Cavernous Hemangioma of the Knee, Causing Pain Following a Fall in a 5-Year-Old Girl: a Case Report

Cavernous hemangioma, an uncommon benign vascular lesion, can affect different joints. It generally presents as atraumatic swelling over the joint with normal radiographic findings. We present a case of a healthy 5-year-old girl with chronic knee pain over the anteromedial aspect following minor trauma. The patient underwent all baseline blood investigations and plain radiograph of her knee, all of which were normal. Magnetic resonance imaging showed hemangioma. Surgical excision was performed and histological studies confirmed a cavernous hemangioma. Delayed diagnosis may increase the risk of invading and damaging the joint resulting in further morbidities.


Introduction
Hemangioma is a common benign vascular lesion that commonly affects different pediatric age groups and accounts for 7-10% of all soft tissue tumors [1]. These soft tissue lesions can be described based on the site of origin as cutaneous, subcutaneous, intramuscular, synovial, or sub synovial [2].
Synovial hemangioma most commonly affects the knee but can affect different joints [3]. It may involve the entire joint or only part of it and can be juxta-articular (just superficial to the joint capsule), intra-articular, or intermediate [4]. Histologically, the most common type of hemangioma is cavernous in origin and accounts up to 50% of cases [1].
Cavernous hemangioma is characterized by large, dilated blood vessels and blood-filled space lined by flattened endothelium [5]. Herein, we discuss the presentation, diagnosis, and management of cavernous hemangioma of the knee.

Case Report
A healthy 5-year-old girl was referred to the pediatric orthopedic clinic from the pediatric primary care, complaining of right knee pain and swelling for 1 month prior after a fall. The mother did not seek any medical advice prior to that. The growth parameters were normal. The physician ordered an X-ray of the knee, which showed no obvious pathology. Basic laboratory investigations were ordered by the physician, and the results were normal. The patient was then referred to the pediatric orthopedic clinic.
The patient came to our clinic 6 months after visiting pediatric primary care. She was a full term spontaneous vaginal delivery and had normal course post-delivery. She is the family's 3rd child and was up-to-date with her vaccinations. The pain increased with walking and decreased with rest and analgesia. Pain began after a minor fall 7 months prior. The mother denied any constitutional symptoms. Clinical assessment showed swelling over the anterior medial aspect of the right knee with no change of color, but it was tender to the touch. The patient had full range of motion, and the knee was stable. Examination showed that the distal neurovascular structures were intact.
Regarding radiologic investigations, anteroposterior and lateral radiographs of the left knee showed swelling of the soft tissue over the medial aspect ( Fig. 1). An ultrasound of the knee showed findings that could be related to organized hematoma, but a soft tissue neoplastic lesion This article is part of the Topical Collection on Surgery could not be ruled out as increased vascularity was more pronounced than expected in resolving hematoma. Therefore, magnetic resonance imaging (MRI) of the right knee was performed and showed a 2.6 × 2.6 × 1.6 cm (CC × lateral × AP diameters) lobulated irregular enhancing hypervascular mass located anteromedial to the right knee, abutting and potentially invading the fibers of the medial patellar retinaculum with no obvious intra-articular extension (Figs. 2 and 3).
After consulting the musculoskeletal radiologist, hemangioma was suspected. The risks and benefits of surgical excision were explained to the parents, and they consented to surgical intervention. The patient underwent surgical excision of the soft tissue mass utilizing anteromedial incision over the mass. The mass was carefully and thoroughly excised; it measured 2.5 × 2.0 × 0.7 cm (Fig. 4). It was localized over the surface of the patellar reticulum with in invasion into it. No involvement of the joint and it was not involving the muscle or neurovascular structures. The excised soft tissue mass was sent for histopathological examination and microbial culture. Histopathological examination confirmed the diagnosis as cavernous hemangioma.
Patient was seen 2 weeks after the surgery, 6 weeks and the final follow up was 9 months. Patient was doing fine with no complain or complication.

