Upon closer inspection, it can be seen that this "joint" doesn't have much in common with other joints in the body. Unlike most other joints, there are no classic joint partners here, such as those shaped like a ball or socket.

At the acromioclavicular joint, two bones are positioned side by side. To prevent them from colliding and to allow for mobility, a small disc is sandwiched between them. This disc is comparable to the intervertebral discs in the spine, which also act as a buffer and allow for mobility. The bones are surrounded by strong ligaments to keep the entire structure in shape. If the ligaments are injured, the bones can slip out of place. This is known as acromioclavicular joint dislocation or Tossy injury.