I'm hearing that excessive pulling causes strain on the knee joint and damages the patella. There is a harness available that rides under the "arms" and when the dog pulls it doesn't injure the dog, but it is uncomfortable enough to stop the pulling. It's called the Sporn anti-pull harness: Perhaps it will help. I used it on a very strong ACD and it worked like a charm.Also, I use Maya's idea of placing the collar in the show position when AJ is having trouble with distractions. He doesn't have any choice but to not pull.
Small Sporn Mesh Anti Pull Harness, Black - Captivating Canines
The Yuppie Puppy Mesh Anti-pull Dog Harness uses the patented Sporn Sherpa Sleeve to prevent skin abrasion and the accompanying canine discomfort. An excellent training aid to break the habit of pulling quickly and easily, this flexes with the dog as the animal walks. As a walking harness, buyers should not use it as a car harness or to tie the animal outside. It comes in four sizes, ranging from toy, which is suitable for dogs up to 10 lbs, to XL for dogs weighing between 50 and 100 lbs. Whatever the size of the dog, the Yuppie Puppy mesh dog harness can help any owner train their animal.
Sporn Mesh Anti Pull Harness, Black - Nextag
Make walking your furry friend painless and stress free with the Sporn Mesh Anti-Pull Dog Harness. This one piece harness is specially designed to humanely deter dogs from pulling on their leads during walks. As the dog pulls on its lead, the padded restraints underneath the dog's front armpits gently elicit an undesirable tickle effect on the dog's brachial plexus that deters from further pulling. This is called the breaking mechanism. If the dog is not pulling on the lead, the breaking mechanism is not in effect. The harness safely draws back around the dog's chest and withers areas only, and places no strain on the dog's neck. All materials and components are made from durable, high quality nylon webbing and nickel-plated hardware to reduce weathering. With the flexible mesh chest pad and thickly padded Sherpa sleeves, it is sure to provide maximum comfort and control for your dog.
Available in three sizes: Small, Medium and Large/X-Large.
Color choices: Black, Red or Blue.
Sporn Mesh Anti Pull Harness, Black