Re my left gastrocnemius muscle ( i believe - from a horse anatomy illustration ) . About 5 weeks ago I had a complete left knee replacment April 28 ,2014 .Everything has gone very well , including the ability to walk unaided from day 5 ,& normaly up stairs from week 3 . Now , however about 4 days ago I went to a Gym to practice on a atationary bike as advised . Lifting & moving the left leg in front of me over the center mechinism , I may have strained the above muscle with a slight twist . Knowing not to do what hurts I have not been back , but that muscle hurts @ about 4 t0 6.5 level . In addition the leg now hurts a great deal while lying down . Normal activity does not present a problem ,except moderate standing . What would be your suggestion to ease the discomforts & be able to return to strenghtenging activity . Fran Marcoux . I can supply other info as you request .