It can be a ligament tear but it's most likely to be a meniscus tear. Both conditions will not be visible on x-ray but can be seen on MRI scan. MRI scan can be done in government medical college at very little cost. In private centers it usually costs ₹5000 to 8000. I have yet to find any centre charging ₹18000 for it.
Next Steps
Find a scan center in Google and call them to get price quotation for MRI of knee ( without contrast)
Health Tips
If you need a prescription I will be happy to provide it to you.