In the US, there are several options currently available. I use the acronym WEDS to remember them.

W: Weight. Dogs on the thin side have healthier joints. It is important to maintain muscle tone but have very little fat.
E: Exercise. Dogs with joint trouble should get at least 30 minutes per day of low-impact exercise. Physical therapy can also be performed. We work with partners to provide PT.
D: Diet and drugs.

Fish oil. Omega-3 fatty acids from fish oil have been shown in controlled studies to be effective. Welactin is a great option for this.
NSAIDs. Non-steroidal anti-inflammatory drugs can be prescribed that are generally safe and can make a big difference in joint pain and the progression of joint disease. We carry several different NSAIDs including a high-tech prostaglandin receptor antagonist, which is safer than traditional cox-inhibitor NSAIDs.
Injectable polysulfated glycosaminoglycans. This is sort of a "nutriceutical" that is injected and can help restore the joint fluid. We carry this treatment.
Intra-articular hyaluronan. These injections lubricate the joint and can protect the remaining cartilage. We refer to surgeons for this service.

S: Surgery. In some cases, surgery is an option to alleviate pain.

There are other procedures that are being evaluated such as cold laser therapy, shockwave therapy, ultrasound therapy and acupuncture. The jury is still out on these therapies.

Some supplements have less evidence but we hear positive things from our clients: Glucosamine, chondroitin sulfate, green-lipped mussel extract, to name a few. We carry veterinary products that provide these.