A patient presents with long time history of knee pain suggestive of osteoarthritis. Now he complains of unilateral lower limb swelling and on examination

A patient presents with long time history of knee pain suggestive of osteoarthritis. Now he complains of unilateral lower limb swelling and on examination there is +ve pedal & tibial pitting edema. What is the next appropriate investigation?
a) CXR
b) ECG
c) Echocardiography
d) Duplex ultrasound of lower limb
• Osteoarthritis relief by rest. So, immobility pt. can lead to DVT.