MRI features of cystic lesions around the knee

Association of complicated Baker's cysts with knee pathologies as compared to simple Baker's cysts

Baker's cysts (BCs) are known to be associated with intra-articular pathologies. BCs can be classified into 2 types: simple and complicated. Although some studies have focused on BC using magnetic resonance imaging (MRI), which is the gold standard examination, no study has compared knee MRI features in patients with simple and complicated BCs. To assess the relationship between the type of BC (simple vs complicated) and other knee pathologies using MRI. Seventy patients who underwent knee MRI examination due to symptomatic knee were retrospectively recruited from April 2011 to April 2021 at a single hospital. In the knee MRI images, the following were assessed: type (simple or complicated), morphology, volume of BCs, thickness of the suprapatellar recess, presence of synovial proliferation of the suprapatellar recess, grade of knee joint effusion, presence of meniscal tear, and extent of meniscal extrusion. The patients were classified into 2 groups according to the type of BC: simple BC and complicated BC. The differences between the 2 groups were evaluated for all variables. Finally, 52 patients were included in this study, 15 were classified as "simple BC" group and 37 as "complicated BC" group. The volume of complicated BC (median: 4.6, interquartile range - IQR: 1.6-12.4) was significantly greater than that of simple BC (median: 0.7, IQR: 0.3-3.7; P = .007). The presence of synovial proliferation in the suprapatellar recess was significantly higher in complicated BC (91.9%) than that in simple BC (46.7%; P = .001). The thickness of the suprapatellar recess was significantly greater in complicated BC (median: 7.5, IQR: 5.8-10.7) than that in simple BC (median: 4.3, IQR: 2.3-7.6; P = .020). The medial meniscus extrusion was greater in complicated BC (median: 4.1, IQR: 2.8-5.1) than that in simple BC (median: 2.5, IQR: 1.8-4.4; P = .037). After adjusting these P-values using the Holm method, only the presence of synovial proliferation in the suprapatellar recess remained significant (P = .010). Using knee MRI images, we demonstrated that complicated BCs are more associated with intra-articular pathologies than simple BCs; such as cyst volume, amount of the knee joint effusion, synovial proliferation and medial meniscal extrusion. Among them, the presence of synovial proliferation was the most significant factor associated with complicated BCs.

Neoplastic and Non-neoplastic Soft Tissue Lesions Around the Knee

Neoplastic and non-neoplastic soft tissue masses around the knee are often incidental findings. Most of these lesions are benign with typical imaging characteristics that allow a confident diagnosis. However, some of these incidental neoplastic masses are characterized by morbidity and potential mortality. This review highlights the typical aspects of these lesions, facilitating a correct diagnosis.

Cystic lesions and bursae around the knee: do they matter in knee osteoarthritis?

The cause of knee osteoarthritis (OA) and knee pain associated with OA is not well understood. Periarticular cystic lesions and bursae around the knee are among the most common morphologic features identified on MRI in the setting of OA. Despite widespread association of these lesions with knee OA and their inclusion in semiquantitative MRI scoring assessment systems for knee OA, the role that these lesions play in the development of knee pain and OA remains uncertain. In this discussion, we review the cystic lesions and bursae most commonly associated with OA of the knee, examine their relation and role in whole organ imaging assessments of OA, and present the literature investigating the associations of periarticular cysts and cyst-like lesions with knee pain and OA.

Automated detection of knee cystic lesions on magnetic resonance imaging using deep learning

Background

Cystic lesions are frequently observed in knee joint diseases and are usually associated with joint pain, degenerative disorders, or acute injury. Magnetic resonance imaging-based, artificial intelligence-assisted cyst detection is an effective method to improve the whole knee joint analysis. However, few studies have investigated this method. This study is the first attempt at auto-detection of knee cysts based on deep learning methods.

Methods

This retrospective study collected data from 282 subjects with knee cysts confirmed at our institution from January to October 2021. A Squeeze-and-Excitation (SE) inception attention-based You only look once version 5 (SE-YOLOv5) model was developed based on a self-attention mechanism for knee cyst-like lesion detection and differentiation from knee effusions, both characterized by high T2-weighted signals in magnetic resonance imaging (MRI) scans. Model performance was evaluated via metrics including accuracy, precision, recall, mean average precision (mAP), F1 score, and frames per second (fps).

Results

The deep learning model could accurately identify knee MRI scans and auto-detect both obvious cyst lesions and small ones with inconspicuous contrasts. The SE-YOLO V5 model constructed in this study yielded superior performance (F1 = 0.879, precision = 0.887, recall = 0.872, all class mAP0.5 = 0.944, effusion mAP = 0.945, cyst mAP = 0.942) and improved detection speed compared to a traditional YOLO model.

Conclusion

This proof-of-concept study examined whether deep learning models could detect knee cysts and distinguish them from knee effusions. The results demonstrated that the classical Yolo V5 and proposed SE-Yolo V5 models could accurately identify cysts.

Baker's Cyst

The authors present a case of a Baker's cyst in the right leg of an 86-year-old woman, whose presentation was more typical for a deep venous thrombosis. Both conditions have inflammation and acute calf pain. The clinical manifestations, imaging findings, and treatment of this common emergency department presentation are discussed.

Fat Chance for Hidden Lesions: Pictorial Review of Hoffa's Fat Pad Lesions

Hoffa's fat pad (HFP) is the most commonly afflicted among all the knee fat pads. Anterior knee pain is common in various pathologies of HFP, as it is richly innervated. A potpourri of the intrinsic and extrinsic pathologies and the tumors and tumor-like conditions affect HFP, and MRI remains the fundamental modality to assess them and provide a specific diagnosis.

