Diffusely increased bone scintigraphic uptake in patellofemoral pain syndrome

Effectiveness of an educational approach between adolescents and adults with patellofemoral pain syndrome: a scoping review with meta-analysis

[Purpose] This study aimed to compare the effectiveness of an educational approach between adolescents and adults with patellofemoral pain syndrome. [Participants and Methods] The PROSPERO protocol number is CRD42022362680. Four databases (PubMed, CINAHL, Scopus, Cochrane) were searched. Randomized control trials on the effectiveness of the educational approach for patellofemoral pain syndrome were compared between adolescents and adults. Two investigators independently screened eligible studies. Two randomized control trials proceeded through meta-analysis with a visual analogue scale in the mid-term (from 18 weeks to 6 months). [Results] The meta-analysis results indicated that no significant difference was observed between education and combined education with exercise. A tendency to improve in the intervention of combined education with exercise for adolescents was noted, whereas no effect of education for adults was observed. [Conclusion] Treatment strategies combining education with exercise for patellofemoral pain syndrome may differ between adolescents and adults.

Effect of hip abductors and lateral rotators' muscle strengthening on pain and functional outcome in adult patients with patellofemoral pain: A systematic review and meta-analysis

BACKGROUND

Even though literature indicates presence of weak hip abductors and lateral rotators' in Patellofemoral Pain (PFP), studies evaluating the effect of hip abductors and lateral rotators strengthening to improve knee function and quality of life in PFP are limited.

OBJECTIVE

This study systematically reviews and meta-analyzes the best evidence on the therapeutic value of strengthening hip abductors and lateral rotators muscles for treating PFP with a presumptive hypothesis that strengthening hip muscles stabilizes the patellofemoral joint, relieves pain, and enhances knee functions.

METHOD

Medline, EMBASE, CINAHL, PEDro and PubMed Central databases were searched between January 1994 and September 2019 using the PICOS tool. The methodological quality of the selected studies were appraised individually using the 20-item McMaster Critical Review Form for Quantitative Studies. Supplemental quality appraisal of randomized controlled clinical trials performed using the Cochrane Collaboration's 'Risk of bias' quality criteria. Data on patient population demographics, interventions, duration of intervention, and outcome measures were extracted and summarized in evidence tables and descriptive analysis. Meta-analyses under both fixed and random-effects models determined pooled effects size from appropriate RCTs.

RESULTS

All fourteen studies demonstrated that hip muscle strengthening improved pain and knee function. All RCTs, except one, demonstrated that hip muscle strengthening is superior to quadriceps strengthening. Of the five RCTs assessing the additional effect of hip-quad versus quadriceps strengthening, four suggested that hip-quad strengthening is superior to standard quadriceps strengthening alone to improve PFP and knee function.

CONCLUSION

In adult patients with PFP, strengthening hip abductors and lateral rotators' have beneficial therapeutic effects than the conventional quadriceps exercises in improving knee pain and function both in the short- and long term. However, the present review data can be used to develop a standardized hip-quad protocol in the future.

Load-deformation characteristics of cadaver patellae: Relationship to intraosseous pressure

BACKGROUND

Anterior knee pain can arise from several sources. One of the main sources of pain in patients with anterior knee pain is the patella. Increased patellofemoral joint loading is the prime source of patellar pain. Elevated intraosseous pressures have been measured in painful patellae and increasing the intraosseous fluid pressure in the patella causes pain. Whether elevated fluid pressure is an independent source of pain or if the patellar deformation under load leads to elevated pressure and pain has not been determined. Our hypothesis was that the patella deforms measurably under physiologic loads and that intraosseous pressure increase is related to that deformation. The relationship may be linear as measured by correlation or nonlinear as measured by the sum of squared error.

METHODS

Part I: Assessment of patellar load-deformation profiles were obtained in 2 intact cadaver patellae and 1 bisected patella under physiologic loads. Part II: Measurements of intraosseous pressure were obtained in 9 cadaver patellae as the patellae were compressed with physiologic loads. Pressures were recorded at sequential levels of anterior-posterior patellar compression.

