Patellar Instability can dramatically reveal itself with a sudden episode of dislocation of the patella (kneecap).
Although most people are familiar with the distress experienced by someone who has had a dislocated patella, fewer realise that instability can range from nagging pain in the front of the knee, without any obvious instability, through episodic 'giving way' when the patella almost derails but not quite, then there may be dislocation events where the patella jumps right out of the groove.
The continuum continues on to more severe instability where the patella habitually dislocates with every knee bend, and right up to rare cases where the patella is permanently dislocated and never goes back into the groove.
Dislocated kneecap versus dislocated knee
Please be aware that a 'dislocated kneecap' or patella is a very different condition from a 'dislocated knee'. A dislocated knee is a catastrophic injury, ripping several of the major knee ligaments connecting the two long bones. In a dislocated kneecap, in contrast, the two long bones are still well connected together via their ligaments. It is the kneecap that moved from its alignment, and some of its local ligaments may be torn.