Giant intraosseous ganglion of the fibula: multimodality imaging

Intraosseous ganglia around the knee are most commonly located in the proximal tibia and limited to the epiphyseal-metaphyseal region. We report the case of a giant intraosseous ganglion of the fibula. MRI demonstrated the fluid avascular content of the lesion. CT arthrography of the knee demonstrated partial opacification of the lesion through a cortical bone defect. The lesion was treated with curettage and bone grafting. Anatomopathological examination confirmed the medical imaging diagnosis of intraosseous ganglion. This case highlights the value of joint opacification with CT arthrography to demonstrate the communication between the articular cavity and the ganglion.

Multiple Subchondral Bone Cysts Cause Deterioration of Articular Cartilage in Medial OA of Knee: A 3D Simulation Study

Aims

To investigate the impact of subchondral bone cysts (SBCs) in stress-induced osseous and articular variations in cystic and non-cystic knee models using finite element analysis.

Materials and Methods

3D knee joint models were reconstructed from computed tomography (CT) and magnetic resonance imaging (MRI). Duplicate 3D models were also created with a 3D sphere mimicking SBCs in medial tibia. Models were divided into three groups. In group A, a non-cystic knee model was used, whereas in groups B and C, SBCs of 4 and 12 mm size were simulated, respectively. Cyst groups were further divided into three sub-groups. Each of sub-group 1 was composed of a solitary SBC in the anterior half of tibia adjacent to joint line. In sub-group 2, a solitary cyst was modeled at a lower-joint location, and in sub-group 3, two SBCs were used. All models were vertically loaded with weights representing double- and single-leg stances.

Results

During single-leg stance, increase in subchondral bone stress in sub-groups B-1 and B-3 were significant (p = 0.044, p = 0.026). However, in sub-group B-2, a slight increase was observed than non-cystic knee model (9.93 ± 1.94 vs. 9.35 ± 1.85; p = 0.254). All the sub-groups in group C showed significantly increased articular stress (p < 0.001). Conversely, a prominent increase in peri-cystic cancellous bone stress was produced by SBCs in groups B and C (p < 0.001). Mean cartilage shear stress in sub-groups B-1 and B-2 (0.66 ± 0.56, 0.58 ± 0.54) was non-significant (p = 0.374, p = 0.590) as compared to non-cystic model (0.47 ± 0.67). But paired cysts of the same size (B-3) produced a mean stress of 0.98 ± 0.49 in affected cartilage (p = 0.011). Models containing 12 mm SBCs experienced a significant increase in cartilage stress (p = 0.001, p = 0.006, p < 0.001) in sub-groups C-1, C-2, and C-3 (1.25 ± 0.69, 1.01 ± 0.54, and 1.26 ± 0.59), respectively.

Conclusion

The presence of large-sized SBCs produced an increased focal stress effect in articular cartilage. Multiple cysts further deteriorate the condition by increased osseous stress effect and high tendency of peripheral cyst expansion in simulated cystic knee models than non-cystic knee models.

The prevalence and characteristics of osseous erosions associated with parameniscal cysts on knee MRI

OBJECTIVES

To determine the prevalence and characteristics of erosions associated with parameniscal cysts (PMCs) and to evaluate the profile of the associated meniscal tears MATERIALS AND METHODS: PACS database was reviewed for knee MRI scans performed over a 5-year period identifying those with PMCs in patients aged 18 years and above. The scans with PMCs were evaluated for the presence of associated osseous erosions. These erosions and PMCs were then analyzed.

RESULTS

The search revealed 6773 knee MRI examinations, of which 555 had confirmed PMCs. There were 7 PMC-associated erosions for a prevalence of 1.3% (95% CI 0.6, 2.6). All erosions involved the proximal tibia. Three of 7 erosions had underlying marrow edema, and 4 out of 7 had an overhanging margin. The mean dimension of all PMCs was 13 mm (SD = 11). The mean dimension of PMCs associated with erosions was 38 mm (SD = 22), while that of PMCs without erosions was 12 mm (SD = 10) (P < 0.001, Wilcoxon rank sum test). Ninety-three percent (95% CI 90.5, 94.8) of PMCs had associated meniscal tears, most commonly of the horizontal type (57%). All PMCs with underlying erosions were associated with meniscal tears, most commonly complex type tears (5/7).

CONCLUSION

Erosions can rarely be associated with contiguous parameniscal cysts (PMCs). These cysts are significantly larger compared with those without underlying erosions.

Leukocyte-rich platelet-rich plasma application in post-traumatic osteoarthritis with popliteal cyst: a case report

Aim: To describe the successful treatment of a Baker's cyst in the setting of post-traumatic osteoarthritis using ultrasound-guided injection of platelet-rich plasma. Setting: Outpatient sports clinic. Patient: 29-year old male basketball player. Case description: The patient presented with 2-months history of right knee pain, 17 months after undergoing right knee anterior cruciate ligament reconstruction surgery. Exam revealed medial joint line and medial collateral ligament tenderness with posterior knee swelling. After aspiration, a corticosteroid injection was administered with temporary symptom relief. Diagnostic ultrasound examination confirmed the Baker's cyst. The patient then underwent two serial leukocyte-rich platelet-rich plasma injections into his right knee. Results: The patient reported complete resolution of pain and cyst size. Conclusion: Leukocyte-rich platelet-rich plasma may be considered as a treatment option for patients with Baker's cysts in the setting of post-traumatic osteoarthritis.

