Green lipped mussel powder can be beneficial for dogs primarily due to its anti-inflammatory properties and joint health benefits. The powder comes from mussels (Perna canaliculus) native to New Zealand and contains several key compounds: 
Omega-3 fatty acids which help reduce inflammation throughout the body;
Glucosamine and chondroitin, which support joint cartilage health;
Essential minerals like zinc, selenium, and magnesium;
Glycosaminoglycans (GAGs) that help maintain joint fluid.
Dogs experiencing arthritis, joint stiffness, or mobility issues may particularly benefit from this supplement. It can help:
- Reduce joint pain and inflammation 
- Improve mobility and flexibility
- Support cartilage repair and maintenance
- Potentially slow the progression of arthritis
However, it's important to note that individual dogs may respond differently to the supplement, and you should always consult with your veterinarian before adding it to your dog's diet, especially if your dog has any shellfish allergies or is on other medications.