What is the difference between Laxity vs. Instability?

LAXITY VERSUS INSTABILITY: IS THERE A DIFFERENCE?

I was at a course recently and an attendee asked a question about shoulder instability versus laxity. You may have heard those terms before and they are used interchangeably quite often incorrectly. Unfortunately, the answer to the question wasn’t properly addressed. So, I figured I would try and clear this up in case others are having similar issues.

First, laxity is essentially overall “looseness” of a joint. It is typically hypermobile in all directions. You might see laxity in gymnasts, dancers, swimmers, or other athletes that are excessively flexible and routinely place their joints in the extremes of motion. That being said, they may be completely asymptomatic because they have the muscular control and the ability to stabilize the body which can overcome the laxity. You can be lax but not be unstable.

Instability, however, is associated with pathology. An athlete may have had a history of dislocations or subluxations which makes them at risk for future subluxations or dislocations. These are the athletes that may reach overhead during an athletic contest and the shoulder might “slip out”, or sometimes, even during benign activities such as combing one’s hair. If you are unstable, you lack both the muscular and neurological abilities to keep the joint stable. So, you can be unstable without being lax. Often, there may be an instability in one direction, but not all directions of shoulder motion.

Hopefully, that makes sense. It will be up to you and your doctor to decide if you need surgery or if your condition can be managed with rehabilitation. I think it’s always a good idea to try conservative measures like physical therapy and activity modification prior to rushing to surgery. That may sound self-serving since I am a PT, but let’s be honest – if you can avoid going under the knife, why wouldn’t you?