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What Causes an Arthritic Joint to Lock?

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Updated April 28, 2014

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Question: What Causes an Arthritic Joint to Lock?
It used to happen to my knee before I had a knee replacement. My husband's fingers would also do it. I'm talking about joints that lock. It's almost a bit shocking when it first happens. Your joint locks, and you can't get unstuck. Usually, it's painful when a joint locks, too.

What causes a joint to lock? What can be done to either prevent a joint from locking or to treat a joint that locks?

Answer:

Rough Edges

With arthritis, as cartilage wears away, the ends of the bones that form a joint become rough. With severe disease, bone rubs on bone.

As the joint moves, the rough edges can catch on one another. When the rough or uneven surfaces of the two bones that form the joint come into contact, it is possible for the joint to lock. The joint is not permanently locked, but you have to force it out of that position and allow it to move again. Sound painful? It can be.

Joint locking can also be caused by loose material in the knee, such as bone or cartilage fragments, or by a torn meniscus.

Bony Projections or Outgrowths

Along the rough edges, bone spurs or bony projections (osteophytes) can develop. Bone spurs can rub against adjacent bone or even nerves that are close by. Bone spurs can also be found where ligaments and tendons connect with bone. Most bone spurs cause no problem, but others can be painful and can cause a joint to lock. It depends on their location.

The Bottom Line Solution

To eliminate the problem of a joint locking, surgical removal of the offending bone spur is an option. Arthroscopic surgery can remove loose bone fragments and smooth out the rough edges. The ultimate surgical solution is a joint replacement for patients with severe joint damage. Often, cortisone injections are given in the affected joint to decrease inflammation. The injection should help with pain.

Sources:

MP Joint Locking. Duke Orthopaedics/Wheeless' Textbook of Orthopaedics.
http://www.wheelessonline.com/ortho/mp_joint_locking

All About Osteoarthritis. Joint Freezing. Page 73. Nancy E. Lane, M.D. and Daniel J. Wallace, M.D.
Oxford University Press 2002.

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