PATELLA DISLOCATION

PATELLA DISLOCATION - The patella can dislocate outside of its normal position, usually round the outside of the knee. It can also partially dislocate, called a subluxation. Pain will be felt immediately at the time of injury. There is likely to be swelling in the knee joint and there will be an obvious displacement of the kneecap. Often the kneecap may briefly dislocated and then return to its normal position, although pain and swelling will usually be present. The patella normally lies within the patellofemoral groove and is only designed to slide vertically within it. Dislocation of the patella occurs when the patella moves or is moved to the outside of this groove and onto the bony head of the femur. The patella may also sublux rather than fully dislocate, meaning it moves partially out of position. A patella dislocation is not the same as a dislocation of the knee joint itself which is a much more severe traumatic injury. 

It is usually a result of an acute blow or twisting action of the knee. In most cases the patella will relocate to the patellofemoral groove on straightening of the knee, however this is usually extremely painful. The factors which make a patella dislocation more likely are insufficient quadriceps strength on the inside of the knee, over pronation of the feet and an what is known as an increased Q angle of the knee.