View the image taken and consider what your diagnosis would be.