Acute suppurative arthritis is an acute inflammation of the joints caused by pyogenic bacteria. Hematogenous cases are more common in children, often affecting a single large limb joint, such as the hip, knee, or elbow. In cases of firearm injuries, the affected joint depends on the injury site, with the knee and elbow joints generally having a higher incidence.

bubble_chart Etiology

The causative bacteria of acute suppurative arthritis are mostly staphylococci, followed by streptococci. Gonococci and pneumococci are rare. Bacteria can invade the joint through hematogenous spread, trauma, or extension from adjacent infected lesions. Hematogenous infections may also be complications of acute fever, such as measles, scarlet fever, or pneumonia, and are more common in children. Traumatic cases are often due to open injuries, especially when the wound is not properly treated. Adjacent infections, such as acute suppurative osteomyelitis, can directly spread to the joint.

bubble_chart Pathogenesis

When bacteria invade a joint, synovitis occurs first, accompanied by joint effusion, swelling, and pain. As the condition progresses, the effusion changes from serous to serofibrinous and eventually becomes purulent. Once the joint is affected, the lesion gradually invades the cartilage and bone, ultimately leading to joint stiffness. After the joint becomes suppurative, it may rupture through the joint capsule and skin, forming a sinus, or spread to adjacent bone, causing suppurative osteomyelitis. Additionally, due to the laxity of the joint capsule and muscular rigidity, pathological dislocation may occur, resulting in joint deformity and loss of function.

In the acute phase of suppurative arthritis, the main symptoms are manifestations of toxicity. The patient suddenly experiences shivering and high fever, with severe systemic symptoms. In pediatric patients, high fever can lead to spasms. Locally, there are acute inflammatory manifestations such as redness, swelling, pain, and obvious tenderness. The joint fluid increases, causing fluctuation, which is more pronounced in superficial joints like the knee, resulting in a patellar floating sign. Patients often keep the knee joint in a semi-flexed position to relax the joint capsule and reduce tension. Prolonged flexion can lead to joint flexion contracture, with pain upon slight movement and protective muscular rigidity. If treated appropriately in the early stages, systemic and local symptoms gradually subside. If the joint surface is not damaged, full or partial joint function can be restored.

Diagnosis is primarily based on medical history, clinical symptoms, and signs. For patients suspected of having hematogenous suppurative arthritis, blood and joint fluid bacterial cultures and drug sensitivity tests should be performed. X-ray examinations are of limited help in the early stages, showing only joint swelling. Later, bone decalcification may occur, with joint space narrowing due to cartilage and bone destruction. In the advanced stage, joint bony or fibrous ankylosis and deformities may develop, accompanied by new bone proliferation, though sequestrum formation is rare.

Acute suppurative arthritis should be differentiated from acute suppurative osteomyelitis, wind-dampness arthritis, subcutaneous nodular arthritis, and rheumatoid arthritis.

The treatment principle is early diagnosis and timely, correct management to preserve life and limbs, and to maintain joint function as much as possible.

Systemic treatment is the same as for acute suppurative osteomyelitis. If it is a firearm injury, initial stage [first stage] surgical management should be performed to prevent joint infection.

Local treatment includes joint aspiration, immobilization of the affected limb, and surgical incision and drainage. For closed cases, joint fluid should be aspirated as much as possible. If the fluid is exudative or turbid, it should be rinsed with warm saline until clear, followed by antibiotic injection, performed once daily. If pus or post-traumatic infection is present, early incision and drainage should be performed, with the synovial membrane sutured to the skin edge. No drainage material should be placed in the joint cavity. The wound can also be managed with antibiotic drip drainage or local wet compresses to control infection as quickly as possible.

The affected limb should be appropriately immobilized or placed in traction to alleviate pain, prevent infection spread, maintain functional positioning, and prevent contracture deformities or correct existing ones. Once acute inflammation subsides or the wound heals, active and grade I passive joint movement should be initiated to restore joint mobility. However, activity should not begin too early or excessively to avoid symptom recurrence.

In summary, if treated promptly, the outcome is relatively favorable, especially in children, with good recovery of joint function.