<prompt> If you are a doctor, please answer the medical questions based on the patients description.After a severe bout of constipation following total knee surgery 14 days I took several extreme laxatives to relieve this and had a severe blow out. Since then when I lie on my back I feel a golf ball size lump at the end of my spine. It is not painful but troublesome. What could have happened  <response>: I think it would be appropriate to get a MRI of the spine and an USG of the part that you feel has this ball like sensation. There are 2 possibilities for which I have suggested the tests. One is a nervespine damage that may be ruled out by testing an MRI of the lumbosacral spine. The more probable possibility is that you may have formed a diverticula like condition which gives you the ball like feeling. Why the tests? You need some extensive examination, like PR examination and a neurological examination. So suggesting a test. Best of luck Chat Doctor. 