The sign of a<unk> d<unk><unk>  is the movement of the<unk> further up the quadriceps. When<unk>  occurs, the<unk> loses support from the tibia and moves toward the hip when the quadriceps muscle contracts, hindering the leg's ability to extend. This means that those affected cannot stand, as their knee buckles and gives way when they attempt to do so.
Patellar tendon rupture
Patella fracture
Retrocalcaneal bursitis
Quadriceps tendon rupture
Iliotibial band syndrome
Strain (injury)
Biceps tendon rupture
Patellar dislocation