HI, Thanks for the query. I understand your concern. You had already gone to ER for swollen & fatigued legs. You have high blood pressure / excess body weight too. In my opinion you need a more detailed study of your blood pressure / excess body weight .. which may lead to swelling of legs. possibility of diabetes needs to be excluded along with cardiovascular health. Baker s cyst ( a cyst at back of knee joint usually arises in cases with arthritis / pain in knee joint )on left side .. remains asymptomatic . It must be same in your case. That s why your doctor has not given you any specific treatment for it. HE has given you medicines for blood pressure & cholesterol control. * Now about your question. - The pain in your opposite leg can be from putting more stress on right leg( the left one being affected by knee joint arthritis. This results in muscular stress on right leg.. This can be managed by muscle relaxants oral or local ointment. & treatment of left knee joint & improved gate there after. - May be pressure on local nerve supplying to groin region ( Right )due to wrong g problem.gate to adjust left leg. This needs correction./ pain medication/ physiotherapy & management of left leg problem. - some times vertebral degeneration ( aging/ over use/ trauma ) or disc problem cause nerve pressure at spinal level to give the symptoms of pain & leg fatigue. Imaging Invstigations with an expert advise to detect exact site & cause of trouble followed by specific treatment would help you. Thanks.