Patellofemoral Pain : Where does the pain come from?

My thesis is about patellofemoral pain (PFP), a common knee complaint among physically active young individuals. It is also known as ’anterior knee pain’, ’retropatellar chondropathy’ or more recently suggested ‘theatre or moviegoers knee’. PFP is characterized by retropatellar pain (behind the kneecap) or peripatellar pain (around the kneecap), specifically during knee loading activities, like running, cycling, squatting, stair climbing, and/or during prolonged sitting with the knees flexed in 90 degrees. The majority of people with PFP are treated conservatively with exercise therapy, but the effect of exercise therapy is still unknown. Therefore, this thesis assessed the effects of exercise therapy and aimed to point out the most effective exercise strategy. However, despite the application of a variety of treatment modalities, a substantial group of patients has persistent complaints. The pathophysiology of PFP is considered to be multifactorial, but still widely unknown. Therefore, emphasis has been placed on unraveling the pathophysiology of PFP with advanced MRI techniques. For years it has been suggested that cartilage plays an important role, but this thesis suggests otherwise. Furthermore, an innovative MRI method was developed to study blood perfusion of the patella. It might be that vascular problems are present in patients with knee pain during watching a movie or visiting the theatre in particular. Or maybe, there are no differences between patients and control subjects on MRI, but only differences in pain perception as has been suggested previously......

Patellofemoral alignment and geometry and early signs of osteoarthritis are associated in patellofemoral pain population

Background: Patellofemoral pain (PFP) patients show increased prevalence of patellar malalignment. Structural and alignment abnormalities of the patellofemoral joint (PFJ) may play a role in development of PFP and patellofemoral osteoarthritis (PFOA). Objectives: Evaluating associations of patellofemoral alignment and femoral geometry with bony and cartilaginous abnormalities in PFP patients and healthy control subjects. Methods: Data from a case-control study were used (64 PFP subjects, 70 control subjects, 57% female, age 23.2 (6.4)). Alignment and femoral geometry measu

Quantitative DCE-MRI demonstrates increased blood perfusion in Hoffa’s fat pad signal abnormalities in knee osteoarthritis, but not in patellofemoral pain

Objective: Infrapatellar fat pad (IPFP) fat-suppressed T2 (T2FS) hyperintense regions on MRI are an important imaging feature of knee osteoarthritis (OA) and are thought to represent inflammation. These regions are also common in non-OA subjects, and may not always be linked to inflammation. Our aim was to evaluate quantitative blood perfusion parameters, as surrogate measure of inflammation, within T2FS-hyperintense regions in patients with OA, with patellofemoral pain (PFP) (supposed OA precursor), and control subjects. Methods: Twenty-two knee OA patients, 35 PFP patients and 43 healthy controls were included and underwent MRI, comprising T2 and DCE-MRI sequences. T2FS-hyperintense IPFP regions were delineated and a reference region was drawn in adjacent IPFP tissue with normal signal intensity. After fitting the extended Tofts pharmacokinetic model, quantitative DCE-MRI perfusion parameters were compared between the two regions within subjects in each subgroup, using a paired Wilcoxon signed-rank test. Results: T2FS-hyperintense IPFP regions were present in 16 of 22 (73%) OA patients, 13 of 35 (37%) PFP patients, and 14 of 43 (33%) controls. DCE-MRI perfusion parameters were significantly different between regions with and without a T2FS-hyperintense signal in OA patients, demonstrating higher Ktrans compared to normal IFPF tissue (0.039 min−1 versus 0.025 min−1, p = 0.017) and higher Ve (0.157 versus 0.119, p = 0.010). For PFP patients and controls no significant differences were found. Conclusions: IPFP T2FS-hyperintense regions are associated with higher perfusion in knee OA patients in contrast to identically appearing regions in PFP patients and controls, pointing towards an inflammatory pathogenesis in OA only. Key Points: • Morphologically identical appearing T2FS-hyperintense infrapatellar fat pad regions show different perfusion in healthy subjects, subjects with patellofemoral pain, and subjects with knee osteoarthritis. • Elevated DCE-MRI perfusion parameters within T2FS-hyperintense infrapatellar fat pad regions in patients with osteoarthritis suggest an inflammatory pathogenesis in osteoarthritis, but not in patellofemoral pain and healthy subjects

