Does the fibrillation on the surface of the ACL joint cause your knee to slip and be instable?

No. Fibrillation means you have some roughness of the surface of the acl that dose not cause your knee to slip out, it is a sign arthritis or slight damage to the ligament. Good luck thanks.
Knee instability . If the acl has laxity or is torn the knee will feel like it is slipping. Fibrillation is not a typical description of the acl.