I found an almost month old calf stumbling on its rear wheels tonight that stands with a slight upward arch to its back when still. Its hock and hip appeared stiff when moving. I guessed it had been stepped on when first seeing it, but found no scuffs and it didn't react to any tender areas. The spine, tail, ribs, and hips all felt normal to touch, it holds its head balanced and normal, and all joints flex as they should. Its effort to walk and talk seem normal and its tongue, eyes, and temp seem fine. It tries to keep up with momma, but it's rear will dog leg to the right as if it's pulling out to pass its front when it gets in a hurry. Heals click and down it goes. It might have a slight case of the scours but the cow is a big milker. No blood in urine or stool. ~3 hours later, right before dark, it appeared to have more flex in its hock but still showing symptoms.

This is when I noticed the cow had an abnormally large low water belly on the right side and was slightly bloated on the left. Her milk looks normal to maybe a little thin with no blood or excess bag heat or tenderness. She has access to grass hay but the grass is fresh and the whole herd is very loose. None of the other cows show the belly or bloat. She has access to high mag mineral and we've never had an issue with selenium as far as I know. She seems normal otherwise, but I can't help but think the two are related. I know jack about bad weeds, but we've never had an issue in this pasture as far as I know.

Any guesses or suggestions?