What is Inflammatory joint disease (arthropathy)?
Inflammatory joint diease is where high levels of acute inflammatory cells invade the joint. There are two classic causes
- Septic arthritis (infective arthritis, suppurative arthritis) is a joint infection caused by bacterial organisms.
- Immune-mediated polyarthritis is a non-infectious joint disease.
Septic arthritis may be due to haematogenous (in the blood) spread of infection from respiratory, digestive, urinary, umbilical, or heart valve infections. However, more often it is caused by direct bacterial inoculation of joints from penetrating trauma, surgical procedures, or intra-articular injections.
Immune-mediated arthropathies can be related to other conditions within the body such as gastroitesinal disease, infection elsewhere in the body and occasionally related to cancer. However, in most cases there is no identifiable cause. Other conditions such as septic arthritis, rickettsial arthritis, rheumatoid arthritis, osteoarthritis all require exclusion.
Septic arthritis can be found in any aged dog, but males of larger breeds are more commonly affected. Infection may be seen without any cause in very young dogs and in older dogs with pre-existing osteoarthritis. A penetrating injury into the joint or surgery can also cause infection to occur.
Lameness may be very severe or non-weight-bearing on the affected limb. The affected joint may be swollen, painful and warm, drain purulent (pus) material and have reduced range of motion. Some dogs may have a fever. The signs may be subtle (only lameness and joint swelling) with chronic infections.
Immune-mediated arthritis/polyarthritis can affect all breeds and ages of dogs. Some studies have suggested German Shepherds, Doberman Pinschers, Collies, Spaniels, Retrievers, Terriers, and Poodles are more predisposed. Females are more commonly affected. Affected pets usually show signs of stiffness, difficulty rising, fever, reduced appetite or lethargy. More than one joint is usually involved but single-limb lameness can be seen. Affected animals may or may not have difficulty rising and walking. Some animals have a chronic fever of unknown origin. The joint may be painful, swollen or have reduced of range of motion. Other systems such as the kidneys, skin and eyes may be affected.
Radiographs can look similar in the early course of both diseases. Synovial (joint fluid) analysis is the best means of diagnosing both septic and immune-mediated inflammatory joint disease.
Diagnosis of inflammation within the joint is confirmed when joint fluid is extracted from the joint with a needle. Increased cell numbers are seen within the joint. Fluid may need to be submitted to the laboratory for further assessment under the microscope and possibly for bacterial culturing.
Antibiotics are generally administered for 4-6 weeks and for at least 1-2 weeks after clinical signs have resolved. Antibiotics are chosen based on the type of bacteria found on culture. Anti-inflammatory medications are often necessary to alleviate pain in affected joints.
Joint exploration, including debridement and lavage (flushing) is indicated for postoperative joint infections, septic joints for which treatment was delayed, joints that have not responded to appropriate medical therapy and penetrating joint wounds.
Treatment often includes steroids with the inclusion of other immune-modulating agents for more persistent cases. These medicines act to reduce the formation of immune complexes and the subsequent inflammatory response. These cases may need to see a specialist in Internal Medicine to assess for underlying disease.