As per the details given in the question, it seems to be an injury
to the anterior cruciate ligament
of the knee. For this yo should immediately review with orthopaedic surgeon
as a collection of blood in knee (hematoma
) is very common with this injury and as you are telling the knee is bit swollen.
The accumulated blood need to be aspirated at earliest as it can become a source of infection. Then you need to get an MRI
of the knee. Till then after aspiration of blood a knee cap or compression bandaging may be given, Specific treatment depends on the injury pattern seen in MRI and on the daily living activity of the patient.