
When our breed have been used as working gundogs and begin to go lame because of injury they are usually retired, as any excessive strain on the joints results in lameness. It is usually osteo-arthritis through wear and tear, the same as us humans. However, the majority of the working gundogs do not develop this until in their later years, so in a relatively young dog it needs, in the first instance, to be checked out by a vet - this costs money, they may well give him a steroid injection to reduce any swelling and inflammation. It could be also a chipped bone on the elbow which floats around in the joint space, or inflammation of the synovial fluid in the joint, lots of reasons for lameness, it really needs to be seen by a professional.
The dog in question also needs complete rest, no free exercise, lead only for at least 6 weeks.