Epidermal inclusion cyst of the knee

Epidermoid cysts are asymptomatic, slowly enlarging, firm to fluctuant, dome-shaped lesions. Epidermoid cysts frequently appear on the trunk, neck, face, and scrotum, behind the ears and in the palmoplantar region. We review all the cases of epidermoid cyst of the knee and present a case of non-traumatic-induced epidermal cyst in the popliteal fossa of a 66-year-old male with 10-year history of right knee swelling, which appeared firstly as a small mass 2 × 2 cm in the popliteal aspect of the knee. The mass was increasing gradually in size until 2 years ago when it increased suddenly to gain the dimensions of 4 × 6 cm. MRI of the right knee revealed a well-defined cystic lesion in the subcutaneous tissue measuring about 7 × 5 × 5 cm containing internal debris and septations. He underwent complete surgical excision of the mass. The pathological results revealed an epidermal inclusion cyst. To the best of our knowledge, this is the second description for epidermal inclusion cyst involving the popliteal fossa. We were able to retrieve three cases of epidermal cyst of the knee from the literature since its first description in 2004. Including our case, we had a total of four cases of epidermal cyst of the knee. Three males and one female constituted the patients' sample. The mean age for the patients is 55. The epidermal cyst occurred equally in both knees. The popliteal fossa was the location for two epidermal cysts. Similarly, the prepatellar region was the location for another two cysts.

Infected Baker's Cyst: A New Classification, Diagnosis and Treatment Recommendations

Introduction:

Baker’s cyst has a high prevalence in adult population. Despite being usually asymptomatic, cyst complications may develop, such as an infection, rupture and content dissemination into the calf. This clinical presentation has a low incidence with few reports in the literature. We have not found any publication describing a systematic approach for its treatment. The purpose of this study is to propose a new classification, diagnosis, and treatment recommendations based on a case report and a literature review to guide physicians on the best course of treatment.

Case Report:

A 53-year-old man presented with sudden left popliteal pain associated with progressive knee and calf swelling and limited knee flexion. After the initial evaluation, a Baker’s cyst rupture and dissemination into the calf, associated with a septic arthritis, were diagnosed. An arthroscopic surgical irrigation of the knee and open debridement of the calf collection were performed.

Conclusion:

Our classification may allow an accurate and structured description of the different stages of Baker’s cyst presentations, with simplification of the clinical description, diagnosis, and treatment approaches.

Accuracy and efficacy of ultrasound-guided pes anserinus bursa injection

PURPOSE

To compare the accuracy and efficacy of ultrasound (US)-guided versus blind pes anserinus bursa (PAB) injection in patients with pes anserinus tendinobursitis (PATB).

METHODS

Forty-seven patients with clinically diagnosed PATB were randomly assigned to a US-guided group or a blind group of steroid injection. In the US-guided group, the injectate was delivered under sonographic visualization. In the blind group, the conventional technique was used without any visual guidance. After the PAB injection, the injectate location was identified using US in both groups. Treatment effects were assessed using the visual analogue scale (VAS) of knee tenderness. Outcomes were measured before, 1 week and 4 weeks after the injection.

RESULTS

Both groups showed pain relieving at 1 week and 4 weeks after the injection. The injectate in the US guided group were found to be accurately at the PAB in all subjects, whereas blind group were found to be just in 4 of 22 subjects. The US-guided group showed significant improvement of both of VAS scores compared to the blind group at 1 week and 4 weeks after the injection (P < .05).

CONCLUSION

Our results suggest that US-guided PAB injection is more accurate and effective than blind injection in patients with PATB.

Giant infrapatellar ganglion cyst of Hoffa's fat pad

We present the case of a 36-year-old woman who works as a kindergarten teacher, often she is kneeling on her knees due to the nature of the job. Since a year ago, she noticed that her right knee was swelling. She had an orthopaedic examination when she could no longer bend her knee. Inspection and palpation revealed the swelling of the anterior and anterior-lateral aspect of the knee. MRI imaging revealed a large, sharply defined, lobulated lesion of the infrapatellar fat pad. After the surgical incision, a lobular lesion was found and surgically removed. Histological analysis confirmed a ganglion cyst.

Validation of scoring hip osteoarthritis with MRI (SHOMRI) scores using hip arthroscopy as a standard of reference

PURPOSE

To validate SHOMRI gradings in preoperative hip magnetic resonance imaging (MRI) with intra-arthroscopic evaluation of intraarticular hip abnormalities.

METHODS

Preoperative non-arthrographic 3.0-T MRIs of 40 hips in 39 patients (1 patient with bilateral hip surgery) with femoroacetabular impingement (FAI) syndrome (mean age, 34.7 years ± 9.0; n = 16 females), refractory to conservative measures, that underwent hip arthroscopy were retrospectively assessed by two radiologists for chondrolabral abnormalities and compared with intra-arthroscopic findings as the standard of reference. Arthroscopically accessible regions were compared with the corresponding SHOMRI subregions and assessed for the presence and grade of cartilaginous pathologies in the acetabulum and femoral head. The acetabular labrum was assessed for the presence or absence of labral tears. For the statistical analysis sensitivity and specificity as well as intraclass correlation (ICC) for interobserver agreement were calculated.

RESULTS

Regarding chondral abnormalities, 58.8% of the surgical cases showed chondral defects. SHOMRI scoring showed a sensitivity of 95.7% and specificity of 84.8% in detecting cartilage lesions. Moreover, all cases with full-thickness defects (n = 9) were identified correctly, and in n = 6 cases (out of n = 36 with partial-thickness defects) the defective cartilage was identified but the actual depth overestimated. Labral tears were present in all cases and the MR readers identified 92.5% correctly. ICC showed a good interobserver agreement with 86.3% (95% CI 80.0, 90.6%) CONCLUSION: Using arthroscopic correlation, SHOMRI grading of the hip proves to be a reliable and precise method to assess chondrolabral hip joint abnormalities.

KEY POINTS

• Assessment of hip abnormalities using MRI with surgical correlation. • Comparing surgery and MRI by creating a hybrid anatomic map that covers both modalities. • Non-arthrographic use of 3.0-T MRI provides detailed information on cartilage and labral abnormalities in hip joints.

