You most likey have something called Dupuytren's contractures.
This is thickening in the fibrous layer that lays beneath the skin of the palm of the hand.
As this thickens, it leads to tightening which causes the fingers to curl towards the palm.
Nodules can also form, which are what you are describing as lumps in the palm.
The cause of this disease is unknown, but diabetics are more prone to developing this.
People who use their hands repetitively also develop this more commonly.
It is seen more frequently in people who drink alcohol, especially in excess.
If the disease/contracture is mild, stretching exercises to keep the fingers moving fluidly are recommended.
Steroid injections into the palm and nodules are the next step.
Lastly, surgery can be done.
Here is more information for you if you would like to read about it.http://orthoinfo.aaos.org/topic.cfm?topic=A00008
Feel free to ask any follow up questions you may have and I will be happy to discuss further,
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Edited by Dr. Abby on 2/19/2010 at 7:03 PM EST