FINDINGS

Cadaver patellae compress up to 3.5 mm in the anterior-posterior plane. Compression with physiologic forces raises intraosseous pressure to more than 40 mmHg.

INTERPRETATION

Load-deformation of cadaver patellae results in deformation and an increase in intraosseous pressure. These findings may help explain previous studies of patellofemoral pain where elevated patellar intraosseous pressures have been found in vivo.

Contributions of nuclear medicine in paediatric non-tumour musculoskeletal pathology

Non-tumour musculoskeletal pathology in children represents a high percentage of the nuclear medicine studies requested by paediatricians. As these are immature bones and joints, in constant growth and remodelling, they present their own physiological and anatomical peculiarities that require a specific management for the paediatric age group. Using different clinical scenarios frequently observed in medical appointments (limping, back pain or fever, among others), we have summarised the possible findings or artefacts that can be obtained in the different Nuclear Medicine explorations, including bone scintigraphy and hybrid images such as PET/CT. To obtain high quality images requires careful attention to technique and positioning in children. Bone scintigraphy is a common paediatric nuclear medicine procedure and plays an important role in the diagnosis of musculoskeletal pathologies and can be complemented by techniques such as SPECT to improve localisation and diagnostic accuracy. In addition, ¹⁸F-FDG PET/CT is increasingly applied in the evaluation of children. This article reviews the usual indications of, mainly, bone scintigraphy and ¹⁸F-FDG PET/CT in paediatric non-tumour musculoskeletal diseases, how to interpret them properly, being essential to know the normal physiological distribution of each radiopharmaceutical, as well as the common variants of paediatric growth that can simulate disease, implying possible misinterpretations between normal and pathological structures.

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/ANIMAL MODEL

Thirty-five adult patients with PFP and 44 healthy adult control subjects.

FIELD STRENGTH/SEQUENCE

3T DCE-MRI consisting of a sagittal, anterior-posterior, frequency-encoded, fat-suppressed 3D spoiled gradient-echo sequence with intravenous contrast administration.

ASSESSMENT

Patellar bone volumes of interest (VOIs) were delineated by a blinded observer. Quantitative perfusion parameters (k_ep and k_trans ) were calculated from motion-compensated DCE-MRI data by fitting Tofts' model. Weighted mean and unweighted median values of k_ep and k_trans were computed within the patellar bone VOIs.

STATISTICAL TESTS

Differences in patellar bone perfusion parameters were compared between groups by linear regression analyses, adjusted for confounders.

RESULTS

Mean differences of weighted mean and unweighted median were 0.0039 (95% confidence interval [CI] -0.0013; 0.0091) and 0.0052 (95% CI -0.0078; 0.018) for k_trans , and 0.046 (95% CI -0.021; 0.11) and 0.069 (95% CI -0.017; 0.15) for k_ep , respectively. All perfusion parameters were not significantly different between groups (P-values: 0.32; 0.47 for k_trans , and 0.24; 0.15) for k_ep . However, a significant difference in variance between populations was observed for k_trans (P-value 0.007).

DATA CONCLUSION

Higher patellar bone perfusion parameters were found in patients with PFP when compared to healthy control subjects, but these differences were not statistically significant. This result, and the observed significant difference in k_trans variance, warrant further research.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1344-1350.

Dynamic contrast-enhanced MRI of the patellar bone: How to quantify perfusion

Purpose

To identify the optimal combination of pharmacokinetic model and arterial input function (AIF) for quantitative analysis of blood perfusion in the patellar bone using dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI).

Materials and Methods

This method design study used a random subset of five control subjects from an Institutional Review Board (IRB)‐approved case–control study into patellofemoral pain, scanned on a 3T MR system with a contrast‐enhanced time‐resolved imaging of contrast kinetics (TRICKS) sequence. We systematically investigated the reproducibility of pharmacokinetic parameters for all combinations of Orton and Parker AIF models with Tofts, Extended Tofts (ETofts), and Brix pharmacokinetic models. Furthermore, we evaluated if the AIF should use literature parameters, be subject‐specific, or group‐specific. Model selection was based on the goodness‐of‐fit and the coefficient of variation of the pharmacokinetic parameters inside the patella. This extends previous studies that were not focused on the patella and did not evaluate as many combinations of arterial and pharmacokinetic models.

