Sir,
Have you got any X-Ray done. If not do it as soon as possible
May be because of your bad posture your back pain has arise. Do apply hot pack twice a day. And have you fallen anywhere as your knee get injured. May be its because of OSTEOARTRITIS. kindly get your X-Ray done.
Next Steps
See any good Ortho Doctor and get your assessment done. and after that you can visit a good physiotherapy centre
Health Tips
avoid complete knee bending and stairs climbing