Is there a medical complaint known as melodeon knees?
In a word - no. But the metal in some artificial knee designs is magnetic. It stops them setting off terrorist alarms in airports, and also helps keep their components located 'anatomically' (the surgeon will leave the natural ligaments intact - unless the op was for trauma).
There are anecdotal reports of this causing problems with musical instruments. Steel guitar strings seem unaffected though the wound strings on cellos seem to change tone, if not pitch.
It's believed that the vibration of a steel reed (especially the longer low ones) sets up eddy currents though the block that are then open/close circuited in a complex way as the tongue moves.
I don't personally have a PhD in electrophysics, so this is very much the simple man's explanation.
The problem may be improved as you get used to the different 'attack' on your instrument, and nearly all physiotherapy departments will have someone interested in '
Faradism'
Otherwise - my own university(!) is investigating
methods of de-Gaussing which look promising.