Swelling of L knee; infection of the stryker knee/ left kneee replacement surgery; Joint infection; joint warmth; Orthostatic collapse; weak; Flu-like symptoms; fall; unable to walk; This spontaneous case was reported by a physician and describes the occurrence of ARTHRITIS INFECTIVE (infection of the stryker knee/ left kneee replacement surgery), SYNCOPE (Orthostatic collapse), ARTHRITIS INFECTIVE (Joint infection), ASTHENIA (weak), GAIT INABILITY (unable to walk), INFLUENZA LIKE ILLNESS (Flu-like symptoms), JOINT WARMTH (joint warmth), JOINT SWELLING (Swelling of L knee) and FALL (fall) in a 77-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 029A2114) for COVID-19 vaccination.    Co-suspect product included non-company product ADALIMUMAB (HUMIRA) injection for Rheumatoid arthritis.    The patient's past medical history included Knee replacement (left knee replacement.) in 2013. Concurrent medical conditions included Tobacco user (TOBACCO USER:30 TO 40 CIGARETTE STICKS A DAY) since 1962, Allergy to antibiotic (AMOXICILLIN DRUG ALLERGY MANIFESTED BY RASHES/HIVES), Abstains from alcohol, Diabetes, High cholesterol, Water retention and Blood pressure high. Concomitant products included INSULIN GLARGINE (LANTUS) and INSULIN ASPART (NOVOLOG) for Diabetes, SIMVASTATIN for High cholesterol, HYDROCHLOROTHIAZIDE for Hypertension and Water retention.   In September 2017, the patient started ADALIMUMAB (HUMIRA) (Subcutaneous) 40 mg once a week. On 10-Mar-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 15-Mar-2021, ADALIMUMAB (HUMIRA) (Subcutaneous) dosage was changed to 40 mg once a week. On 10-May-2021, ADALIMUMAB (HUMIRA) (Subcutaneous) dosage was changed to 40 mg once a week. In February 2021, the patient experienced FALL (fall) (seriousness criterion hospitalization). On 22-Feb-2021, the patient experienced ASTHENIA (weak) (seriousness criterion hospitalization) and INFLUENZA LIKE ILLNESS (Flu-like symptoms) (seriousness criterion hospitalization). On 23-Feb-2021, the patient experienced SYNCOPE (Orthostatic collapse) (seriousness criteria hospitalization and medically significant) and GAIT INABILITY (unable to walk) (seriousness criterion hospitalization). On 25-Feb-2021, the patient experienced JOINT WARMTH (joint warmth) (seriousness criterion hospitalization). On 17-Mar-2021, the patient experienced ARTHRITIS INFECTIVE (infection of the stryker knee/ left kneee replacement surgery) (seriousness criteria hospitalization and medically significant) and ARTHRITIS INFECTIVE (Joint infection) (seriousness criteria hospitalization and medically significant). On 25-Apr-2021, the patient experienced JOINT SWELLING (Swelling of L knee) (seriousness criterion hospitalization). The patient was hospitalized from 23-Feb-2021 to 25-Feb-2021 due to GAIT INABILITY. The patient was treated with AMOXICILLIN, CLAVULANIC ACID (AUGMENTINE [AMOXICILLIN;CLAVULANIC ACID]) at an unspecified dose and frequency. In February 2021, SYNCOPE (Orthostatic collapse), JOINT WARMTH (joint warmth) and FALL (fall) had resolved. In April 2021, GAIT INABILITY (unable to walk) and JOINT SWELLING (Swelling of L knee) had resolved. At the time of the report, ARTHRITIS INFECTIVE (infection of the stryker knee/ left kneee replacement surgery), ARTHRITIS INFECTIVE (Joint infection) and ASTHENIA (weak) was resolving and INFLUENZA LIKE ILLNESS (Flu-like symptoms) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 17-Mar-2021, Body fluid analysis: left knee infection (abnormal) Left Knee Infection. On an unknown date, Laboratory test: showed no stroke (normal) Showed no stroke.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Treatment for the events included un-specified intravenous fluids and unspecified intravenous medications during her hospital stay. Patient stated that On 23 Mar 2021, she had a Left knee replacement surgery due to the  infection of the Stryker knee. Laboratory test include fluid sample test which results in Left Knee Infection on 17-mar-2021. patient stated that her metal knee was replaced with a plastic knee patient went to rehabilitation on 02-apr-2021 and was discharged from rehabilitation care on 16-apr-2021.Patient stated that She was admitted for three days on 23 Feb 2021.On 02 Apr 2021, she  was discharged from hospital. On an unknown date, it was reported that the patient had an unspecified laboratory test; results were not provided.  Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded. However, multiple underlying co-morbidities may remain as confounding factors.   This case was linked to MOD-2021-234158 (Patient Link).; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded.However, multiple underlying co-morbidities may remain as confounding factors.