I've never heard of MAP5, but here we use legend, and it works great, but we have it done intra(somethingoranother) - in the joint. The legend shot is supposed to work for months, but we use adequan once a week to make it last longer.
Also, food for thought: hyluronic acid and glucosamine are not as readily absorbed by the body through feeding as they are through injection. MSM is readily absorbed through the body, and is an anti-inflammatory (cheap to feed, too!)
IMO, injections are better than feed through - and keep in mind that there are several "levels" of injectables that you can buy. For a long time, my old gelding was on 10cc of generic glucosamine injectable 1x/month. Then it moved up to 1x per week. Now we are on ICHON 1/month with every other week a dose of generic glucosamine. He is also on MSM, wich for his hips has helped Tremendously.
Good luck and keep us posted.