Results

The vascular component in the ETofts model could not reliably be recovered (coefficient of variation [CV] of v_p >50%) and the Brix model parameters showed high variability of up to 20% for k_el across good AIF models. Compared to group‐specific AIF, the subject‐specific AIF's mostly had higher residual. The best reproducibility and goodness‐of‐fit were obtained by combining Tofts' pharmacokinetic model with the group‐specific Parker AIF.

Conclusion

We identified several good combinations of pharmacokinetic models and AIF for quantitative analysis of perfusion in the patellar bone. The recommended combination is Tofts pharmacokinetic model combined with a group‐specific Parker AIF model.

Level of Evidence: 2

Technical Efficacy: Stage 1

J. Magn. Reson. Imaging 2018;47:848–858.

Distribution and symmetrical patellofemoral pain patterns as revealed by high-resolution 3D body mapping: a cross-sectional study

Background

Detailed pain mapping of extent and distribution in individuals with patellofemoral pain (PFP) within and around a complex structure such as the knee has yet to be explored.

Methods

Perceptions of on-going pain from adolescents and young adults (N = 35) with long-standing (>10 months) PFP were collected on high-resolution 3D digital body-schema of the knees. Location, area of pain, pain intensity, laterality, worse side of knee pain, symptom duration, and symmetry in bilateral knee pain were recorded. A threshold for naturally occurring variations in symmetrical knee pain drawings were collected from 18 healthy controls and used in combination with the development a symmetry index (0–1) to create a fuzzy rule for classifying symmetrical and non-symmetrical PFP patterns as compared to a PFP expert. The symmetry index was computed and tested using a correlation coefficient alone or in combination with the Jaccard index and the true and false positive rates (TPR and FPR, respectively) determined.

Results

The peripatellar region was the common report of pain location however, novel and nonconforming PFP patterns were identified and the majority of individuals (22 of 27) with bilateral PFP expressed highly-symmetric mirror-image pain. Individuals with symptom duration of 5 years or more had a greater area of pain, compared to those with symptoms for less than 5 years. The total area of pain was correlated to symptom duration for those with extended symptoms durations and a progression towards an “O” shaped pattern emerged. A TPR of 100% for identifying symmetrical knee pain patterns was found however the expert PFP tended to be stricter, as reflected in FPR of 20%.

Conclusions

A high proportion of PFP patterns or symptoms occur in mirrored locations and are exceptionally symmetrical, and long duration of symptoms appear to converge to an ‘O’ shape. Classifying symmetrical pain patterns is subjective however simple fuzzy rules and correlations can be used to increase objectivity. This study highlights a gap in knowledge of PFP symptom presentation, reveals what may be a natural progression of symptoms, and provides valuable clinical insight for both pain management and treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1521-5) contains supplementary material, which is available to authorized users.

The SPECT/CT Evaluation of Compartmental Changes after Open Wedge High Tibial Osteotomy

Purpose

The purpose of this study was to evaluate compartmental changes using combined single-photon emission computerized tomography and conventional computerized tomography (SPECT/CT) after open wedge high tibial osteotomy (OWHTO) for providing clinical guidance for proper correction.

Materials and Methods

Analysis was performed using SPECT/CT from around 1 year after surgery on 22 patients who underwent OWHTO. Postoperative mechanical axis was measured and classified into 3 groups: group I (varus), group II (0°–3° valgus), and group III (>3° valgus). Patella location was evaluated using Blackburne-Peel (BP) ratio. On SPECT/CT, the knee joint was divided into medial, lateral, and patellofemoral compartments and the brighter signal was marked as a positive signal.

