Prefemoral Fat Pad Research Articles

Association among peripatellar fat pad edema and related patellofemoral maltracking parameters: a case-control magnetic resonance imaging study

BackgroundThe peripatellar fat pads are critical for protective cushioning during movement, and their endocrine function has been shown to affect osteoarthritis. Magnetic resonance imaging (MRI) is frequently used to visualize edema of the peripatellar fat pads due to injury. In this study, we aimed to assess the relationship between peripatellar fat pad edema and patellofemoral maltracking MRI parameters and investigate the association among cases of peripatellar fat pad edema.MethodsAge- and sex-matched peripatellar fat pad edema cases were identified and divided into superolateral Hoffa, quadriceps, and prefemoral groups. Images were assessed according to tibial tuberosity lateralization, trochlear dysplasia, patellar alta, patellar tilt, and bisect offset. McNemar’s test or paired t-tests and Spearman’s correlation were used for statistical analysis. Interobserver agreement was assessed with the intraclass correlation coefficient.ResultsOf 1210 MRI scans, 50, 68, and 42 cases were in the superolateral Hoffa, quadriceps, and prefemoral groups, respectively. Subjects with superolateral Hoffa fat pad edema had a lower lateral trochlear inclination (p = 0.028), higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.021) ratios, and lower patellotrochlear index (p < 0.001) than controls. The prefemoral group had a lower lateral trochlear inclination (p = 0.014) and higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.004) ratios compared with the control group. In contrast, the patellotrochlear index (p = 0.001) was lower. Mean patellar tilt angle (p = 0.019) and mean bisect offset (p = 0.005) were significantly different between cases and controls. The quadriceps group showed no association. Superolateral Hoffa was positively correlated with prefemoral (p < 0.001, r = 0.408) and negatively correlated with quadriceps (p < 0.001, r = -0.500) fat pad edema.ConclusionsSuperolateral Hoffa and prefemoral fat pad edemas were associated with patellar maltracking parameters. Quadriceps fat pad edema and maltracking parameters were not associated. Superolateral Hoffa fat pad edema was positively correlated with prefemoral and negatively correlated with quadriceps fat pad edema.

Friction Syndromes of the Knee

The knee is a complex joint with many fascial and ligamentous interactions. The movement in multiple planes makes the knee a prime site for friction syndromes, especially in active individuals. The most common friction syndrome is the iliotibial band friction syndrome. This occurs commonly in runners and cyclists and can be diagnosed clinically in a patient with lateral knee pain during activity. The anterior fat pads of the knee can also be the site of friction syndromes, most often in the Hoffa fat pad. Edema here can be located in the superolateral aspect of the fat pad when associated with patellar abnormalities, or diffusely when impingement is due to other causes. Edema of the quadriceps or prefemoral fat pad may also cause anterior knee pain and may be diagnosed with magnetic resonance imaging. The posteromedial friction syndrome and medial tibial crest syndrome are rare causes of medial knee pain highly active individuals.

Hyperechoic and Low Morphological Changes in the Prefemoral Fat Pad in Individuals with Knee Osteoarthritis Based on Ultrasonographic Findings.

Background:To clarify the changes in the echo intensity (EI) in the prefemoral fat pad (PFP) and identify the relationship between the PFP and clinical features of knee osteoarthritis (OA).Methods:Twenty-six women with knee OA (mean age: 76 years) and 17 healthy women (mean age: 73 years) were enrolled. The Kellgren and Lawrence grading scale was used for the radiographic evaluation of knee OA. The EI of the PFP was measured as grayscale values. The change ratio of the anteroposterior PFP length during quadriceps contraction was measured. Knee range of motion and pain (100-mm visual analog scale) were evaluated.Results:The EI was significantly higher in the OA group than in the healthy group (P < 0.001). The change ratio of the PFP in the OA group was significantly lower than that in the healthy group (P < 0.001). The ranges of knee flexion and extension were correlated with the EI of the PFP (both P < 0.01) and the change ratio of the PFP (both P < 0.01). There was no significant correlation observed with knee pain.Conclusion:Hyperechoic changes and a decreased change ratio of the PFP were observed in the patients with knee OA. High EI and decreased morphological PFP changes were associated with decreased ranges of motion.

