About 5 years ago, I found that kneeling caused a severe cramp-like pain in the back of my calves, also in the back of my thighs. Slowly, this has got worse and for about a year now, some pain is also there when lying down or in the morning. But as soon as I get up and walk, there is no pain at all and I can run and walk without any difficulties. Stretching exercise appear to ease it. Once I forgot myself and knelt quickly, resulting in collapsing with a severe cramp-like pain throughout my whole body. Recently, I noticed a similar slight pain in my upper left arm.