Clinics in diagnostic imaging (185)

A 20-year-old National Serviceman presented with left knee pain and swelling after training for his physical fitness test. Lateral knee radiography and magnetic resonance (MR) imaging showed patellar tendon-lateral femoral condyle friction syndrome (PT-LFCFS), on a background of patella alta and patellar malalignment. The patient was treated non-operatively with a course of physiotherapy and given advice on rest and activity modification. PT-LFCFS is a less well-recognised but important cause of anterior knee pain and represents an entity in a spectrum of disorders related to patellofemoral instability. We herein discuss the MR imaging findings specific to and associated with this condition, as well as briefly describing treatment options. In addition, we showcase a range of commonly encountered abnormalities that affect the infrapatellar fat pad and briefly discuss their specific MR imaging findings.

Magnetic Resonance Imaging of Cysts, Cystlike Lesions, and Their Mimickers Around the Knee Joint

While interpreting routine magnetic resonance imaging (MRI) of the knee joint, a radiologist may encounter various cystic lesions such as ganglion, synovial, and meniscal cysts, among others. In some cases, MRI may demonstrate cystlike lesions around the knee due to fluid distention of normal bursa and recesses, the diagnosis of which should not be difficult if a radiologist is familiar with their characteristic location and MRI appearance. In addition, there are cyst mimickers such as hematomas, abscesses, vascular lesions, and neoplasms around knee joint that may pose a diagnostic challenge on routine MRI. Due to their atypical location and variable morphology, contrast administration is helpful as the enhancement pattern aids to differentiate them from cysts and cystlike lesions. This pictorial essay aims to classify cysts, cystlike lesions, and cyst mimickers in and around the knee joint based on their anatomic location and highlight their characteristic MRI features.

The Sonographic Spectrum of Baker Cysts

Baker cysts are the most common pathologic finding in the sonography of the popliteal fossa. They have a wide range of sonographic appearances. Some of them may need to be recognized and differentiated from other popliteal lesions. Therefore, familiarity with their different imaging appearances is useful for clinical practice. This review summarized different presentations of Baker cysts. They are described in several categories, organized according to their shape and formation: typical Baker cysts and their mild variations, atypical small Baker cysts, ʎ-shaped Baker cysts and their related variations, Baker cysts with extension into nearby muscles, and Baker cysts with complications. The related differentiations are included in each category. The pathogenesis of Baker cysts is also discussed.

Investigating the Effect of Extracorporeal Shock Wave Therapy on Reducing Chronic Pain in Patients with Pes Anserine Bursitis: A Randomized, Clinical- Controlled Trial

Background:

Knee pain, is one of the most common causes of patients’ referring to physiatric clinics, and several factors, are involved in its creation. One of these factors is pes anserine bursitis (PAB) for which various treatment methods are used. This study aims to investigate the effect of this method on reducing chronic pain in these patients.

Materials and Methods:

This clinical trial was conducted in 2013- 2014 on patients with PAB referring to academic, physical medicine clinics. The patients with chronic PAB (pain duration more than 3 months), who were refractory to conservative treatments, were randomly divided into two 20-member experimental groups (extracorporeal shock wave therapy [ESWT] and sham ESWT). Pain scores of all patients were measured using the Visual Analog Scale (VAS) and McGill Pain Questionnaire (MPQ) (total and present pain indexes [TPIs and PPIs]) before intervention, immediately after intervention (3^rd week), and after 8 weeks. The pain scores were then compared and statistically analyzed.

Results:

In the ESWT group, the mean patient pain score of the VAS and TPI in MPQ were significantly lower than in the sham ESWT group immediately after intervention (3^rd week): P =0.02, P = 0.04 respectively; and 8 weeks after the end of treatment: P =0.01, P = 0.000. Moreover, the PPI in both groups had significantly decreased over time, although in ESWT group this decrement was significantly more than sham ESWT group (P < 0.001).

Conclusion:

The results showed that ESWT could be effective in reducing the pain and treating PAB.

The iliotibial tract: imaging, anatomy, injuries, and other pathology

The iliotibial tract, also known as Maissiat's band or the iliotibial band, and its associated muscles function to extend, abduct, and laterally rotate the hip, as well as aid in the stabilization of the knee. A select group of associated injuries and pathologies of the iliotibial tract are seen as sequela of repetitive stress and direct trauma. This article intends to educate the radiologist, orthopedist, and other clinicians about iliotibial tract anatomy and function and the clinical presentation, pathophysiology, and imaging findings of associated pathologies. Specifically, this article will review proximal iliotibial band syndrome, Morel-Lavallée lesions, external snapping hip syndrome, iliotibial band syndrome and bursitis, traumatic tears, iliotibial insertional tendinosis and peritendonitis, avulsion fractures at Gerdy's tubercle, and Segond fractures. The clinical management of these pathologies will also be discussed in brief.

Magnetic resonance imaging of degenerative changes of the posterior cruciate ligament

Background Mucoid degeneration and ganglia reflect a continuum of degenerative changes within the posterior cruciate ligament (PCL). Purpose To assess the prevalence of and radiologists' familiarity with PCL mucoid degeneration and ganglia. Material and Methods Knee magnetic resonance imaging (MRI) from July 2013 to June 2015, excluding patients who had a preceding trauma or MRI findings indicative of a prior injury, were retrospectively reviewed, with the specific request to assess degenerative changes of the PCL, by the same musculoskeletal radiologists who previously reported these examinations, and one fellow. Results A total of 692 patients entered this study. The radiologists and the fellow together identified mucoid degeneration in 34 patients (4.9%), ganglia in 14 patients (2.0%), and both in four patients (0.6%). Several patterns of PCL mucoid degeneration were identified: diffuse thickening in seven patients, partial thickening in 16 (four associated with a ganglion), longitudinal intraligamentous PCL signal-intensity abnormalities resembling a "tram track" in 15. In all cases there was increased signal intensity on fluid-sensitive sequences. In the previous reports, only three cases of PCL mucoid degeneration out of 38 (7.9%) were described, with intraligamentous PCL signal-intensity abnormalities. In the reports of the patients with degeneration and ganglia, only ganglia were described. In the previous reports, ganglia were correctly diagnosed. Conclusion Mucoid degeneration of the PCL is much more common than previously assumed and is underestimated by radiologists.

