People often describe pain as being "inside the knee cap." The leg tends to flex even when relaxed. In some cases, the injured ligaments involved in<unk>  do not allow the leg to flex almost at all.
Patellar dislocation
Patellar tendon rupture
Patella fracture
Knee dislocation  Knee dislocation  1
Knee dislocation
Acetabular fracture
Hip dislocation
Humerus fracture