Qualitative and quantitative measures of prefemoral fat pad and quadriceps fat pad predict incident radiographic osteoarthritis

Purpose: To determine if qualitative and quantitative measures of prefemoral fat pad (PFP) and quadriceps fat pad (QFP) are predictive of incident radiographic osteoarthritis (iROA) over 4 years in the Osteoarthritis Initiative (OAI) study.

Hyperintensity alteration in prefemoral fat pad predicts patellofemoral structural degradation in older adults: data from the osteoarthritis initiative

Hyperintensity alteration in prefemoral fat pad predicts patellofemoral structural degradation in older adults: data from the osteoarthritis initiative

Qualitative and quantitative measures of prefemoral and quadriceps fat pads are associated with incident radiographic osteoarthritis: data from the Osteoarthritis Initiative

To determine if qualitative and quantitative measures of prefemoral fat pad (PFP) and quadriceps fat pad (QFP) are associated with incident radiographic osteoarthritis (iROA) over 4 years in the Osteoarthritis Initiative (OAI) study. Participants in this nested case-control study were selected from the OAI study with knees that had Kellgren Lawrence grades (KLG)of 0 or 1at baseline. Case knees were defined by iROA (KLG≥ 2) over 4 years. Control knees without iROA were matched 1:1 with case knees. Magnetic resonance images (MRIs) were read at P0 (time of onset of iROA), P-1 (1 year prior to P0) and baseline, and used to assess PFP (i.e., prefemoral hyperintensity alteration, patellofemoral hyperintensity alteration, maximum axial area) and QFP (i.e., hyperintensity alteration, mass effect, maximum axial area). Conditional logistic regression analyses were performed to study the associations between PFP/QFP measures and iROA, after adjustment for covariates. 354 case knees with iROA were matched to 354 control knees. 66.9% of the participants were female, with an average age of 60.1 years. PFP prefemoral hyperintensity alteration measured at three time points (OR [95%CI]: 1.46 [1.18-1.82], 1.50 [1.20-1.88], 1.52 [1.22-1.89] respectively), PFP maximum axial area (OR [95%CI]: 1.07 [1.01-1.14], 1.08 [1.01-1.15], 1.08 [1.02-1.15] respectively) and QFP hyperintensity alteration (OR [95%CI]: 1.59 [1.27-2.00], 1.44 [1.13-1.82], 1.38 [1.09-1.73] respectively) were significantly associated with iROA in multivariable conditional logistic analyses. QFP mass effect measured at BL and P-1 (OR [95%CI]: 1.42 [1.11-1.82], 1.33 [1.01-1.73] respectively) were significantly associated with iROA. Qualitative and quantitative measures of PFP and QFP are associated with increased iROA over 4 years.

Are Patellofemoral Joint Alignment and Shape Associated With Structural Magnetic Resonance Imaging Abnormalities and Symptoms Among People With Patellofemoral Pain?