Quantitative volume and dynamic contrast-enhanced MRI derived perfusion of the infrapatellar fat pad in patellofemoral pain

Background: Patellofemoral pain (PFP) is a common knee condition and possible precursor of knee osteoarthritis (OA). Inflammation, leading to an increased perfusion, or increased volume of the infrapatellar fat pad (IPFP) may induce knee pain. The aim of the study was to compare quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters, as imaging biomarkers of inflammation, and volume of the IPFP between patients with PFP and controls and between patients with and without IPFP edema or joint effusion. Methods: Patients with PFP and healthy controls were included and underwent non-fat suppressed 3D fast-spoiled gradient-echo (FSPGR) and DCE-MRI. Image registration was applied to correct for motion. The IPFP was delineated on FSPGR using Horos software. Volume was calculated and quantitative perfusion parameters were extracted by fitting extended Tofts' pharmacokinetic model. Differences in volume and DCE-MRI parameters between patients and controls were tested by linear regression analyses. IPFP edema and effusion were analyzed identically. Results: Forty-three controls and 35 PFP patients were included. Mean IPFP volume was 26.04 (4.18) mL in control subjects and 27.52 (5.37) mL in patients. Median Ktrans was 0.017 (0.016) min-1 in control subjects and 0.016 (0.020) min-1 in patients. None of the differences in volume and perfusion parameters were statistically significant. Knees with effusion showed a higher perfusion of the IPFP compared to knees without effusion in patients only. Conclusions: The IPFP has been implicated as source of knee pain, but higher DCE-MR blood perfusion, an imaging biomarker of inflammation, and larger volume are not associated with PFP. Patient's knees with effusion showed a higher perfusion, pointing towards inflammation

Quantitative subchondral bone perfusion imaging in knee osteoarthritis using dynamic contrast enhanced MRI

Objective: Subchondral bone changes, characterized by increased bone turnover and vascularity, are believed to stimulate progression and pain in knee osteoarthritis (OA). The objective of this study was to evaluate the bone perfusion in knee OA using quantitative dynamic contrast enhanced MRI (DCE-MRI). Design: Unicompartmental knee OA patients were included and underwent 3 Tesla DCE-MRI and T2-weighted MRI. Quantitative DCE-MRI analysis of Ktrans and Kep, representing perfusion parameters, was performed to evaluate differences between the most and least affected knee compartment. First, DCE-MRI parameter differences between epimetaphyseal and subchondral bone in both femur and tibia were assessed. Second, DCE-MRI parameters in subchondral bone marrow lesions (BMLs) were compared to surrounding subchondral bone without BMLs. Results: Twenty-three patients were analyzed. Median Ktrans and Kep in epimetaphyseal bone were significantly higher (p < 0.05) in the most affected (Ktrans: 0.014; Kep: 0.054 min−1) compared to least affected (Ktrans: 0.010; Kep: 0.016 min−1) compartment. For subchondral bone, DCE-MRI parameters were significantly higher (p < 0.05) in the most affected (Ktrans: 0.019; Kep: 0.091 min−1) compared to least affected (Ktrans: 0.014; Kep: 0.058 min−1) compartment as well. Subchondral BMLs detected on fat-saturated T2-weighted images were present in all patients. Median Ktrans (0.091 vs 0.000 min−1) and Kep (0.258 vs 0.000 min−1) were significantly higher within subchondral BMLs compared to surrounding subchondral bone without BMLs (p < 0.001). Conclusions: Increased perfusion parameters in epimetaphyseal bone, subchondral bone and BMLs are observed in unicompartmental knee OA. BMLs likely account for most of the effect of the higher bone perfusion in knee OA

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.

