not sure what is causing or what did cause inflamation (tear, sprain, strain) but I only know that a chiropractor or doctor ( or even a non professional) can test : laying down, extend leg, and apply lateral pressure…
at least you can kind of sense the amount of inflamation, and perhaps damage.
a professional can assess a lot more the exact amount of damage to the ligament.
at any rate, R.I.C.E. is necessary.
if kinda bad, you might have to just stay off it until it heals. Ligaments take about 3 months to completely heal… much longer than muscle.
-if you think its not too bad, I would suggest you do a stretch routine on adjacent leg muscles that if tight, will create compression or pulling on that ligament. in particular thigh adductors. Ofttimes minor pain in knee area is caused soley by tight adductors.
look for any and all thigh adductor stretches that can be safely done, including assisted. If you get assistance, some deep tissue compression/traction, myofascial stretching massage on adductors will be good.
check out lower leg stretches and massage as well.
-any and all leg and hip muscles to balance the whole.