Results

Increased signal activity in the medial compartment was observed in 12 cases. No correlation was observed between postoperative mechanical axis and medial signal increase. Lateral increased signal activity was observed in 3 cases, and as valgus degree increased, lateral compartment’s signal activity increased. Increased signal activity of the patellofemoral joint was observed in 7 cases, and significant correlation was observed between changes in BP ratio and increased signal activity.

Conclusions

For the treatment of medial osteoarthritis, OWHTO requires overcorrection that does not exceed 3 valgus. In addition, the possibility of a patellofemoral joint problem after OWHTO should be kept in mind.

Evaluation of Knee Pain in Athletes: A Radiologist's Perspective

Lower limb injuries account for most of all injuries suffered by athletes and the knee joint accounts for over half of these. The etiology of knee pain is multifactorial; a good history focusing on the mechanism of injury and the chronicity of pain is extremely useful in correlating with radiologic findings and establishing a clinically meaningful diagnosis. This review article will discuss several important and common causes of acute and chronic knee pain in athletes, focusing on their mechanism of injury and site of pain as well as their salient imaging findings.

(18)F-Sodium Fluoride PET-CT Hybrid Imaging of the Lumbar Facet Joints: Tracer Uptake and Degree of Correlation to CT-graded Arthropathy

We aim to evaluate ¹⁸F-NaF uptake by facet joints with hybrid PET-CT technique. Specifically, we evaluate NaF uptake in the facet joints of the lower lumbar spine, and correlate with the morphologic grade of facet arthropathy on CT. 30 consecutive patients who underwent standard vertex to toes NaF PET-CT for re-staging of primary neoplastic disease without measurable or documented bony metastases were identified. Maximum (SUVmax) and average (SUVavg) standardized uptake values were calculated for each L3-4, L4-5, and L5-S1 facet joint (n = 180) and normalized to average uptake in the non-diseased femur. A Pathria grade (0-3) was assigned to each facet based upon the CT morphology. Spearman's rank correlation was performed for normalized SUVmax and SUVavg with Pathria grade. ANOVA was performed with Tukey-Kramer pairwise tests to evaluate differences in uptake between Pathria groups. Facet normalized SUVmax (r = 0.31, P < 0.001) and SUVavg (r = 0.28, P < 0.001) demonstrated a mild positive correlation with CT Pathria grade. There was a wide range of uptake values within each Pathria grade subgroup with statistically significant differences in uptake only between Pathria grade 3 as compared to grades 0, 1, and 2. In conclusion, NaF uptake and morphologic changes of the facet joint on CT are weakly correlated. Physiologic information provided by NaF uptake is often discrepant with structural findings on CT suggesting NaF PET may supplement conventional structural imaging for identification of pain generating facet joints. Prospective investigation into the relationship of facet joint NaF uptake with pain and response to pain interventions is warranted.

Value of SPECT-CT Imaging for Middle-Aged Patients with Chronic Anterior Knee Pain

Background

Single-photon emission computed tomography-computed tomography (SPECT-CT) is a highly sensitive tool for detecting bone metabolism. We determined whether subchondral bone metabolism, as indicated by SPECT-CT in the patellofemoral (PF) joint, predicts response to conservative management in middle-aged patients with chronic anterior knee pain (AKP), and whether SPECT-CT results correlate with arthroscopic assessments of chondral lesions in the PF joint.

Methods

The study group comprised 74 middle-aged patients with chronic AKP. All of the patients underwent SPECT-CT, and the results were graded along a scale of 0 to 3°. After 8 weeks of conservative management, they were grouped as responders (n = 40) or non-responders (n = 34) according to symptom improvement. We compared the median scintigraphic uptake of the PF joint between the two groups, and evaluated the positive predictive value (PPV) of uptake for treatment response in each patient. In non-responders, cartilage condition was assessed during arthroscopy, and the correlation of scintigraphic uptake with severity of the chondral lesion was assessed.