Lesions involving the outer surface of the bone in children: a pictorial review

Background

Lesions involving the outer cortical surface of the bone occur quite often among children. Broadly, these include benign cortical, juxtacortical and periarticular lesions, dysplasias affecting the cortical bone, regional and diffuse periosteal pathology and malignant tumours. Some of these lesions are unique to the paediatric population; others are more frequently seen among children than adults — yet others have an adult predilection but can occasionally be seen in children.

Methods

A complete list of differential considerations for lesions involving the outer cortical surface of the bone in children is presented. Imaging characteristics on plain film radiography and MR are described in association with multiple examples and illustrations.

Conclusion

A pictorial review detailing the imaging features of surface lesions of the bone in children will be a useful aide for both radiologists and their clinical colleagues, and will help them sort their way through the maze of differential diagnoses for these abnormalities.

Teaching Points

• Surface lesions of bones in children comprise a distinct entity and differ from those in adults.

• Imaging plays an important role towards classifying surface lesions of bones in children.

• MRI features may be characteristic and aid precise diagnosis, thus guiding further management.

Effects of kinesiotaping versus non-steroidal anti-inflammatory drugs and physical therapy for treatment of pes anserinus tendino-bursitis: A randomized comparative clinical trial

OBJECTIVE

Pes anserinus tendino-bursitis is a condition caused by repetitive friction over the bursa or direct trauma to knee joint and it presents with proximal medial tibial pain and swelling. The aim of this study is to determine the effects of kinesiotaping in comparison with naproxen and physical therapy in treatment of pes anserinus tendino-bursitis.

METHODS

In a randomized comparative clinical trial 56 patients with clinical diagnosis of pes anserinus tendino-bursitis were randomly assigned to kinesiotaping and naproxen/physical therapy (28 patients in each group). Kinesiotaping on the tender area in the form of space-correction (lifting) technique was used and repeated for three times with a one-week interval. Another group received naproxen (250mg TID for 10 days) and ten sessions of daily physical therapy. The visual analog scale (VAS) was used for evaluation of pain. The depth of swelling of the area was measured with sonography before and after treatment. Wilcoxon signed ranks test has been used for determining the influence of interventions on pain (VAS) and swelling scores in each group. The ANCOVA (Analysis of covariance) test was applied for comparing the influence of interventions on VAS and swelling scores after adjustment for co-variables.

RESULTS

At end of the study, 27 patients remained in the kinesiotaping group and 19 patients in naproxen/physical therapy group. Treatment with kinesiotaping significantly decreased the pain (P=0.0001) and swelling scores (P=0.0001) in comparison with naproxen/physical therapy after adjustment for baseline characteristics. Kinesiotaping was safe without any complications except for a mild local skin irritation in one patient.

CONCLUSION

Kinesiotaping is more effective than naproxen plus physical therapy in reduction of pain and swelling in patients with pes anserinus tendino-bursitis.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov identifier is NCT01680263.

Hypertonic Dextrose Injection for The Treatment of a Baker's Cyst

We present extremely rare and interesting case of a Baker's cyst treated with hypertonic dextrose injection. A 54-year-old female patient had a Baker's cyst which was diagnosed by an ultrasonography. After the failure of the two-weekly conservative treatment, we injected hypertonic dextrose (25%) into her right knee joint for the treatment of a Baker's cyst. Two weeks after the injection, the patient reported improvement in posterior knee pain, and an US showed a resolution of the posterior knee cyst. Certainly hypertonic dextrose injection for the treatment of a Baker's cyst appears to be a reasonable treatment option. Further studies are needed in order to elucidate the efficacy of hypertonic dextrose injection in the treatment of Baker's cysts.

Hoffa's fat pad abnormalities, knee pain and magnetic resonance imaging in daily practice

Hoffa's (infrapatellar) fat pad (HFP) is one of the knee fat pads interposed between the joint capsule and the synovium. Located posterior to patellar tendon and anterior to the capsule, the HFP is richly innervated and, therefore, one of the sources of anterior knee pain. Repetitive local microtraumas, impingement, and surgery causing local bleeding and inflammation are the most frequent causes of HFP pain and can lead to a variety of arthrofibrotic lesions. In addition, the HFP may be secondarily involved to menisci and ligaments disorders, injuries of the patellar tendon and synovial disorders. Patients with oedema or abnormalities of the HFP on magnetic resonance imaging (MRI) are often symptomatic; however, these changes can also be seen in asymptomatic patients. Radiologists should be cautious in emphasising abnormalities of HFP since they do not always cause pain and/or difficulty in walking and, therefore, do not require therapy. Teaching Points • Hoffa's fat pad (HFP) is richly innervated and, therefore, a source of anterior knee pain. • HFP disorders are related to traumas, involvement from adjacent disorders and masses. • Patients with abnormalities of the HFP on MRI are often but not always symptomatic. • Radiologists should be cautious in emphasising abnormalities of HFP.

Joint effusion of the knee: potentialities and limitations of ultrasonography

PURPOSE

This study aimed at comparing the diagnostic accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) for the detection of joint effusion of the knee.

METHODS

For this retrospective study, approbation by the institutional review board was not required, and written informed consent from the patients was waived. One hundred and fifty-eight patients (83 men and 75 women; median age 41.2 years; age range 13-81 years) who underwent US and MRI of the knee were included in the study. The sensitivity and specificity of US with respect to MRI in the evaluation of the effusion of the knee and in each recess were compared.

