Septic Arthritis; Synovitis; early-stage adhesive capsulitis versus rotator cuff; high-grade articular-sided tear of the supraspinatus/deep fissure was noted between the junction of the supraspinatus and infraspinatus tendon insertion on the articular side; Anterior shoulder pain; Tightness at the end of motion; a large joint effusion with debris; a large joint effusion with debris; prominent subcortical cystic changes of the posterolateral humeral head; significant intraarticular edema; long head of the biceps (LHB) tendon was erythematous; long head of the biceps (LHB) tendon was erythematous, thickened, and very scarred to the rotator interval; tendon thickened; Muscle weakness; Fatigue; Weakness; Improper administration technique; This case was reported in a literature article and described the occurrence of septic arthritis in a 32-year-old female patient who received Flu unspecified (Influenza vaccine) for prophylaxis.   The patient's past medical history included clostridium difficile infection (5 year prior).   On an unknown date, the patient received Influenza vaccine at an unknown dose. On an unknown date, 14 days after receiving Influenza vaccine, the patient experienced septic arthritis (serious criteria GSK medically significant), synovitis (serious criteria clinically significant/intervention required), adhesive capsulitis, rotator cuff tear, shoulder pain, muscle tightness, joint effusion, bone shedding debris, subchondral bone cyst, swollen joints, erythema, scar, tendon thickening, muscle weakness, fatigue, weakness and wrong technique in drug usage process. The patient was treated with paracetamol (Acetaminophen), ibuprofen, vancomycin and metronidazole. On an unknown date, the outcome of the septic arthritis, synovitis, adhesive capsulitis, rotator cuff tear, muscle tightness, joint effusion, bone shedding debris, subchondral bone cyst, swollen joints, erythema, scar, tendon thickening, muscle weakness and wrong technique in drug usage process were unknown and the outcome of the shoulder pain was recovered/resolved and the outcome of the fatigue and weakness were not recovered/not resolved.   The reporter considered the septic arthritis, synovitis, adhesive capsulitis, rotator cuff tear, shoulder pain, muscle tightness, joint effusion, bone shedding debris, subchondral bone cyst, swollen joints, erythema, scar, tendon thickening, muscle weakness, fatigue and weakness to be related to Influenza vaccine.  Additional information provided as follows: This case was reported in a literature article and described the occurrence septic arthritis of the glenohumeral joint in a 32-years-old female patient who was vaccinated with unspecified influenza vaccine (manufacturer unknown) for prophylaxis.  The patient was healthy woman with an intact immune system. She had no ongoing infections or risk factors for a joint infection. There was no previous trauma or procedure to the affected shoulder. The patient was right-hand-dominant, and she works as nurse in pediatric intensive care unit. She had a history of C. difficile infection 5 yr prior. The patient had no other medical comorbidities. No information on patient's family history or concomitant condition was provided. On unspecified date, the patient had received unspecified influenza vaccine (administration route and site unspecified, dosage unknown; batch number not provided). The age of vaccination was not provided. On an unspecified date, 2 weeks after vaccination, the patient presented with the acute onset of left shoulder pain. She complained of moderate anterior shoulder pain, which was deep within the joint. On examination, there was no atrophy, skin changes, or crepitus present. On range of motion testing, she had 70 degrees of external rotation (ER), 160 degrees of forward elevation (FE), and reached to T7 on internal rotation (IR), which was equal to the contralateral side. However, there was pain at end-point of range of motion that was only present on the left. The patient described subjective tightness at the end of motion. Strength was normal and symmetric. On further testing, Hawkins', Speed's, and O'Brien's tests were positive. Radiographs showed no osseous abnormalities. Potential diagnosis at that time included early-stage adhesive capsulitis versus rotator cuff. The patient returned to the office 1 month later with continued pain, requiring ibuprofen and acetaminophen. Repeat range of motion testing showed 70 degrees of ER, 160 degrees of FE, and L3 on IR. Strength was still normal. No constitutional symptoms were reported. Conservative management was continued. A 3 months after her original presentation, the patient's symptoms were not improving. Her physical examination had not changed since the previous office visit. An magnetic resonance imaging. (MRI) was obtained and showed a high-grade articular-sided tear of the supraspinatus, prominent subcortical cystic changes of the posterolateral humeral head, and a large joint effusion with debris and synovitis (i.e 3 month after initial presentation showing significant intraarticular edema and cystic cortical changes in the coronal). The decision was made to proceed with surgery as the degree of synovitis was worrisome. Intraoperatively, a fibrous quality of the joint fluid was noted, but there was no purulence. The thickened joint fluid was collected and sent for cell count, crystals, Gram stain, and cultures. Upon initial visualization of the joint, a synovitic reaction was seen; the synovium was inflamed and adherent to the capsule throughout the entire shoulder. The synovitis was debrided and sent for pathology, aerobic, and anaerobic cultures. A thorough incision and drainage was performed. A deep fissure was noted between the junction of the supraspinatus and infraspinatus tendon insertion on the articular side. This was repaired with a side-to-side suture of prolene, which was tied on the bursal side. The long head of