Bilateral cogwheel grooves observed on lateral condyles of femur and patellar articular surfaces: a cadaveric case report

The knee joint comprises the articulation of the femur and tibia, the femorotibial joint, and articulation between the femur and patella, the patellofemoral joint. In non-pathological anatomy, the articular surfaces of the femur, tibia, and patella are smooth, allowing for fluid motion of all joints associated with the knee. The bilateral knees of a cadaver were dissected and analyzed due to the presence of bilateral longitudinal, parallel cogwheel grooves on the lateral femoral condyles and dorsal surface of the patella. The evenly organized grooves are an odd occurrence, especially since very few cases have been reported. Termed Cogwheel grooves, they are grossly visible longitudinal grooves on femoral condyles and the articular surface of patellae that interlock together.  Health practitioners should be aware of the potential presence of cogwheel grooves in the knees. In knees with cogwheel grooves, the knee motion may initially appear appropriate with flexion or extension of the knee; however, restriction could be expected when lateral movement of the patella is facilitated. Depending on the depth of the cogwheel grooves, patients may be diagnosed with a hypomobile patellae, as the only way to likely manipulate the patellae laterally or medially would be to distract the patella to disengage the grooves prior to lateral or medial movement.