RESULTS

In evaluating joint effusion of the knee, compared with MRI, US correctly identified 78 of 96 patients with joint effusion, showing a sensitivity of 81.3 % and a specificity of 100 %, with a positive predictive value (PPV) of 100 % and a negative predictive value (NPV) of 77.5 % (p value = 0.001). Various results were obtained comparing ultrasound with MRI, regarding the various recesses.

CONCLUSION

US showed high specificity and sensitivity in diagnosing knee joint effusion and could be used in patients who cannot undergo MRI.

Pyogenic Baker cyst in a patient with psoriatic arthritis during etanercept therapy

Patients with psoriatic arthritis (PsA) are at increased risk of infection due to disease course or treatment-related immunodeficiency. We describe a patient with a 10-year history of PsA, with arthritis of the right knee and pain and edema in the right calf, treated with the TNFa inhibitor etanercept for 6 months. Ultrasound showed accumulation of hypoechoic fluid, which was aspirated and was positive for staphylococcus and aspergillus. The patient recovered after surgical drainage and four weeks of antibiotic and antifungal therapy.

Knee bursitis: a sonographic evaluation

OBJECTIVE

To evaluate the use of ultrasound for the diagnosis of knee bursitis.

MATERIALS AND METHODS

One-hundred and fifty-eight patients who, from May 2013 to May 2014, had an ultrasound examination of the knee and magnetic resonance imaging (MRI) of the knee during the following month were eligible for the study. The exams were reviewed by two musculoskeletal radiologists with 20 years of experience.

RESULTS

Of these patients, 15 (7 men, 8 women) had bursitis, while 143 (76 men, 67 women) had no bursitis. In evaluating knee bursitis, US, when compared to MRI, correctly identified 13 out of 15 cases of bursitis, showing a sensitivity of 86.67 %, specificity 100 %, and K index of 0.92. Particularly in the suprapatellar bursa, ultrasound showed bursitis in 5 cases versus 7 by MRI (sensitivity of 71.4 %, specificity of 100 %, and K index of 0.82).

CONCLUSION

Ultrasound can be used as a valuable tool for the evaluation of bursitis of the superficial bursae in patients who cannot undergo MRI.

Popliteal cysts: a current review

Baker's cyst, or popliteal cyst, is a fluid-filled mass that is a distention of a preexisting bursa in the popliteal fossa, most commonly the gastrocnemio-semimembranosus bursa. This bursa is unique in that it communicates with the knee joint, unlike other periarticular bursae, via an opening in the joint capsule posterior to the medial femoral condyle. Many have theorized that this opening creates a valve-like mechanism in the presence of effusion that contributes to the formation of these cysts in adults. Popliteal cysts rarely manifest alone and are most often found in conjunction with other intra-articular pathologies and inflammatory conditions, such as osteoarthritis, meniscus tears, and rheumatoid arthritis. In children, popliteal cysts are only occasionally associated with these conditions and are more often an incidental finding discovered during a routine physical examination. Popliteal cysts may present as either a chronically persistent or relapsing condition or as an acute and dramatic condition that can occur in the case of cyst rupture presenting as pseudothrombophlebitis. Ultrasound and magnetic resonance imaging have proven to be consistent and accurate in the confirmation of popliteal cysts, with magnetic resonance imaging becoming the modern imaging modality of choice. This review discusses the anatomy and etiology of popliteal cysts, describes the common clinical presentations, reviews the differential diagnoses, and provides guidance for proper diagnostic imaging. It also provides a comparison of current conservative, minimally invasive, and invasive treatment options, along with a discussion of results. Postoperative rehabilitation depends largely on the condition associated with the popliteal cyst.

Cysts and cystic-appearing lesions of the knee: A pictorial essay

Cysts and cystic-appearing lesions around the knee are common and can be divided into true cysts (synovial cysts, bursae, ganglia, and meniscal cysts) and lesions that mimic cysts (hematomas, seromas, abscesses, vascular lesions, and neoplasms). The specific anatomic location of the cystic lesion often permits the correct diagnosis. In difficult cases, identifying a cystic mass in an atypical location and/or visualizing internal solid contrast enhancement on magnetic resonance imaging (MRI) should raise concern for a neoplasm and the need for further evaluation and intervention.

Popliteal cysts and subgastrocnemius bursitis are associated with knee symptoms and structural abnormalities in older adults: a cross-sectional study

Introduction

The role of popliteal cysts and subgastrocnemius bursitis in knee joint homeostasis is uncertain. The aim of this study is to describe cross-sectional associations between popliteal cysts, subgastrocnemius bursitis, knee symptoms and structural abnormalities in older adults.

Methods

A cross-sectional sample of 900 randomly-selected subjects (mean age 63 years, 48% female) were studied. Knee pain, stiffness and dysfunction were assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire. Radiographic knee osteophyte and joint space narrowing (JSN) were recorded. Magnetic resonance imaging (MRI) was utilized to assess popliteal cysts, subgastrocnemius bursitis, cartilage defects and bone marrow lesions (BMLs).

Results

Popliteal cysts were present in 11.7% and subgastrocnemius bursitis in 12.7% of subjects. Subgastrocnemius bursitis was more common in those with popliteal cyst (36.2% versus 9.7%, P <0.01). In multivariable analyses, popliteal cysts were significantly associated with increased osteophytes in both medial and lateral tibiofemoral compartments while subgastrocnemius bursitis was associated with increased osteophytes and JSN in the medial tibiofemoral compartment. Both were significantly associated with cartilage defects in all compartments, and with BMLs in the medial tibiofemoral compartment. Furthermore, both popliteal cysts and subgastrocnemius bursitis were significantly associated with increased weight-bearing knee pain but these associations became non-significant after adjustment for cartilage defects and BMLs.