Background: Patellofemoral malalignment has been observed among people with patellofemoral pain (PFP) and may be associated with the presence of imaging features of osteoarthritis, symptoms, and function. Purpose: To determine whether patellofemoral joint alignment and bony shape are associated with (1) cartilage, bone, and soft tissue morphological abnormalities defined on magnetic resonance imaging (MRI) and (2) reported symptoms and function among people with PFP. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Participants (mean ± SD age, 30.2 ± 9.5 years; range, 14-50 years; 78 females, 58.6%) completed questionnaires regarding demographics, pain, symptoms, and function and underwent a 3-T MRI scan of their more symptomatic eligible knee. Structural MRI abnormalities were scored with the MOAKS (Magnetic Resonance Imaging Osteoarthritis Knee Score), and MRI alignment and shape were measured with standardized methods. Associations among MOAKS features, PFP symptoms, and alignment and shape measures were evaluated with regression analyses (α = .05). Results: Minor cartilage defects were present in 22 (16.5%) participants, patellar osteophytes in 83 (62.4%), anterior femur osteophytes in 29 (21.8%), Hoffa synovitis in 81 (60.9%), and prefemoral fat pad synovitis in 49 (36.8%). A larger Insall-Salvati ratio was significantly associated with the presence of patellar osteophytes (odds ratio [OR], 51.82; 95% CI, 4.20-640.01), Hoffa synovitis (OR, 60.37; 95% CI, 4.66-782.61), and prefemoral fat pad synovitis (OR, 43.31; 95% CI, 4.28-438.72) in the patellofemoral joint. A larger patellar tilt angle was significantly associated with the presence of minor cartilage defects (OR, 1.10; 95% CI, 1.00-1.20), the presence of patellar osteophytes (OR 1.12; 95%CI 1.02-1.22), and prefemoral fat pad synovitis (OR, 1.11; 95% CI, 1.03-1.20) in the patellofemoral joint. Finally, a larger bisect offset was significantly associated with the presence of minor cartilage defects (OR, 1.05; 95% CI, 1.00-1.11) and patellar osteophytes (OR, 1.07; 95% CI, 1.01-1.14) in the patellofemoral joint. The majority of patellofemoral alignment measures were not associated with symptoms or function. Conclusion: For people with PFP, the presence of morphological abnormalities defined on MRI appears to be related to particular patellofemoral alignment measures, including higher Insall-Salvati ratio (indicating patella alta), larger patellar tilt angle (indicating greater lateral tilt), and larger bisect offset (indicating greater lateral displacement). Hardly any associations were found with symptoms or function. So there might be a distinct subgroup of PFP that is more prone to developing patellofemoral osteoarthritis later in life, as particular alignment measures seem to be associated with the presence of patellar osteophytes. Prospective studies are required to investigate the longitudinal relationship between alignment or bony shape and morphological abnormalities defined on MRI in this patient population.

Ultrasonographic Morphological Changes in the Prefemoral Fat Pad Associated with Knee Osteoarthritis.

Background:In normal knees, quadriceps contraction changes the shape of the prefemoral fat pad (PFP). However, in persons with knee osteoarthritis (OA), the functional or morphological changes of the PFP are unclear. This study aimed to clarify the morphological changes in the PFP in individuals with knee OA through ultrasonography.Materials and Methods:Participants were divided into the OA (36 knees; mean age, 74 years), elderly (31 knees; mean age, 70 years), and young (26 knees; mean age, 21 years) groups. The anteroposterior (AP) length of the PFP before and during isometric quadriceps contraction at 0°, 30°, 60°, and 90° knee flexion was measured ultrasonographically. The difference between the maximum and minimum length values, change in length, was also measured. These parameters were compared among the three groups. In the OA group, correlations between the parameters and clinical features (knee pain; visual analog scale, knee range of motion [ROM], Kellgren and Lawrence (K/L) grade, and intercondylar distance) were examined by Spearman and Pearson's correlation coefficient tests.Results:The AP lengths of the PFP before contraction were significantly lower in the OA group than in elderly group and young group at 30° (6.9 ± 2.5 vs. 12.0 ± 3.6 or 11.1 ± 2.7 mm, respectively; in order P = 0.014, P = 0.006) and 60° (6.5 ± 2.0 vs. 9.7 ± 2.5 or 9.1 ± 2.7 mm, respectively; both P < 0.001). The AP lengths of the PFP during contraction were significantly lower in the OA group than in elderly group and young group at 0° (6.7 ± 2.3 vs. 8.8 ± 3.7 or 9.1 ± 1.6 mm, respectively; both P < 0.001), 30° (7.9 ± 2.6 vs. 12.9 ± 3.7 or 13.0 ± 2.6 mm, respectively; both P < 0.001), and 60° (7.1 ± 2.5 vs. 13.5 ± 2.6 or 13.6 ± 3.0 mm, respectively; both P < 0.001). The change in length before maximum isometric quadriceps contraction was significantly lower in the knee OA group than in both elderly and young groups (3.3 ± 1.9 vs. 8.4 ± 2.5 or 6.8 ± 3.0 mm, respectively; both P < 0.001). The change in length during contraction was also significantly lower in the knee OA group than in both the elderly and young groups (3.9 ± 2.3 vs. 8.7 ± 2.3 or 8.9 ± 2.0 mm, respectively; both P < 0.001). In the OA group, change in length during contraction was significantly associated with knee pain (r = −0.476, P = 0.007), knee ROM (r = 0.388, P = 0.019), and Kellgren and Lawrence grade (r = −0.357, P = 0.045).Conclusions:In knee OA, movement of PFP was decreased more than healthy participants. In the knee OA group, the decrease of the morphological change of the PFP showed the relationship between VAS score, knee extension ROM, intercondylar distance (ICD), and K/L grade. An evaluation to the PFP may be required in individuals with knee OA.

