Patellar dislocation is a painful injury that occurs when a person's knee cap pops "out of the joint" or "out of its socket" and remains out until they pop it back in.
Dislocated patella
Retrocalcaneal bursitis
Olecranon bursitis
Chondromalacia patellae
Prepatellar bursitis
Humerus fracture
Iliotibial band syndrome
Calcific tendinitis