Discussion
Bouchut first described synovial hemangioma in 1856 [6]. Cavernous hemangioma is a congenital vascular lesion with a familial occurrence [7]. The clinical presentation varies Fig. 1 Anteroposterior radiographs of the right knee shadowing over the medial aspect of the image Fig. 2 Axial cut magnetic resonance imaging scans taken prior to the surgical excision. The soft tissue mass is noted anteromedial to the right knee, invading the fibers of the medial patellar retinaculum with no obvious intra-articular extension Fig. 3 Sagittal cut magnetic resonance imaging scans taken prior to the surgical excision. The soft tissue mass is noted anteromedial to the right knee, invading the fibers of the medial patellar retinaculum with no obvious intra-articular extension widely, ranging from painless tumors at presentation to ones that may cause mechanical irritation over the knee as a result of recurrent intra-articular bleeding, hemorrhagic synovitis, and arthropathy [8]. Cavernous hemangioma generally affects children below the age of 16 and occurs more often in females [9,10]. As stated previously, cavernous hemangioma can be intra-capsular (intra-articular) or extracapsular (juxta-articular). Patients with juxta-articular cavernous hemangiomas are generally diagnosed at a late stage [8]. The hallmark presentation is atraumatic painful bloody knee effusions, and only 17% of cases present with history of trauma, as in our patient [5,11].
Plain radiographs of the knee may show phleboliths or amorphous calcifications but generally appear normal [12]. Less than 5% of the cases reported had radiological findings on plain X-rays, namely periosteal reaction, cortical destruction, osteoporosis, advanced maturation of the epiphyses, and arthropathic changes mimicking hemophilia [13]. In our case, soft tissue shadow was observed over the medial aspect of the anterior posterior knee plain radiography, and no other abnormalities were present (Fig. 5).
With regard to soft tissue lesions, MRI is the imaging method of choice and is non-invasive. These lesions generally appear as areas of high signal intensity on both T1 and T2 images compared to most soft tissue tumors, which display intermediate signal intensity on T1 and high signal intensity on T2 [14]. Ultrasonography (US) shows a venous type signal within isoechogenic or hyperechogenic mass [3]. In our case, the US showed an organized hematoma; however, a soft tissue neoplastic lesion could not be ruled out, particularly as the vascularity was significantly increased. MRI showed lobulated irregular enhanced hypervascular mass. MRI imaging differential diagnoses include villonodular synovitis, synovial osteochondromatosis, synovial sarcoma, and the cystic hyperplasia of the synovial or lipoma aborescens [8]. MRI imaging is considered the diagnostic method of choice for the diagnosis and management of synovial lesions in the knee [15].
Management of theses lesion varies from angiographic embolization to surgery or laser therapy. Other options, such as steroids, chemotherapy, and radiotherapy, with a combination of surgery, are not favored due to complications such as scarring, deformity, intraoperative bleeding, or recurrence [1]. In our case, based on the MRI findings, we opted for wide excision due to the pain that the patient was experiencing. According to the literature, the recurrence rate depends on the structure involved [16]. Diffuse involvement of the lesion will have high recurrence rate than local involvement [17]. There is recurrence rate of 17-20% of the diffuse intramuscular cavernous hemangiomas if inadequate resection was done [18]. Recurrence rate is higher in extremities particularly hand, foot, and forearm; the reason of that is the high rate involvement of neurovascular structures and the challenging aspect of fully resecting it [19]. In our case, the lesion was localized and it was completely resected. It was sent for microbial and histopathological examinations; results showed cavernous hemangioma with negative margins of malignancy.

Conclusion
Clinical presentation of cavernous hemangioma varies from painless tumors to mechanical irritation over the knee. Only 17% of cases present with a history of trauma. These rare, benign tumors can cause morbidity if not diagnosed and managed early. Care should be taken whenever there is recurrent swelling and pain over the joint with no signs of infection or trauma, and further investigation, including MRI, should be conducted. Delayed diagnosis may significantly increase the risk of invasion and damage to the joint, leading to increased patient morbidity. Surgical wide excision is the treatment of choice for these lesions.