the biceps (LHB) tendon was erythematous, thickened, and very scarred to the rotator interval. To eliminate persistent biceps pain, a subpectoral tenodesis was performed, tenodesing the LHB to the pectoralis major with prolene suture. Surgical pathology showed polypoid fragments of synovium and fibrovascular tissues with active chronic inflammation and focal fibrinopurulent exudate. Gram stain of the fluid collected showed gram-positive cocci, but cultures were negative. A peripherally inserted central catheter (PICC) line was placed, and the patient was started on empiric therapy with vancomycin. The patient was seen at 2 weeks postoperatively and reported moderate pain. The incisions were well healed with no signs of infection. Physical therapy was started at that time. At 5 weeks postoperatively, her pain was improving. Range of motion of the affected shoulder was 40 degrees of ER, 140 degrees of FE, and internal rotation was not tested. At 6 weeks postoperatively, the patient complained of diarrhea. Due to the history of Clostridioides difficile infection. A stool assay for Clostridioides difficile toxin was positive, and she was started on a 10-day course of metronidazole. Vancomycin was stopped, and the PICC was removed after completion of 6 weeks of antibiotics. 3 months postoperatively, her pain was adequately controlled without the need for medication. Range of motion was 60 degrees of ER, 160 degrees of FE, and internal rotation to L3 with mild weakness in FE on the left. She returned to work as a nurse at this time, with a 10-pound lifting restriction. The patient returned for follow-up at 7 month postoperatively. There was still some lingering pain and tightness. Range of motion was 65 degrees ER, 160 degrees FE, T12 for IR and 60 degrees of internal rotation at 90 degrees of abduction. At that time, an radiograph showed two subtle areas of lucency (i.e Two subtle lucencies were seen within the humeral head at 7 month postoperatively). An MRI was obtained to rule-out subclinical infection, which showed no ominous signs, including interval resolution of edema and an intact rotator cuff (i.e At 7 month, a coronal cut of postoperative MRI shows interval resolution of infection and an intact supraspinatus tendon). She was seen in clinic at 14 month postoperatively. At this time, she felt some weakness and fatigue, but did not experience rest pain. She continued to work full-time without restrictions. On examination range of motion was 70 degrees of ER, 170 degrees of FE, and to T12 on IR. Her strength was 5/5 with ER, 5-/5 with FE, and 5/5 with IR. The patient was satisfied with her progression and was followed on an as-needed basis after this point. The author commented, "Her pain started soon after the injection and never resolved prior to presentation. Due to a lack of another cause and the time course in which her symptoms began, we believe that the vaccine caused an indolent infection. There were no findings on physical examination that were suggestive of an infection on initial presentation. A positive Gram stain is a unique finding from what has been previously reported in the literature. The rotator cuff tear seen in our 32-year-old patient was likely due to the infection and not a chronic degenerative tear. The prolonged course of antibiotic treatment and C. difficile makes for a more severe case than previously reported." The author concluded "We describe an indolent infection and rotator cuff tear caused by improper administration technique for an influenza vaccine and the resulting complications. The health benefits of vaccines vastly outweigh the risks associated with them, but they are not completely without risk. It is our goal to help recognize these rare but potentially severe complications early. Additional research in this area may help us to better understand the prevalence of vaccine induced shoulder injuries and the exact etiology of rotator cuff tears in the setting of infection". The article corresponding to this case is not available for submission due to copyright restriction.      Lab Comments: On an unspecified date, lab test were done.  Hawkin's, Speed's, and O'Brien's tests were positive. Radiographs showed no osseous abnormalities. On examination, there was no atrophy, skin changes, or crepitus present. On range of motion testing, she had 70 degrees of external rotation (ER), 160 degrees of forward elevation (FE), and reached to T7 on internal rotation (IR), which was equal to the contralateral side. However, there was pain at end-point of range of motion that was only present on the left. Repeat range of motion testing showed 70 degrees of ER, 160 degrees of FE, and L3 on IR. Strength was still normal. Her physical examination had not changed since the previous office visit. A magnetic resonance imaging (MRI) was obtained and showed a high-grade articular-sided tear of the supraspinatus, prominent subcortical cystic changes of the posterolateral humeral head, and a large joint effusion with debris and synovitis (i.e 3 month after initial presentation showing significant intraarticular edema and cystic cortical changes in the coronal). Intraoperatively, a fibrous quality of the joint fluid was noted, but there was no purulence. The thickened joint fluid was collected and sent for cell count, crystals, Gram stain, and cultures. Upon initial visualization of the joint, a synovitic reaction was seen; the synovium was inflamed and adherent to the capsule throughout the entire shoulder. The synovitis was debrided and sent for pathology, aerobic, and anaerobic cultures. The long head of the biceps (LHB) tendon was erythematous, thickened, and very scarred to the rotator interval. Surgical pathology showed polypoid fragments of synovium and fibrovascular tissues with active chronic inflammation and focal fibrinopurulent exudate. Gram stain of the fluid collected showed gram-positive cocci, but cultures were negative.