Whereas rheumatoid arthritis is an autoimmune disease that causes joint malfunction due to inflammation, osteoarthritis is a mechanical disease brought on by the destruction of joints through wear and tear. Osteoarthritis is the most common form of arthritis, with approximately 27 million Americans over the age of 25 having been diagnosed with it.
A blood clot is a thick mass of menstrual blood that is expelled from your body when you menstruate. Clots are most common during the heaviest part of your flow â which is usually the first few days. Blood Clots look like chunky, jelly-like blobs that vary in size and color.
There is also a chance that your black period blood is caused by an infection or STD. Uterus infections can cause blackening as well as many STDs. Women that have sex during their cycle also experience black bleeding because the blood was pushed back into the vagina and can become trapped as a result.