It depends upon truma intensity, mode of trauma and pain level.it usually take 2 to 4 weeks if you take proper rest.it can heal automatically with rest.if symptoms persist u need to take Orthopaedic opinion.
Next Steps
as soon as pain subsides start knee mobilization.you can use hinge knee brace.you can consult online for detail treatment plan.
Health Tips
avoid strenuous activities and take rest.keep limb elevated.