Conclusions

Popliteal cysts and subgastrocnemius bursitis are associated with increased symptoms as well as radiographic and MRI-detected joint structural abnormalities. Longitudinal data will help resolve if they are a consequence or a cause of knee joint abnormalities.

Elastographic and contrast-enhanced ultrasound features of a benign schwannoma of the common fibular nerve

Differential diagnosis of a mass in the popliteal fossa includes a number of pathologies, such as Baker's cyst, extra-articular ganglia cyst, hematoma, proliferation of adipose tissue, aneurysm of the popliteal artery, thrombosed varicose vein, gouty tophi and benign or malignant soft tissue tumors. Schwannoma is the most common benign peripheral nerve tumor. However, only a few authors have so far reported on schwannomas located on the common fibular nerve. The aim of this paper is to present contrast-enhanced ultrasound and ultrasound elastographic features of a rare case of schwannoma of the common fibular nerve as well as imaging features of a schwannoma of the peripheral nerve.

MRI characteristics of cysts and "cyst-like" lesions in and around the knee: what the radiologist needs to know

Objectives and Methods

A variety of benign cystic or “cyst-like” lesions may be encountered during a routine magnetic resonance imaging (MRI) of the knee. These lesions comprise a diverse group of entities from benign cysts to complications of underlying diseases. In addition, normal anatomic bursae and recesses may be misdiagnosed as an intra-articular cystic lesion when they are distended. However, the majority of the aforementioned lesions have characteristic MR appearances that allow a confident diagnosis, thus obviating the need for additional imaging or interventional procedures.

Results

This article includes a comprehensive pictorial essay of the characteristic MRI features of common and uncommon benign cysts and “cyst-like” lesions in and around the knee joint.

Discussion

For accurate assessment of the “cystic structure”, a radiologist should be able to identify typical MRI patterns that contribute in establishing the correct diagnosis and thus guiding specific therapy and avoiding unwarranted interventional procedures such as biopsy or arthroscopy.

Teaching points

• Cystic lesions are common in knee MRI and the commonest, the Baker’s cyst, has an incidence of 38 %.

• Synovial cysts, meniscal cysts, normal knee bursae and recesses have characteristic MR appearances.

• Miscellaneous “cyst-like” lesions may require a more dedicated MR protocol for a correct diagnosis.

MR imaging of anterior knee pain: a pictorial essay

Anterior knee pathology is a frequent cause of joint pain and limitation of function and mobility among patients presenting to an orthopaedic department. Proper recognition and treatment of pathologic conditions depend on the knowledge of normal anatomy and of the various abnormalities, which affect this area of the knee and may present with anterior knee pain. A broad array of benign and malignant processes may be manifested as anterior knee discomfort, and this common clinical entity is among the most frequent indications for MR imaging of the lower extremities. Clinical history and physical examination are also of paramount importance. The disorders can be categorized and differentiated primarily according to their location. Traumatic or non-traumatic disorders of the patella, patellar retinacula, quadriceps and patellar tendons and supra or infrapatellar fat pad can be the source of symptoms. This article includes a comprehensive pictorial essay of the characteristic MR features of common and uncommon disorders causing anterior knee pain. For accurate assessment of the aforementioned clinical problem, a radiologist should be able to identify typical MR imaging patterns that contribute in establishing the correct diagnosis and thus tailoring the appropriate therapy. Level of evidence IV.

MR Imaging of Intra- and Periarticular Cyst-Like Lesions of the Knee Joint in Workers with Occupational Kneeling

Objective. To determine the risk of intra- and periarticular cyst-like lesions of the knee joint in occupational kneeling. Methods. Magnetic resonance imaging of both knees (n = 282) was conducted in 92 male floor layers and 49 male graphic designers (referents), with a mean age of 55.6 years (range 42–70 years). The prevalence of cyst-like lesions was computed among floor layers and graphic designers, respectively, and associations with occupation summarized by odds ratio (OR) with 95% confidence intervals (CIs). Using logistic regression, models were adjusted for age, body mass index, knee injuries, and knee-straining sports. Results. Floor layers had a significantly higher prevalence of cyst-like lesions in the posterior part of the knee joint compared to graphic designers (OR 2.70, 95% CI 1.50–4.84). Floor layers also had a higher prevalence of fluid collections in the popliteus tendon recess (OR 2.17, 95% CI 0.99–4.77) and large cystic lesions of the popliteus muscle (OR 3.83, 95% CI 0.78–18.89). The prevalence of cystic lesions in the anterior part of the knee joint was low among floor layers (8.7%) and there was no significant difference between the two trade groups (P = 0.34). Conclusions. Occupational kneeling increases the risk of cyst-like lesions in the posterior part of the knee joint.

An in vivo investigation of the initiation and progression of subchondral cysts in a rodent model of secondary osteoarthritis

Introduction

Subchondral bone cysts (SBC) have been identified in patients with knee osteoarthritis (OA) as a cause of greater pain, loss of cartilage and increased chance of joint replacement surgery. Few studies monitor SBC longitudinally, and clinical research using three-dimensional imaging techniques, such as magnetic resonance imaging (MRI), is limited to retrospective analyses as SBC are identified within an OA patient cohort. The purpose of this study was to use dual-modality, preclinical imaging to monitor the initiation and progression of SBC occurring within an established rodent model of knee OA.

Methods

Eight rodents underwent anterior cruciate ligament transection and partial medial meniscectomy (ACLX) of the right knee. In vivo 9.4 T MRI and micro-computed tomography (micro-CT) scans were performed consecutively prior to ACLX and 4, 8, and 12 weeks post-ACLX. Resultant images were co-registered using anatomical landmarks, which allowed for precise tracking of SBC size and composition throughout the study. The diameter of the SBC was measured, and the volumetric bone mineral density (vBMD) was calculated within the bone adjacent to SBC. At 12 weeks, the ACLX and contralateral knees were processed for histological analysis, immunohistochemistry, and Osteoarthritis Research Society International (OARSI) pathological scoring.

