My Daughter Has 5 Small "beady" Bumps Under The Skin

my daughter has 5 small "beady" bumps under the skin on her right knee you are unable to see them but they move around just like beads... and you can feel them. They are painful when she presses on them and she cant recall falling she is 17 years old and she Is not active at all... but she did have injuries as a small child in gymnastics, and volleyball.