Results

The median scintigraphic uptake in the patella was higher in non-responders than in responders (2 vs. 1). Among patients with higher patella uptake (grade 2 or 3), the PPV for non-response to conservative therapy was 62–67 %, whereas it was 24–25 % in patients with lower uptake (grade 0 or 1). Patella uptake corresponded strongly with arthroscopic assessment of patellar chondral lesions; the correlation was less strong for the femoral trochlea.

Conclusions

Increased subchondral bone metabolism in the patella is associated with responsiveness to conservative therapy. SPECT-CT can benefit clinicians by predicting the treatment response from conservative management.

Influence of step rate and quadriceps load distribution on patellofemoral cartilage contact pressures during running

Interventions used to treat patellofemoral pain in runners are often designed to alter patellofemoral mechanics. This study used a computational model to investigate the influence of two interventions, step rate manipulation and quadriceps strengthening, on patellofemoral contact pressures during running. Running mechanics were analyzed using a lower extremity musculoskeletal model that included a knee with six degree-of-freedom tibiofemoral and patellofemoral joints. An elastic foundation model was used to compute articular contact pressures. The lower extremity model was scaled to anthropometric dimensions of 22 healthy adults, who ran on an instrumented treadmill at 90%, 100% and 110% of their preferred step rate. Numerical optimization was then used to predict the muscle forces, secondary tibiofemoral kinematics and all patellofemoral kinematics that would generate the measured primary hip, knee and ankle joint accelerations. Mean and peak patella contact pressures reached 5.0 and 9.7MPa during the midstance phase of running. Increasing step rate by 10% significantly reduced mean contact pressures by 10.4% and contact area by 7.4%, but had small effects on lateral patellar translation and tilt. Enhancing vastus medialis strength did not substantially affect pressure magnitudes or lateral patellar translation, but did shift contact pressure medially toward the patellar median ridge. Thus, the model suggests that step rate tends to primarily modulate the magnitude of contact pressure and contact area, while vastus medialis strengthening has the potential to alter mediolateral pressure locations. These results are relevant to consider in the design of interventions used to prevent or treat patellofemoral pain in runners.

Holistic approach to understanding anterior knee pain. Clinical implications

Anterior knee pain is one of the most frequent reasons for consultation within knee conditions. The aetiology is not well known, which explains the sometimes unpredictable results of its treatment. Normally, when we see a patient in the office with anterior knee pain, we only study and focus on the knee. If we do this, we are making a big mistake. We must not forget to evaluate the pelvis and proximal femur, as well as the psychological factors that modulate the course of the illness. Both the pelvifemoral dysfunction as well as the psychological factors (anxiety, depression, catastrophization and kinesiophobia) must be included in our therapeutic targets of the multidisciplinary treatment of anterior knee pain. We must not only focus on the knee, we must remember to "look up" to fully understand what is happening and be able to solve this difficult problem. The aetiology of anterior knee pain is multifactorial. Therefore, diagnosis and treatment of patellofemoral disorders must be individualized. Our findings stress the importance of tailoring physiotherapy, surgery and psycho-educational interventions to each patient.

Running-induced patellofemoral pain fluctuates with changes in patella water content

Although increased bone water content resulting from repetitive patellofemoral joint loading has been suggested to be a possible mechanism underlying patellofemoral pain (PFP), there is little data to support this mechanism. The purpose of the current study was to determine whether running results in increases in patella water content and pain and whether 48 hours of rest reduces patella water content and pain to pre-running levels. Ten female runners with a diagnosis of PFP (mean age 25.1 years) participated. Patella water content was quantified using a chemical-shift-encoded water-fat magnetic resonance imaging (MRI) protocol. The visual analog scale (VAS) was used to quantify subjects' pain levels. MRI and pain data were obtained prior to running, immediately following a 40-minute running session, and 48 hours post-running. Pain and patella water content were compared among the 3 time points using one-way ANOVA's with repeated measures. Immediately post-running, persons with PFP reported significant increases in pain and exhibited elevated patella water content. Pain and patella water content decreased to pre-running levels following 48 hours of rest. Our findings suggest that transient changes in patella water content associated with running may, in part, contribute to patellofemoral symptoms.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

Comparison of MRI and ¹⁸F-NaF PET/CT in patients with patellofemoral pain

PURPOSE

To determine whether bone metabolic activity corresponds to bone and cartilage damage in patients with patellofemoral pain.

