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1.The x-ray suggest there is
soft tissue swelling, it can be possible when there is muscle thickness increased the density will be seen as swelling.
2.The possible cause could be inflammation after a trauma /
injury to the joint.
3.The treatment of choice in this case will be anti inflammatory medications and antibiotics with symptomatic treatment.
4.If not responding
MRI knee joint is the ideal investigations of choice for joint space, ligaments , bursae,
cartilage.
5.As a remedy reduce mobility and minimal exercise for free movement of the joint. So suggest to visit as suggested. Good luck.
Hope i have answered your query,
any thing to ask do not hesitate to ask.
http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888