Imaging of traumatic injury and impingement of anterior knee fat

Fat is not just used by the body as bulk tissue. In addition to its role in storing energy and regulating hormone action, fat is used in some parts of the body for its mechanical properties. The anatomy of anterior knee fat is more complex than it appears at first sight and is capable of withstanding considerable compressive and shear stress. Specific lesions occur when such mechanical stress exceeds the physiological limits and are yet little known. Superficial fat can be the site of either acute injury by closed degloving called the Morel-Lavallée lesion or chronic injury, when subject to repeat excessive shear forces, due to more complex and less well-defined disruptions that result in pseudo-bursitis. There are three main anterior, intracapsular and extrasynovial fat pads in the knee joint, which are the infrapatellar fat pad (IFP) or Hoffa's fat pad, the quadriceps fat pad and the prefemoral fat pad. The IFP plays an important role as a mechanical shock absorber and guides the patella tendon and even the patella itself during flexion-extension movements. In response to repeated excessive stress, an inflammatory reaction and swelling of the IFP is first observed, followed by a fibrotic reaction with metaplastic transformation into fibrous, cartilaginous or bone tissue. More rarely, the two other deep fat pads (quadriceps and prefemoral) can, if subject to repeated stress, undergo similar restructuring inflammatory reactions with metaplasia resulting in tissue hardening, anterior pain and partial loss of function.

Elasticity of the prefemoral fat pad after total knee arthroplasty

Elasticity of the prefemoral fat pad after total knee arthroplasty

Changes of the prefemoral fat pad associated with knee osteoarthritis

Changes of the prefemoral fat pad associated with knee osteoarthritis

Knee X-rays

1. Know your knee anatomy See the anatomical landmarks on the diagrams below. Remember that the knees of younger children will look different, as the patella and ossification centres form. 2. Look for an effusion There are two fat pads in the knee the suprapatellar fat pad the prefemoral fat pad Make sure they are… Read More »Knee X-rays

MRI of the knee in asymptomatic adolescent swimmers: a controlled study

BackgroundSwimming is a widespread sporting activity generally regarded as an ideal form of exercise, which has little or no impact on the knees. However, overuse or repetitive microtrauma injuries may...

Prefemoral fat pad: impingement and a mass-like protrusion on the lateral femoral condyle causing mechanical symptoms

We describe a case of prefemoral fat pad impingement between the anterior aspect of the distal femur and the patella undersurface, and a mass-like fatty tissue protrusion on the lateral femoral condyle that caused mechanical symptoms.

Inflammation of Hoffa’s fat pad in the setting of HIV: magnetic resonance imaging findings in six patients

To describe MR imaging findings of inflammation of Hoffa's fat pad as a cause of nonspecific knee pain in the HIV-infected population. Retrospective review. A retrospective review of 400 consecutive MR imaging studies of the knee performed at two institutions over a six-month period was conducted. Inclusion criteria included HIV infection in conjunction with diffuse high signal intensity throughout Hoffa's fat pad on fluid sensitive sequences. Medical histories and images were reviewed by two musculoskeletal radiologists. Exclusion criteria included post-surgical changes, internal derangement, and/or changes consistent with an active synovial inflammatory process. Seven HIV-infected subjects with non-specific knee pain were identified, six of whom met imaging inclusion criteria. Findings in Hoffa's fat pad were present in nine MR studies (bilateral in three, and unilateral in three subjects). Other findings include bilateral enlargement of Hoffa's fat pad in one subject, global increase in signal intensity of the suprapatellar fat pad on fluid sensitive sequences in three subjects and of the prefemoral fat pad in four subjects, avascular necrosis in one subject, and a diffuse pattern of patchy bone marrow edema in one subject. Subjects were diagnosed with HIV from 1993-1999, with imaging performed in 2005. Subjects were on HAART medication for an indeterminate, extended duration of time prior to imaging. CD4 levels of subjects ranged from 448-1262 cells/muL (X=727.33 cells/muL). While the MR imaging findings of diffuse inflammation of Hoffa's fat pad are nonspecific and unclear in etiology, an association with HIV may exist.

