RT Journal
A1 Sillanpää, Petri J.
A1 Paakkala, Antti
A1 Paakkala, Timo
A1 Mäenpää, Heikki
A1 Toivanen, Jarmo
T1 Displaced Longitudinal Stress Fracture of the PatellaA Case Report
JF The Journal of Bone & Joint Surgery
JO The Journal of Bone & Joint Surgery
YR 2010
FD October 6
VO 92
IS 13
SP 2344
OP 2347
DO 10.2106/JBJS.I.01472
UL http://dx.doi.org/10.2106/JBJS.I.01472
AB 
Stress fractures often occur in physically active individuals as a result of repetitive strenuous muscle and tendon forces acting on bones that have not adapted to such forces1-3. To our knowledge, the literature contains no reports of displaced longitudinal stress fractures of the patella requiring open reduction and internal fixation. The quadriceps muscle and patellar tendon produce extensive forces that can result in a displaced transverse patellar stress fracture2-7. The less strong vertical patellar restraints, including the medial patellofemoral ligament8, produce most of the ligamentous patellar stability in the lateral direction near knee extension8. In cases of acute traumatic patellar dislocation, the osseous structure of the patella is compromised mostly in the lateral direction—e.g., by avulsion of the medial patellofemoral ligament insertion—causing a medial margin fracture of the patella9. We are not aware of any previous reports of repetitive stress causing a displaced longitudinal patellar stress fracture.