The knee was scraped and has formed a scab, but there is pus underneath. What could be the cause, and what should be done?

The knee has developed a scab after an injury, but there is pus underneath, which is generally caused by bacterial infection, suppurative infection, or worsening joint inflammation. Appropriate treatment methods can be selected based on the specific cause. The detailed analysis is as follows:

1. Bacterial Infection

If improper local care after a knee injury leads to bacterial infection and results in pus beneath the scab, follow medical advice to promptly clean and disinfect the wound using physiological saline, iodophor, hydrogen peroxide, or similar agents.

2. Suppurative Infection

If incomplete treatment of the injured knee leads to suppurative infection, follow medical guidance to clean the wound and apply antibiotic ointments such as azithromycin ointment, roxithromycin ointment, or levofloxacin ointment to reduce infection.

3. Worsening Joint Inflammation

If joint damage occurred during the knee injury, resulting in intra-articular inflammation and pus formation, follow medical advice to use medications such as ibuprofen sustained-release capsules, aspirin enteric-coated tablets, or diclofenac sodium sustained-release tablets to eliminate local inflammation and relieve pain.

In addition, this condition may also result from trauma or immune system deficiencies. Patients are advised to actively cooperate with doctors for treatment, properly care for the wound, and avoid re-infection, which could impair wound healing.