Hello, Wellcome HCM, Between two vertebrae, there s a cartilaginous disc which has outer cover of annular fibres and inner viscus fluid content called nucleus plulposus . In old age or in young age due to excessive physical stress these annular fibres undergo wear & tear and they become loose and overall cartilaginous disc bulges diffusely, in your case at L4-L5 and L5-S1 intervertebral level. This bulged disc comes in close proximity to spinal cord and spinal nerves behind them and it may compress spinal cord and nerves coming out from foramina (in your case S1 nerve root) which is a cause of pain, tingling and weakness in back and limbs depending on severity. Spinal nervers come out from the transverse foramen present on either side on vertebral transverse process. Physiotherapy can help to a great extent to this problem. But if it doesn t help discectomy or decompression surgery may need to be done.