You have not mentioned your age. Your back pain
and knee problem may be two different problems.
Knee joint pain may be due to arthritis
- need Digital X-ray knee joint - to rule out arthritis.
Lower back pain - lying flat on the back gives comfort - indicates some spinal problem - needs MRI
lumbar and lumbo sacral joint.
may give temporary relief. Find the root cause and follow the instruction and treatment. You will be alright.