Twisting injuries followed by swelling in the knee can be due to damage to any of the multiple structures inside the knee. It can be the ligaments, meniscus
Ligament injuries give a feeling of instability on walking with pain. Meniscus injuries can cause locking, difficulty in fully straightening and pain.
You require to see an orthopaedic doctor who will examine you and may ask for x rays and scans; and plan an appropriate treatment for you.
You can contact me in case you require further assistance.