Arthro-IonX could be helpful especially if the ligament is not completely torn. If it is completely torn , the knee needs to surgically stabilized if the muscles can't hold the knee joint from rubbing. It it is rubbing, Arthro-IonX might be able to lessen the discomfort.
There are supplements that can be used as building blocks to repair a stretched or partially torn ligament. Standard Process has one called Ligaplex. We also recommend Arthro-IonX to stimulate healing. The oligotherapeutic mineral base found in Arthro-IonX helps the body to better utilize the other nutritional substances given for a synergistic response. Other supplements I recommend are MSM, Canine Probiotics, and Omega 3,6,9.
Also be sure to give sufficient fresh water that is free of chlorine and fluoride. If you can gradually phase into a grain free diet that can be helpful too. The other thing that is sometimes beneficial is to have a certified veterinary chiropractor check for spinal and hip alignment and make any necessary corrections. This can reduce the amount of abnormal stress on the knee and reduce the chances of the other knee being damaged. Dogs that tear one ACL have a 80% chance of injuring the other side.
Please let us know how you progress or if you have any other questions.