Urgent considerations
See Differentials for more details
Septic nongonococcal arthritis
By far the most serious cause of an inflamed joint. Patients at risk include:[36][37]
Older people
Intravenous drug users
Those with recent bacteremia
People with diabetes
Immunocompromised patients (e.g., those with HIV disease, on immunosuppressive agents, or with other immunocompromised states)
Patients with sickle cell disease or other hemoglobinopathies
People with rheumatoid arthritis
Those with prosthetic joints
Those who have had recent arthroscopy or arthrocentesis.
If the diagnosis is missed and treatment with appropriate antibiotics is not instituted early, septic nongonococcal arthritis can lead to permanent joint damage and be life-threatening.
Definitive diagnosis of a septic joint requires joint aspiration and synovial fluid analysis (including Gram stain and culture). In all patients with suspected joint sepsis, empiric antibiotic therapy should be started once appropriate specimens (i.e., blood and synovial fluid) have been obtained for culture.[38] Empiric antibiotic coverage must include coverage for Staphylococcus aureus (including MRSA), Streptococcus pyogenes, and Gram negative and anerobic bacteria in vulnerable patients.
Antibiotics are often given intravenously for 2 weeks, followed by a further 4-6 weeks of oral therapy. Prosthetic joint infections are treated more aggressively and often warrant removal of the prosthesis, treating aggressive antibiotic treatment, and eventually replacing the old prosthesis with a new prosthesis one once the infection has been eradicated.
Gonococcal arthritis
Gonococcal arthritis is a manifestation of disseminated gonococcal infection (DGI). DGI is much more common in women, especially during the perimenstrual period, due to endometrial disruption enabling Neisseria gonorrhoeae to enter the bloodstream. Patients present initially with polyarthralgia, tenosynovitis (typically of the wrists and/or ankles), and sparse, painful vesiculopustular skin lesions. Later, the condition presents as mono- or oligoarthritis (involving <5 joints).
Diagnosis can be established by Gram stain and culture of urethral, cervical, rectal, or oropharyngeal swabs or by DNA probe of fluid from the affected joint. Skin pustules can also be cultured, though the yield is very low. Concomitant infection with Chlamydia trachomatis, syphilis, and HIV is frequent and should be tested for. Bacteremia and arthritis should be treated with ceftriaxone or similar antibiotics, depending on local policy and sensitivities.
Indolent infections
Tuberculous, nontuberculous mycobacterial, brucellar, and fungal arthritides are much less common than acute pyogenic (septic) arthritis or gonococcal arthritis, and are often indolent. A high index of suspicion is necessary, and it is often difficult to establish the correct diagnosis. Some radiologic clues can suggest tuberculous arthritis, such as juxta-articular osteopenia, peripheral bone erosions, and gradual narrowing of the joint space (Phemister triad). Synovial biopsy and culture in special media are necessary if joint aspiration does not provide a definitive diagnosis. If the diagnosis is missed or the wrong treatment is instituted, permanent joint damage can occur, and the disease can disseminate and become life-threatening. Antibiotics and antifungal agents, specific for the causative organism, are often given for 6 to 18 months. Open joint drainage and debridement may be necessary if an abscess develops.
Joint trauma
In a patient with a recent history of joint trauma, pain and swelling of the involved joint always raises the possibility of a fracture, dislocation, internal derangement, traumatic effusion, or hemarthrosis. On occasion (e.g., with drug overdose, alcohol intoxication, or a history of seizure or concussion), the history of joint injury may not be available; hence, if there is any suspicion of trauma to a joint, immobilization and appropriate imaging studies are necessary to rule out a fracture or other anatomic derangement.
Acute hemarthrosis
This condition should be considered particularly in:
Patients with a known history of a bleeding disorder (e.g., hemophilia A or B, or acquired factor VIII inhibitor)
Patients on anticoagulation
People with a history of recent injury to the affected joint (e.g., torn cruciate ligament).
Arthrocentesis reveals blood in the synovial cavity, which triggers an intense inflammatory reaction. If therapeutic arthrocentesis (sometimes repeated) is not done promptly, lysosomal enzymes liberated from inflammatory cells can destroy cartilage and cause permanent joint damage. Further investigations such as plain x-rays and magnetic resonance imaging of the affected joint may be required if there is suspected trauma to a joint.
Intra-articular metastatic cancer
Although extremely rare, metastasis may be the first manifestation of a malignancy in which the primary source is unknown. A high index of suspicion is necessary in patients with a known malignancy. Conservation of joint function may be achieved through minimally invasive surgery.
Synovial sarcoma
This rare malignancy affects young adults, with a median age of 35 years at the time of diagnosis. The lower-extremity joints are the most commonly affected sites. With early diagnosis, cure can be achieved in patients with localized disease; however, missed diagnosis can lead to local joint destruction and incurable metastatic disease. The most common treatment is surgery to remove the entire tumor with negative margins (i.e., no cancer cells are found at the edge or border of the tissue removed during surgery). If the first surgery does not obtain negative tissue margins, a second surgery may be needed.[39]
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