The World Health Organization has reported more than 6.38 million deaths related to the COVID-19 pandemic ^[1]. The disease can appear with numerous atypical/uncommon clinical manifestations that can lead to late diagnosis and remain a challenge for the clinician. Various systems, including the musculoskeletal, can be affected and the complications can either settle early or last for a longer period or even become permanent. There is strong correlation between the different variants and the clinical presentation ^[2]. Crucial role to the clinical presentation of the COVID-19 demonstrates the variant that every time is responsible for the disease. Predominant musculoskeletal symptoms include arthralgia and myalgia. There is also established evidence that the virus can either trigger undiagnosed rheumatologic conditions or be responsible for the exacerbation of a previously controlled disease. Arthralgia is a well-reported side effect of COVID-19 vaccine [3, 4, 5]. The current paper presents the case of a young patient, without background of rheumatologic disease or any comorbidities, with acute, severe onset of hip pain which started only shortly after being tested positive for COVID-19. The diagnostic approach, management, and follow-up are presented followed by a literature review.

We present the case of a 20-year-old white female patient, previously fit and healthy with sudden onset of left hip pain. Symptoms started a day before presentation to accident and emergency and 9 days after tested positive for COVID-19. The pain progressively deteriorated and at presentation was unable to weight bear. On assessment, the left hip joint was in 15° of flexion and 20° of external rotation. The area was not warm to the touch and there was no erythema. On palpation and leg roll, the groin was significantly tender and the patient was unable to straight leg raise. There was no focal neurology and the perfusion of the leg was normal. The patient denied any history of trauma. Nasopharyngeal swabs at admission were performed and the PCR test was positive for SARS-CoV-2. She was entirely asymptomatic from the COVID infection point of view. Her past medical history included an uneventful resection of endometriosis 3 months ago. The general surgeons and the gynecologists reviewed the patient and excluded any sinister pathology. From her past medical history, there were no history of injury and no operation of the hip or rheumatic diseases. Moreover, she mentioned history of endometriosis and resection in November of 2021. The patient is non-smoker, she does not receive any medication, and no allergies mentioned. A diagnostic aspiration under sedation in theatres was offered. 8 mL yellowish fluid was aspirated and two sample pots were used and sent for MC and S. The culture was negative for infection. Post-aspiration, there was not any improvement in the symptoms, so an open incision, drainage, and washout were the next step forward. Further investigations requested by the rheumatologists ruled out juvenile arthritis. The following days, the pain, range of movement of the hip joint, and mobility significantly improved. For the first 2 weeks, partial weight bearing was suggested and the period after she was allowed to weight bear as tolerated. The markers for infection returned within normal range. In the final 6-month follow-up, the patient was symptom free and the blood markers for infection remained normal. She is now discharged having full mobility and returned to her normal activities.

The SARS-CoV-2 virus infection is expressed predominantly by respiratory complications, however, can also be responsible for extra-pulmonary symptoms ^[6]. More than 570 cases have been reported since the outbreak of the pandemic and the continuously raising number causes uncertainty regarding the long-term complications ^[1]. The complications from the musculoskeletal system may require medical attention and the severity can require some form of intervention. Immunocompromised patients and those suffering from autoimmune disease are considered more vulnerable when exposed to the virus and can suffer more severe complications. Despite the large number of cases reported globally, only 9 cases of acute monoarthritis in which there is no history of other rheumatic diseases have been reported in the literature. Among those cases, there is not a single case that involves pathology of the hip joint [6, 7, 8, 9]. Therefore, the case presented in the current paper is the first COVID-19-related acute monoarthritis, reported worldwide. We found the case of a young, fit, and healthy female patient presented in this study, a diagnostic challenge and we would like to share the management that can be of exceptional value to the clinicians that can come across similar situations. Those patients with sudden presentation of monoarthritis should be screened routinely for COVID-19 infection. An updated diagnostic algorithm for acute monoarthritis, taking under consideration, the SARS-CoV-2 virus would lead to earlier diagnosis, more efficient planning of the treatment and would reduce the morbidity and the length of stay in the hospital and therefore minimizing the cost of care providing by the health-care systems. Our experience showed that after the open irrigation of the joint, the symptoms immediately settled and the patient very soon reported excellent recovery and returned her daily activities. Regarding management, comparing to the other reported cases which have been treated conservatively with IV antibiotics, our approach was surgical with open wash out. Both treatment plans have good outcomes and the patients returned back to their daily activities. However, surgical management seems to help symptoms settle quicker as from the 1^st post-operative day, there was a significant improvement of the symptoms and reduced the duration of hospitalization.

Viral-related arthritis remains a diagnosis of exclusion and underlines the importance to perform all the tests to rule out the possibility of serum negative arthritis. Negative joint fluid cultures and negative rheumatologic screening (rheumatoid factor, antinuclear antibody, anti-citrullinated protein antibody, and HLA-B27) are essential ^[10]. This case argued that clinical suspicion is the key of the early diagnosis and treatment for every COVID-19-positive patient with musculoskeletal symptoms, even for the patients with no history of autoimmune diseases.

Clinical suspicion and expansion of the differential diagnosis are the keys to diagnose the cause of arthritis to patients without predisposing factors. MDT is a crucial necessity for treatment and diagnosis in additional to surgical intervention.