Results

At 4 weeks post-ACLX, 75% of the rodent knees had at least 1 cyst that formed in the medial tibial plateau; by 12 weeks all ACLX knees contained SBC. Imaging data revealed that the SBC originate in the presence of a subchondral bone plate breach, with evolving composition over time. The diameter of the SBC increased significantly over time (P = 0.0033) and the vBMD significantly decreased at 8 weeks post-ACLX (P = 0.033). Histological analysis demonstrated positive staining for bone resorption and formation surrounding the SBC, which were consistently located beneath the joint surface with the greatest cartilage damage. Trabecular bone adjacent the SBC lacked viable osteocytes and, combined with bone marrow changes, indicated osteonecrosis.

Conclusions

This study provides insight into the mechanisms leading to SBC formation in knee OA. The expansion of these lesions is due to stress-induced bone resorption from the incurred mechanical instability. Therefore, we suggest these lesions can be more accurately described as a form of OA-induced osteonecrosis, rather than 'subchondral cysts'.

New insights about suprapatellar cyst

Suprapatellar bursa is located between the quadriceps tendon and femur, and it develops before the birth as a separate synovial compartment proximal to the knee joint. By the fifth month of fetal life there is a suprapatellar septum between the knee joint cavity and suprapatellar bursa which later perforates and involutes in a way that a normal communication between the cavity of bursa and knee is established. A small portion of the embrionic septum can later lag as more or less expressed suprapatellar plica. In case when suprapatellar plica has a small communication with valve mechanism or in case of complete septum, bursa becomes a separate compartment and potential location for the suprapatellar cyst development. Magnetic resonance imaging is recognised as the gold standard in diagnosis of knee cysts because of its ability to show cystic nature of the lesion, its relationship with other anatomic structures, as well as to establish whether other knee pathologies are present. Considering treatment possibilities, majority of cysts around the knee resolve spontaneously and should be treated by aspiration and application of corticosteroids. Suprapatellar cyst is a very rare knee pathology and it can in some occasions be treated using open or arthroscopic surgery.

Semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts of the knee at 3T MRI: a comparison between intermediate-weighted fat-suppressed spin echo and Dual Echo Steady State sequences

BACKGROUND

Choice of appropriate MR pulse sequence is important for any research studies using imaging-derived data. The aim of this study was to compare semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts using intermediate-weighted (IW) fat-suppressed (fs) spin echo and Dual Echo Steady State (DESS) sequences on 3 T MRI.

METHODS

Included were 201 subjects aged 35-65 with frequent knee pain. 3T MRI was performed with the same sequence protocol as in the Osteoarthritis Initiative (OAI). In a primary reading subchondral bone marrow edema-like lesions were assessed according to the WORMS system. Two hundred subregions with such lesions were randomly chosen. The extent of subchondral bone marrow edema-like lesions was re-evaluated separately using sagittal IW fs and DESS sequences according to WORMS. Lesion size and confidence of the differentiation between subchondral bone marrow edema-like lesions and subchondral cysts located within or adjacent to them was rated from 0 to 3. Wilcoxon signed-rank tests and chi-square statistics were used to examine differences between the two sequences.

RESULTS

Of 200 subchondral bone marrow edema-like lesions detected by IW fs sequence, 93 lesions (46.5%) were not depicted by the DESS sequence. The IW fs sequence depicted subchondral bone marrow edema-like lesions to a larger extent than DESS (p < 0.0001), and the opposite was true for subchondral cysts. Confidence scores for differentiation of the two types of lesions were not significantly different between the two sequences.

CONCLUSIONS

In direct comparison the IW fs sequence depicts more subchondral bone marrow edema-like lesions and better demonstrate the extent of their maximum size. The DESS sequence helps in the differentiation of subchondral bone marrow edema-like lesions and subchondral cysts. The IW fs sequence should be used for determination of lesion extent whenever the size of subchondral bone marrow edema-like lesions is the focus of attention.

Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score)

OBJECTIVE

In an effort to evolve semi-quantitative scoring methods based upon limitations identified in existing tools, integrating expert readers' experience with all available scoring tools and the published data comparing the different scoring systems, we iteratively developed the magnetic resonance imaging (MRI) Osteoarthritis Knee Score (MOAKS). The purpose of this report is to describe the instrument and its reliability.

METHODS

The MOAKS instrument refines the scoring of bone marrow lesions (BMLs) (providing regional delineation and scoring across regions), cartilage (sub-regional assessment), and refines the elements of meniscal morphology (adding meniscal hypertrophy, partial maceration and progressive partial maceration) scoring. After a training and calibration session two expert readers read MRIs of 20 knees separately. In addition, one reader re-read the same 20 MRIs 4 weeks later presented in random order to assess intra-rater reliability. The analyses presented here are for both intra- and inter-rater reliability (calculated using the linear weighted kappa and overall percent agreement).

RESULTS

With the exception of inter-rater reliability for tibial cartilage area (kappa=0.36) and tibial osteophytes (kappa=0.49); and intra-rater reliability for tibial BML number of lesions (kappa=0.54), Hoffa-synovitis (kappa=0.42) all measures of reliability using kappa statistics were very good (0.61-0.8) or reached near-perfect agreement (0.81-1.0). Only intra-rater reliability for Hoffa-synovitis, and inter-rater reliability for tibial and patellar osteophytes showed overall percent agreement <75%.

CONCLUSION

MOAKS scoring shows very good to excellent reliability for the large majority of features assessed. Further iterative development and research will include assessment of its validation and responsiveness.