on the back of knee, varicose veins
indicate one of the following causes of your symptoms:
Ruptured varicose vein as you have mentioned.
Morrant Backer's cyst
that is coming from the knee joint.
This can be diagnosed well by the following ways:
Consult an Orthopedic Surgeon get MRI of the knee joint and around.
Color doppler of the lower limbs
to know the status of the varicose veins.
The treatment will obviously be as the per the findings.
Till then use compression bandages.
Do not strain more on the affected knee.
Backer's cyst and varicose veins will need a proper planned surgery.
Hope I have answered your query. Let me know if I can assist you further.
Dr. T. Chandrakant, General Surgeon