Hello Kathy,
Welcome at HCM.

I have read complete details of your question.

The degenerative disc disorder & arthritis at back can lead to back pain or back pain with radiation of pain in lower limb.

The bruise is not due to DDD OR ARTHRITIS.

There are some reasons for that like-

-Bleeding disorders.

-Deranged clotting factors due to liver disorders.

-Medicines which does lead to platelet disorders.

-Injury.

-Blood vessel tumor like hemangioma.

If this is gradually increase then you should be concerned about this & should get your self checked by having detailed blood examination.

Hope this will help you.

With best wishes.

Hello and Welcome to HCM,
Thanks for writing to us.
The sudden onset of a bruise of unknown cause should not be taken to lightly, this could be an indication of either a blood clotting problem (low platelet production or increased rate of removal of platelets from blood), a reaction to any medications you could be taking (eg. aspirin, coumadin, some pain management medication, etc.), accidental ingestion of a poisonous substance (eg. rat poison, etc.).
It is best you just visit a doctor for a blood work up, once all the results return normal, there should be absolutely nothing to worry about, and this bruise could have been caused accidentally (like scratching yourself while you were asleep, etc.).
Hope this helps you.
Wishing you good health...
Regards.
Dr Saurabh Gupta.
Orthopaedic Surgeon.