MATERIALS AND METHODS

We acquired magnetic resonance imaging (MRI) and (18) F-NaF positron emission tomography (PET) / computed tomography (CT) scans of the knees of 22 subjects. We compared locations of increased tracer uptake on the (18) F-NaF PET images to bone marrow edema and cartilage damage visualized on MRI.

RESULTS

We found that increased bone activity on (18) F-NaF PET does not always correspond to structural damage in the bone or cartilage as seen on MRI.

CONCLUSION

Our results suggest that (18) F-NaF PET/CT may provide additional information in patellofemoral pain patients compared to MRI.

Patients with patellofemoral pain exhibit elevated bone metabolic activity at the patellofemoral joint

Patellofemoral pain is characterized by pain behind the kneecap and is often thought to be due to high stress at the patellofemoral joint. While we cannot measure bone stress in vivo, we can visualize bone metabolic activity using (18) F NaF PET/CT, which may be related to bone stress. Our goals were to use (18) F NaF PET/CT to evaluate whether subjects with patellofemoral pain exhibit elevated bone metabolic activity and to determine whether bone metabolic activity correlates with pain intensity. We examined 20 subjects diagnosed with patellofemoral pain. All subjects received an (18) F NaF PET/CT scan of their knees. Uptake of (18) F NaF in the patella and trochlea was quantified by computing the standardized uptake value and normalizing by the background tracer uptake in bone. We detected increased tracer uptake in 85% of the painful knees examined. We found that the painful knees exhibited increased tracer uptake compared to the pain-free knees of four subjects with unilateral pain (P = 0.0006). We also found a correlation between increasing tracer uptake and increasing pain intensity (r(2)  = 0.55; P = 0.0005). The implication of these results is that patellofemoral pain may be related to bone metabolic activity at the patellofemoral joint.

Combined single photon emission computerised tomography and conventional computerised tomography (SPECT/CT) in patellofemoral disorders: a clinical review

Patellofemoral disorders are common conditions seen in a knee clinic but can present a great diagnostic challenge to the orthopaedic surgeon. Combined single photon emission computerised tomography with conventional computer tomography (SPECT/CT) provides the clinician with precise anatomical and physiological information of the patellofemoral joint. We present a clinical review that highlights the value of SPECT/CT in patients with patellofemoral disorders, where other modalities such as radiographs, MRI, and conventional CT did not provide sufficient information. SPECT/CT has proven to be helpful for establishing the diagnosis and guidance for further treatment. SPECT/CT should be recognised as a valuable diagnostic tool in orthopaedic patients.

Hip strength and hip and knee kinematics during stair descent in females with and without patellofemoral pain syndrome

STUDY DESIGN

Cross-sectional.

OBJECTIVE

To determine if females presenting with patellofemoral pain syndrome (PFPS) from no discernable cause other than overuse demonstrate hip weakness and increased hip internal rotation, hip adduction, and knee valgus during stair descent.

BACKGROUND

Historically, PFPS has been viewed exclusively as a knee problem. Recent findings have indicated an association between hip weakness and PFPS. Researchers have hypothesized that patients who demonstrate hip weakness would exhibit increased hip internal rotation, hip adduction, and knee valgus during functional activities. To date, researchers have not simultaneously examined hip and knee strength and kinematics in subjects with PFPS to make this determination.

METHODS AND MEASURES

Eighteen females diagnosed with PFPS and 18 matched controls participated. Strength measures were taken for the hip external rotators and hip abductors. Hip and knee kinematics were collected as subjects completed a standardized stair-stepping task. Independent t tests were used to determine between-group differences in strength and kinematics during stair descent.

RESULTS

Subjects with PFPS generated 24% less hip external rotator (P = .002) and 26% less hip abductor (P =. 006) torque. No between-group differences (P > .05) were found for average hip and knee transverse and frontal plane angles during stair descent.