Blood perfusion of patellar bone measured by dynamic contrast-enhanced MRI in patients with patellofemoral pain: A case-control study

Background: Altered perfusion might play an important role in the pathophysiology of patellofemoral pain (PFP), a common knee complaint with unclear pathophysiology. Purpose: To investigate differences in dynamic contrast-enhanced (DCE)-MRI perfusion parameters between patients with PFP and healthy control subjects. Population/Subjects/Phantom/Specimen

Characteristics and outcome of patellofemoral pain in adolescents: Do they differ from adults?

Study Design: Case series with 1-year follow-up. Background: Most of the recommendations for the diagnosis, treatment, and prognosis of patellofemoral pain (PFP) are based on research performed in adults. The literature suggests that there are potential differences between adolescents and adults with PFP. OBJECTIVES: To investigate differences in characteristics, symptoms, and prognosis at 1-year follow-up between adolescents and adults with PFP. Methods: Data from 64 patients with PFP, assessed at baseline and 1-year follow-up, were used. At baseline, data on demographics, symptoms, and coping strategies were obtained by questionnaire. Physical examination included strength and flexibility measurements of the quadriceps and hamstrings. At 1-year follow-up, a questionnaire was used to collect data on pain, function, and recovery. Differences between adolescents (14-18 years) and adults (18-40 years) were analyzed using regression techniques, adjusted for sex, body mass index, and the presence of bilateral pain. Results: Of the 64 patients with PFP included at baseline, 78.1% were available for follow-up. At baseline, adolescents with PFP had a significantly lower body mass index (20.7 versus 24.9 kg/m2) and a greater percentage of bilateral pain (70% versus 43.2%) than adults with PFP. There were no differences in reported pain and symptoms between the 2 groups. In total, 25% of the adolescents regarded themselves as recovered after 1 year, compared to 22.7% of the adults (adjusted P = .725). Conclusion: The sample size of the study, in relation to the number of statistical tests performed, urges caution in the interpretation of the results. In contrast to what has been suggested previously, only minor differences seem to exist between adolescents and adults with PFP. In both groups, PFP is clearly not a self-limiting disease, with nearly 75% of those in this study reporting persistent pain at 1-year follow-up. Level of Evidence: Prognosis, level 4

The development of cam-type deformity in adolescent and young male soccer players

Background: Cam impingement is a well-recognized cause of hip pain and might cause osteoarthritis of the hip. Clinically, cam impingement is mostly observed in young, active male patients, but only a few studies have focused on the manifestation of cam-type deformities during skeletal development.Purpose: To determine the age of onset and prevalence of cam-type deformities in young male soccer players versus controls.Study Design: Cross-sectional study; Level of evidence, 3.Methods: In this study, 89 elite preprofessional soccer players and 92 controls aged 12 to 19 years were included. In the soccer players, range of motion and impingement tests were performed. Both an anteroposterior (AP) pelvic radiograph and a frog-leg lateral radiograph of the hip were obtained according to a standardized protocol. Controls with both an AP pelvic and a frog-leg lateral radiograph and no hip disorders were obtained from radiology databases. The α angle was automatically determined in all radiographs, using a threshold value of 60°to define a cam-type deformity. Further, all radiographs were scored using a 3-point scoring system. The anterosuperior head-neck junction was classified as (1) normal, (2) flattened, or (3) having a prominence. Differences in prevalence were tested using logistic regression. Differences in range of motion were calculated using generalized estimating equations.Results: An α angle >60°was already found at the age of 12 years in some soccer players and controls. A cam-type deformity defined by α angle tended to be more prevalent in soccer players (26%) than in controls (17%; P =.31). In 13% of soccer players, a prominence was visible on radiographs and was first seen at the age of 13 years. The anterosuperior flattening (56% vs 18%, P =.0001) and prominence (13% vs 0%, P <.03) were more prevalent in soccer players than in controls.Conclusion: Cam-type deformities were recognizable and present from the age of 13 years and were more prevalent in soccer players than in their nonathletic peers. Cam-type deformity develops during adolescence and is likely to be influenced by high-impact sports practice