The fingers you mention are run by different major nerves.
The thumb, index finger and middle finger come off the carpal tunnel, running off the median nerve. The ring finger and pinky run off a different nerve, the ulnar nerve.
http://morphopedics.wikidot.com/hand-evaluation
Having that Middle finger locking suggests it is not all nerve related.
The hand may lock up because of a tendon issue... this is called trigger finger. It has to do with tendons getting stuck when they should slide easily.
This is a Google image search for trigger finger:
https://www.google.com/search?q=trig...IVwxk-Ch2xugxW
Spasms in the forearm can also cause contractures. An imbalance of calcium to magnesium may cause muscles to contract when they are not wanted. Lesions in the spine may also do this.
You might have to see a hand specialist if it continues after using simple remedies like magnesium supplements and/or magnesium lotion.
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All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
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Weezie looking at petunias 8.25.2017
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