Acute infectious (septic) arthritis can be a manifestation of sepsis caused by bacteria, fungi or viruses, due to wound, postoperative, birth infection, criminal abortion, or if there is a focus in the internal organs. The disease-causing microorganism can almost always be isolated from intraarticular fluid, tissues and blood. Joint infection is often the result of hematogenous introduction of bacteria from a distant site of infection, less often direct infection penetrates into the joint with injuries, puncture wounds of the feet, acupuncture, repeated injections into the joint, etc.
The main causes of septic arthritis are staphylococcal, streptococcal, gonococcal infections, as well as gram-negative microorganisms (Escherichia coli, Proteus) and others. Acute infectious arthritis can occur against the background of furunculosis, tonsillitis, pneumonia, after cystoscopy, operations on the organs of the abdominal cavity and urogenital system etc. Diabetes mellitus, malignant neoplasms, RA and other diseases, chronic alcoholism predispose to the development of infectious arthritis.
Damage to the joint (in 80% of cases – monoarthritis) develops against the background of other symptoms of sepsis. The knee and hip joints are more often affected, less often – the shoulder, elbow, wrist, ankle.
Typically acute onset of arthritis, with sharp pains, fever, chills. The infected joint is sharply painful, reddened, hot and swollen, contains effusion, mobility and function are severely limited due to pain. In case of a hip joint infection, the pain can radiate to the front of the thigh or knee, and in the case of the sacroiliac joint infection, to the buttocks, lower back or the area of ​​the sciatic nerve. Multiple joint damage with septic arthritis is rare, patients with SLE receiving immunosuppressive drugs are more prone to it.

Arthritis caused by fungi and mycobacteria

Arthritis caused by fungi and mycobacteria , also usually monoarthritis, begins and proceeds more imperceptibly.
When examining synovial fluid, high cytosis (20-104 / ml) is detected with a predominance (up to 90%) of neutrophils. The liquid is cloudy, its viscosity is reduced, the mucin clot is friable. X-ray diffraction of the capsule and edema of the periarticular tissues are noted, epiphyseal osteoporosis, narrowing of the joint gap, subchondral erosion are detected very early, and with inadequate treatment, rapid destruction of the cartilage and bone.
The outcome of the disease may be secondary deforming osteoarthrosis or bone ankylosis of the joint.
The possibility of an infectious etiology of arthritis should be assumed in all cases of acute mono- and oligoarthritis. The diagnosis is confirmed by examining synovial fluid – viewing smears stained by Gram, isolating the culture of microorganisms.
With septic arthritis, antimicrobials are used and adequate joint cavity drainage is performed. The sooner treatment is started, the more likely it is to maintain joint function, therefore antibiotic therapy is started until the results of inoculation of synovial fluid are obtained. After identification of the pathogen, treatment may be revised if necessary. Antibiotics that easily penetrate the joint from the blood are administered parenterally. Intra-articular administration of antibiotics is not necessary and may cause irritation of the synovial membrane. For streptococcal and staphylococcal infections, penicillin is used at 250 000 units / kg per day, on average for adults 12–20 million units intravenously, distributing the dose for 4 administrations, or 60–100 mg / kg zeporin per day in 2–3 doses. Treatment is carried out for 3-6 weeks.
In gram-negative flora, a combination of aminoglycoside (e.g. gentamicin) with a broad-spectrum antibiotic (penicillin series, cephalosporin) is recommended.
Shown daily or every other day the drainage of the joint cavity, with aspiration of pus, which allows you to save articular cartilage. It is necessary to ensure rest of the limb to reduce pain and inflammation, sometimes it is immobilized with a tire. Passive exercises can be started a few days after the start of treatment, and active ones – after the inflammation subsides, the joint load is prohibited until the symptoms of active inflammation disappear completely.
The course of treatment is 1 – 1.5 months.
With insufficiently effective treatment, the disease takes a long course with the formation of persistent joint configuration and limitation of mobility.

Gonococcal arthritis

Gonococcal arthritis is one of the options for septic arthritis. It develops in patients with acute and chronic gonorrhea with hematogenous spread of infection from the genitourinary tract. It is more common in young women, which often has an asymptomatic course of the disease, as well as menstruation and pregnancy-contributing bacteremia. In the development of gonococcal arthritis, 2 phases are distinguished – a short (2–4 days) “bacteremic” characterized by fever, chills, migratory arthralgia, and a long “septic” lesion of one or two joints (usually knee, ankle, elbow, wrist). Inflammation of the calcaneal tendon, as well as damage to the ankle joints with the development of the so-called “flat gonorrheal foot” is considered characteristic of gonococcal infection. The latter is associated with the spread of infection from the ankle joint to the metatarsal and tarsal joints, with simultaneous atrophy of the muscles of the foot and lower leg and the development of flat feet. The outcome of gonococcal arthritis, as a rule, is secondary deforming osteoarthrosis. The diagnosis of the disease is confirmed by positive blood culture, the detection of gonococcus in the synovial fluid or specific skin manifestations of the infection – papules on a red base, usually filled with purulent contents with necrosis in the center and localized on the back, distal extremities or around the joints. Differential diagnosis of gonococcal arthritis should primarily be carried out with arthritis in Reiter’s syndrome. With gonococcal arthritis, massive doses of antibiotics are effective. You can use the following combination of drugs: penicillin intravenously at 10 million units per day to reduce the clinical manifestations of arthritis, then ampicillin 2.0 g for 7-10 days or high doses of penicillin intravenously or intramuscularly for 3 days, then ampicillin 3.5 g day for 7 days. Recommended repeated daily aspiration of synovial fluid and the appointment of non-steroidal anti-inflammatory drugs. Osteoarticular tuberculosis is one of the frequent extrapulmonary forms of tuberculosis. There are tuberculous arthritis, spinal tuberculosis (Pott’s disease) and Ponce arthritis.