If there is any swelling in the knee then there is damage happening causing the joint surfaces to leak fluid in a desperate to attempt to immobilise. As long as there is fluid in the joint the message is to take it very carefully.
Love your knees and they will repay you with a lifetime of faithful service
Glucosamine is worth taking but is limited on its own. Chondroitin helps hydrate the cartilages and this is more important for knee health as one gets older and cartilages tend to become dry and brittle. MSM (methylsulfonylmethane) aids cartilage healing and cooling any inflammation. If there is swelling in the joint then MSM should be on the list. The Best supplement for you to take is Joint Factors 4500.
Sardines are fine as is flax seed. Be aware that most people have far too much calcium in their diets and this will contribute to joint arthritis, tired muscles and susceptibility to injury. You can find reference to this in earlier posts on this site. ensure that there is protein in every meal, beginning with breakfast.
Consider obtaining a Hair Tissue Mineral Analysis. Again, you will find many articles on this site about this most useful test.