Quadriceps fat pad signal intensity and enlargement on MRI: prevalence and associated findings.

The purpose of this investigation was to characterize the MRI appearance of the quadriceps fat pad and to correlate the findings with other knee abnormalities, anatomic measurements of the extensor mechanism, and findings from history and at physical examination. Ninety-two consecutive knee MRI examinations from 84 patients were retrospectively reviewed by two musculoskeletal radiologists for quadriceps fat pad enlargement and signal intensity. Other data from the retrospective review included infrapatellar and prefemoral fat pad signal intensity, quadriceps and patellar tendon abnormalities, joint effusion, medial plica, chondromalacia, articular muscle thickness, and prepatellar edema. The patellar length, patellar articular length, patellar tendon length, and femoral sulcus angle were measured. MRI reports were reviewed for meniscal and ligament abnormalities. Clinical data were reviewed for findings of anterior knee pain in the history and at physical examination. The chi-square and Student's t tests were used to determine significant associations. Twelve percent (11/92) of MRI examinations showed quadriceps fat pad mass effect on the suprapatellar recess, which was associated with intermediate or fluid signal intensity of the quadriceps fat pad (chi(2) = 7.19, p = 0.0274) but with no other findings on knee MRI. Anterior knee pain at physical examination was associated with quadriceps fat pad mass effect (chi(2) = 8.76, p = 0.0031), medial collateral ligament abnormality (chi(2) = 4.83, p = 0.0031), and history of anterior knee pain (chi (2) = 22.76, p < 0.0001). Enlargement of the quadriceps fat pad on MRI has a prevalence of 12% and is significantly associated with intermediate or fluid signal intensity of the quadriceps fat pad and anterior knee pain.

MR imaging of the knee: can changes in the intracapsular fat pads be used as a sign of synovial proliferation in the presence of an effusion?

Synovial proliferation is difficult to detect on MR images when joint effusions are present. The objective of this study was to assess the efficacy of MR changes in intracapsular fat pads (prefemoral, quadriceps, Hoffa's) as a sign of synovial proliferation in patients with knee effusions. MR images were obtained in 70 patients with knee effusions. An effusion was considered present if the suprapatellar bursa was distended 1 cm in anterior to posterior diameter on T2-weighted sagittal images. The experimental group consisted of 32 patients with proliferative effusions (effusions associated with synovial proliferation) diagnosed on the basis of histologic or microbiologic data or strict rheumatologic criteria. This group comprised 11 patients with pigmented villonodular synovitis, six with rheumatoid arthritis, one with psoriatic arthritis, three with hemosideric arthritis, and 11 with septic arthritis. The control group comprised 38 subjects with knee effusions who had no arthroscopic evidence of synovial proliferation. After determining the MR criteria of proliferative effusion, two observers who had no knowledge of these cases evaluated abnormalities of the intracapsular fat pads seen on sagittal intermediate-weighted midline MR images. Characteristic changes in the fat pads were noted on MR images in patients with proliferative synovial effusions. Scalloping or truncation of the prefemoral fat pad was 77% sensitive and 95% specific as a predictor of proliferative effusion. Defects and displacement of Hoffa's fat pad had a sensitivity of 57% and a specificity of 99%, and nonvisualization or irregular margins of the quadriceps fat pad had a sensitivity of 61% and a specificity of 100%. Characteristic changes in intracapsular fat pads seen on MR images of patients with proliferative effusions can help distinguish these patients from those with effusions without synovial proliferation.