Thank you for choosing Doctor Spring. Your symptoms suggest of a baker's cyst or an acute episode of osteoarthritis. Your photos show a clear swelling localized right at the back of the knee with slight swelling in the front of the knee.
Bursitis, tendinitis, ligament tears usually cause pain in the knee, but are not limited to just the back of the knee. So most likely this is Baker cyst.
Baker's cyst is usually due to leakage of joint fluid from the knee. The inflammation after accumulation of fluid can happen due to osteoarthritis (wear and tear) of the bone which is common in menopause or with aging/over use.
But do not worry. Most cases will resolve by itself. But you should see this as a warning sign. This is good time to get your knee joints and bone health tested. In rare cases this cyst can rupture and cause acute swelling in the lower leg, so it is important for you to get in touch with your orthopaedician /GP for examination and investigations like ultrasound and/or Xray.
Baker's cyst is treated with removal of fluid from the cyst, which is done by using cortisone injections. If your doctor determines arthritis in the back ground you need to take steps to manage this condition(rest, ice pack, compression and elevation of the joint; OTC pain relievers and anti-inflammatories, physical therapy) there by preventing the recurrence of baker's cyst.
For now take rest as much as possible with knee in a non weight bearing position. You may take a NSAID medication like Ibuprofen 400 mg twice daily in consult with your Doctor.
Hope this helps.
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