Thank you for choosing DoctorSpring,
Although I not unable to examine your Physically from the history you provided I have some differential diagnosis.
One can have different size on right and left side and it is a known medical fact. The frequent fall and injuries on left side can be because of LLD (limb length difference). Your diabetes can cause peripheral neuropathy leading to poor peripheral sensation, which contributes to fall.
The knee swelling is because of effusive osteoarthritis. ankle swelling can also be because of osteoarthritis. Since there was excess stress in the left limb secondary osteoarthritis is highly likely. Moderate arthritis can cause swelling. But your leg swelling is more diffuse (not limited to the joints alone). So we need to consider other possibilities here. The most important concern here is a DVT (or Deep Vein Thrombosis ). Your Doctor would have already ruled it out. The ultrasound like machine is actually a Doppler machine to assess the blood vessels.
Other possibilities are a postphlebitic syndrome and a Lymphedema. Unfortunately without further evaluation I will not be able to give a single diagnosis at this stage. I recommend this approach - Discuss with your Doctor whether DVT (or any blood vessle problem has been ruled out). If yes, then you can judiciously have a wait and watch approach for a week or two. You can take a NSAID anti inflammatory medication in the guidance of your Doctor. There is good chance the swelling will reduce with medication and rest.
Hope this helps
Feel free to ask followups / clarifications