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I'm not sure I understand this, last I checked it's a socket joint. The thing that I have trouble grasping is not that the ball can come out of the socket, but how this can be done without the muscles and tendon's not twisting like a twizzler...The shoulder is not really much of a joint
OkThe shoulder joint is not really a "ball and socket" type of joint, like the hip, for instance.
It's more of a tightly packed assembly of bone, cartilage, ligament, tendon and muscles that create a joint assembly.
Does a dislocation of the shoulder revolve around the Glenoid cavity?Go give an idea of what the joint looks like on a skeletal level, check out the illustration.
View attachment 499686
Yes it does.Ok
Does a dislocation of the shoulder revolve around the Glenoid cavity?
It looks like the only thing that could rotate like thatYes it does.
The question is if one dislocated their shoulder like how Houdini and others did (I've seen people do it), how do the muscles not become twizzlered so to speak? Can the tendon and muscle slide around the bone?The Humerus is held in place against the Glenoid by the Bicep tendon and Rotator Cuff.
As possibly the most qualified here to answer this, here we go (though Mike has covered it well enough)...
Essentially some people have more elasticity in their tendons and ligaments than others which allows for the greater range of movement and the easier joint dislocation and relocation. There are a number of conditions that are known about that are hyper-mobility syndromes: Ehler-Danlos and hyper mobility (double jointed) syndrome.
Secondarily to this anyone who has previously dislocated a joint is more prone to do so again because of the laxity in the connective tissues that has been caused by the dislocation.
Now muscles don't get twisted into knots because there is enough play with them in their stretch to avoid this. That isn't to say that if you stretch them to far the won't break (partially or fully)and this is the cause of muscle strains/pulls/tears etc.
Now the connective tissues also can rupture, most people over the age of 70 will have some degree of rotator cuff tear in the shoulders. These tears happen in the same way as muscles with being over stretched e.g. Dislocations. They heal worse though because of poor blood supply.
Don't forget (and I love this name) The Fovea Capitis Femoris and its associated ligament. Ya gotta love those old anatomists (Hole in the Head of the Femur)holding the femur in place
Of course which in itself is the remnant of the foveal artery which supplies the femoral head in youth and whose degeneration is why the elderly end up with a hemiarthroplasty if they fracture intracapsularly the femoral neck...Don't forget (and I love this name) The Fovea Capitis Femoris and its associated ligament. Ya gotta love those old anatomists (Hole in the Head of the Femur)
So Dr Lahl wasn't telling me porkies thenOf course which in itself is the remnant of the foveal artery which supplies the femoral head in youth and whose degeneration is why the elderly end up with a hemiarthroplasty if they fracture intracapsularly the femoral neck...