CONCLUSION

Subjects with PFPS had significant hip weakness but did not demonstrate altered hip and knee kinematics as previously theorized. Additional investigations are needed to better understand the association between hip weakness and PFPS etiology.

Decreased pulsatile blood flow in the patella in patellofemoral pain syndrome

BACKGROUND

Anterior knee pain without clinical and radiologic abnormalities has primarily been explained from a purely structural view. A recently proposed biologic and homeostatic explanation questions the malalignment theory. No objective measurement of the pathophysiology responsible for changes in local homeostasis has been presented.

HYPOTHESIS

Flexing the knee joint interferes with the perfusion of the patellar bone in patellofemoral pain syndrome.

STUDY DESIGN

Case control study; Level of evidence, 4.

METHODS

Pulsatile blood flow in the patella was measured continuously and noninvasively using photoplethysmography. Measurements were made with the patient in a resting position with knee flexion of 20 degrees and after passive knee flexion to 90 degrees. In total, 22 patients with patellofemoral pain syndrome were examined bilaterally, and 33 subjects with healthy knees served as controls.

RESULTS

The pulsatile blood flow in the patient group decreased after passive knee flexion from 20 degrees to 90 degrees (systematic change in position, or relative position [RP] = -0.32; 95% confidence interval for RP, -0.48 to -0.17), while the response in the control group showed no distinct pattern (RP = 0.17; 95% confidence interval for RP, -0.05 to 0.31). The difference between the groups was significant (P = .0002). The median change in patients was -26% (interquartile range, 37).

CONCLUSIONS

Pulsatile patellar blood flow in patellofemoral pain syndrome patients is markedly reduced when the knee is being flexed, which supports the previous notion of an ischemic mechanism involved in the pathogenesis of this pain syndrome.

Quantitative sensory testing of patients with long lasting Patellofemoral pain syndrome

BACKGROUND

Anterior knee pain, diagnosed as Patellofemoral Pain Syndrome (PFPS), is one of the most common musculoskeletal problems found in adolescents and young adults. There is no consensus in medical literature concerning the aetiology of the PFPS.

AIMS

To assess by means of Quantitative Sensory Testing (QST) whether patients suffering from long-lasting unilateral PFPS demonstrate somatosensory dysfunction related to afferent fibres from the local pain area.

METHODS

A descriptive non-experimental study with two independent samples, consisting of 25 men and women between 18 and 44 years of age with unilateral PFPS, and a comparable group of 23 healthy subjects. Somedic Thermotest apparatus was used to assess thresholds of thermal perception, and of heat and cold pain thresholds. Von Frey filaments were used to detect tactile sensitivity. Furthermore, quality and intensity of knee pain, symptoms and signs from a clinical neurological examination were recorded.

RESULTS

Decreased sensitivity to tactile stimulation, when tested with von Frey filaments, was demonstrated on both the painful and pain-free knee in subjects with PFPS, compared to the mean between the knees of the control group (p< or =0.001). The mean detection threshold for warmth was increased by 1.9 degrees C (p< or =0.01) in the painful knee, and 1.4 degrees C (p< or =0.01) in the non-painful knee in the PFPS group, compared to the mean of the healthy control group. The mean detection threshold for cold was increased by 1.6 degrees C (p< or =0.01) in the painful knee of the PFPS group, compared to the control group. These findings were supported by clinical sensory tests. No significant differences of mean thermal pain thresholds between the PFPS group and controls were found, and there were no significant differences in mean detection thresholds for warmth, cold or thermal pain thresholds between the painful and the non-painful knees in the PFPS group.

CONCLUSION

This study demonstrated an abnormal sensory function in the painful and non-painful knee in some individuals with long lasting unilateral Patellofemoral Pain Syndrome using Quantitative Sensory Testing supported by clinical neurological examinations. A dysfunction of the peripheral and/or the central nervous system may cause neuropathic pain in some subjects with PFPS.