Sometimes this kind of pain is just a chronic problem. Getting a bike with some form of automatic transmission would eliminate the need for the clutch lever. As would switching to a scooter. Before you dismiss the scooter idea, take a look at some of the larger scooters on the market like the Suzuki Burgman which comes in both a 400cc and 650cc version, the Kymco line of scooters, and both Honda and Yamaha make a 300cc scooter (as does Vespa). Any of these scooters will eliminate your problem, are capable of highway speeds, and often are as capable and as fun to ride as any motorcycle. A number of years ago, after going through double knee replacement, I gave up my Kawasaki Concours and bought a Honda Silverwing megascooter. It could ride at well over 100mph, handled superbly and had as many bells and whistles as most top of the line touring motorcycles. You need to think of scooters as an alternative to just quitting riding.