Lining Up the Facts on Arthritis after Trauma

The topic of this report is how and why joint trauma leads to arthritis. Arthritis that develops after an injury is called posttraumatic arthritis. The authors review what is already known on this topic. They ask: Is this type of arthritis brought on by joint instability or joint incongruity?

Incongruity occurs when two sides of the bone or joint don't line up smoothly and evenly. Incongruity can be caused by a bone fracture or an injury to the joint. Instability means the joint is free to move too far in one or more directions. Many studies show that patients do pretty well when the joint is stable, even if there is a lot of incongruity. On the other hand, even a small amount of incongruity causes problems when the joint isn't stable.

Is there a link between joint incongruity and posttraumatic arthritis? Here's what we know so far:

  • Certain kinds of fractures of the lower leg bone are linked to posttraumatic arthritis.
  • A stable joint can handle surface incongruity.
  • Injury to the knee ligaments without fracture is linked to posttraumatic arthritis.
  • Incongruity of the knees and ankles is tolerated better than at the hip joint.
  • Instability affects the hip, knee, and ankle equally.

    In this study, surface contact pressure was measured at the ankle. A new real-time pressure transducer was used. Both incongruity and instability were tested at the same time. The researchers measured the contact stress on the ankle joint during walking. They were able to see how contact stresses change with time.

    The results of this study suggest that ankle instability leads to increase load on the joint. Ankles with identical incongruity had the same loads. This new method of dynamic joint testing opens the door for studying what happens in the joint after injury.

    This information may help doctors decide which is more important: lining up the edges of a broken bone, or stabilizing the joint. The authors say that knowing how joint loading occurs will help us understand how posttraumatic arthritis develops. Maybe then doctors can find better ways to prevent it.

  • Reference: 

    Todd O. McKinley, MD, et al. Incongruity Versus Instability in the Etiology of Posttraumatic Arthritis. In Clinical Orthopaedics and Related Research. June 2004. Vol. 423. Pp. 44-51.

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