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CASE REPORT
Ahead of print publication  

Suprapatellar bursitis presenting as unilateral “Hot” patella sign on 99mTc-methylene diphosphonate skeletal scintigraphy


 Department of Nuclear Medicine, Yashoda Hospital, Secunderabad, Telangana, India

Date of Submission12-Nov-2020
Date of Decision11-Dec-2020
Date of Acceptance19-Nov-2020
Date of Web Publication22-Sep-2021

Correspondence Address:
Vankadari Kousik,
Head of Department, Department of Nuclear Medicine, Yashoda Hospital, Senunderabad - 500 003, Telangana
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/wjnm.wjnm_148_20

   Abstract 

“Hot” patella sign is a less commonly seen finding in bone scintigraphy defined as increased tracer activity in the patella greater than the ipsilateral distal femur and ipsilateral proximal tibia. We present a case of suprapatellar knee bursitis manifesting as unilateral “hot” patella sign on three-phase 99mTc-methylene diphosphonate bone scintigraphy. This case portrays the image findings of suprapatellar bursitis on three-phase bone scintigraphy.

Keywords: Skeletal scintigraphy, suprapatellar bursitis, unilateral “hot” patella sign



How to cite this URL:
Kousik V, Ram S. Suprapatellar bursitis presenting as unilateral “Hot” patella sign on 99mTc-methylene diphosphonate skeletal scintigraphy. World J Nucl Med [Epub ahead of print] [cited 2021 Oct 21]. Available from: http://www.wjnm.org/preprintarticle.asp?id=326403


   Introduction Top


Bursae are fluid filled sacs lined by synovial membrane that reduce friction and cushion pressure points between muscles and skin, bones and tendons. They are usually present adjacent to joints. Suprapatellar bursa refers to synovial space located posterosuperior to patella in-between tendon of rectus femoris muscle and femur. It usually communicates with knee joint in most of the individuals.[1] Inflammation involving this bursa refers to suprapatellar bursitis.


   Case Report Top


A 52-year-old female presented to our department with dull aching pain in the left anterior knee for 4 days. On clinical examination, the pain was not associated with any external signs of inflammation along with an unrestricted range of motion in the left knee joint. Three-phase 99mTc-methylene diphosphonate (MDP) bone scintigraphy done for further evaluation revealed increased tracer activity in the suprapatellar region of the left knee (black arrows) in early anterior flow [Figure 1]a, anterior blood pool images [Figure 1]b along with minimal increased tracer uptake in the corresponding left anterior knee region in the delayed whole-body image [Figure 1]c and planar static image [Figure 1]d, black arrow]. Axial, sagittal, coronal computed tomography (CT) [Figure 1]e, [Figure 1]f, [Figure 1]g and fused single-photon emission CT/CT images [Figure 1]h, [Figure 1]i, [Figure 1]j localize the increased tracer uptake in the left knee to patella along with fluid collection in the suprapatellar bursa (white arrows). No morphological abnormality is noted in the patella in the corresponding CT images. Based on scan findings of increased flow, blood pool activity in the suprapatellar region, a diagnosis of suprapatellar bursitis was considered. Increased osteoblastic activity involving patella predominantly along the superior rim in the delayed phase imaging is possibly due to reactive increased blood flow to the patella.
Figure 1: (A) Three phase skeletal scintigraphy shows increased flow, (B) blood pool (D) involving the left suprapatellar region along with increased tracer uptake in the left knee in delayed images. (E-J) SPECT-CT images localize increased tracer uptake to left patella along with fluid collection in the left suprapatellar bursa.

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   Discussion Top


Various other causes of “hot” patella sign include fracture, chondromalacia patellae, malignancy, Paget's disease, osteomyelitis, and patellofemoral arthritis following total knee replacement.[2],[3],[4] Chondromalacia patellae often presents as bilateral “hot” patella sign compared to other causes.[3] Patella bone can be site of primary bone tumor apart from metastatic spread from various cancers such as the breast, lung, kidney, esophagus, and cervix along with its involvement in multiple myeloma.[5],[6] Absence of lytic-sclerotic component, erosions, osteophytes, and sclerosis on CT images along with fluid collection in the suprapatellar space in our case excludes mitotic disease, osteomyelitis, osteoarthritis, and Paget's disease favoring a diagnosis of suprapatellar bursitis. In addition, the absence of tenderness over the patella clinically excludes patellar osteomyelitis in our case. Even though monostotic Paget's disease can present as a unilateral “hot” patella sign, it presents with diffuse intense tracer uptake in the patella in the late phase of bone scan compared to our case.[7] Patellar metastases usually present as tracer avid lytic-sclerotic lesion involving part of the patella on 99mTc-MDP bone scan along with increased osteoblastic activity in rest of the lesions in the skeleton.[8] Ahmad et al. reported the association of “hot” patella sign with patellofemoral arthritis and anterior knee pain in the setting of total knee replacement.[9] Patients having “hot” patella sign in that study showed clinical improvement following secondary patellar resurfacing.


   Conclusion Top


This index case emphasizes the importance of three-phase bone scan in musculoskeletal inflammation and lists out various other causes of “hot” patella sign along with its clinical significance on skeletal scintigraphy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Zidorn T. Classification of the suprapatellar septum considering ontogenetic development. Arthroscopy 1992;8:459-64.  Back to cited text no. 1
    
2.
Kankate RK, Selvan TP. Primary haematogenous osteomyelitis of the patella: A rare cause for anterior knee pain in an adult. Postgrad Med J 2000;76:707-9.  Back to cited text no. 2
    
3.
Kipper MS, Alazraki NP, Feiglin DH. The “hot” patella. Clin Nucl Med 1982;7:28-32.  Back to cited text no. 3
    
4.
Kohn HS, Guten GN, Collier BD, Veluvolu P, Whalen JP. Chondromalacia of the patella. Bone imaging correlated with arthroscopic findings. Clin Nucl Med 1988;13:96-8.  Back to cited text no. 4
    
5.
Li G, Shan C, Sun R, Liu S, Chen S, Song M, et al. Patellar metastasis from primary tumor. Oncol Lett 2018;15:1389-96.  Back to cited text no. 5
    
6.
Sun EC, Nelson SD, Seeger LL, Lane JM, Eckardt JJ. Patellar metastasis from a squamous carcinoma of the lung: A case report. Clin Orthop Relat Res 2001:391:234-8.  Back to cited text no. 6
    
7.
Abamor E, Kitapçi MT, Cila E, Gökçora N, Uluoğlu O. Increased accumulation of Tl-201 in monostotic Paget's disease of the patella: Evaluation with quantitative analysis. Clin Nucl Med 2001;26:615-8.  Back to cited text no. 7
    
8.
Stoler B, Staple TW. Metastases to the patella. Radiology 1969;93:853-6.  Back to cited text no. 8
    
9.
Ahmad R, Kumar GS, Katam K, Dunlop D, Pozo JL. Significance of a “hot patella” in total knee replacement without primary patellar resurfacing. Knee 2009;16:337-40.  Back to cited text no. 9
    


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