Anterior knee pain

Radiomics-based diagnosis of patellar chondromalacia using sagittal T2-weighted images

OBJECTIVE

This study aimed to explore and evaluate a novel method for diagnosing patellar chondromalacia using radiomic features from patellar sagittal T2-weighted images (T2WI).

METHODS

The experimental data included sagittal T2WI images of the patella from 40 patients with patellar chondromalacia and 40 healthy volunteers. The training set comprised 30 cases of chondromalacia and 30 healthy volunteers, while the test set included 10 cases of each. A machine learning algorithm was used to train the classification model, which was then evaluated using standard performance metrics.

RESULTS

In the training set, the model achieved 24 true negatives (TN), 18 true positives (TP), 12 false negatives (FN), and six false positives (FP). Sensitivity, specificity, accuracy, and F1 score for the training set were 0.6, 0.8, 0.7, and 0.667, respectively. The model achieved six true negatives, eight true positives, two false negatives, and four false positives in the test set. Sensitivity, specificity, accuracy, and F1 score for the test set were 0.8, 0.6, 0.7, and 0.727, respectively.

CONCLUSION

The radiomic analysis method based on patellar sagittal fat-suppressed T2WI images demonstrates good diagnostic capability for patellar bone marrow edema.

Quadriceps strength, patellar tendon quality, relative load exposure, and knee symptoms in male athletes before the anterior cruciate ligament reconstruction

Introduction

Anterior cruciate ligament (ACL) injuries cause knee instability, knee pain, weight-bearing adjustments, and functional deficits but their association to patellar tendon quality is unknown. Our purpose was to investigate quadriceps strength, patellar tendon quality, relative load exposure, perceived knee stability, knee pain, extension angle, and time from ACL injury; in addition to examining their relative associations.

Methods

Injured and uninjured legs of 81 male athletes of different sports with a unilateral ACL injury (18-45 years) were examined. Participants reported location and intensity of knee pain and their perceived stability using a numerical rating scale (NRS 0-10). Strength was tested with an isokinetic device. Tendon quality was measured using ultrasound tissue characterization. Means ± standard deviation (SD) of perceived knee stability, knee extension angle, knee pain, isokinetic quadriceps strength in relation to body mass, proportion of echo-types (I-IV), tendon volume, and number of days from ACL injury to assessment are reported. Values of effect sizes (ES) and correlations (rs) were calculated.

Results

ACL injured leg demonstrated reduced reported knee stability (6.3 ± 2.5), decreased knee extension angle (-0.7 ± 3.1° vs. -2.7 ± 2.2°; ES = 0.7; P < 0.001), greater knee pain (NRS 3.1 ± 2.2 vs. 0.0 ± 0.1; ES = 2.0; P < 0.001), and 22% lower quadriceps strength (228.0 ± 65.0 vs. 291.2 ± 52.9 Nm/kg: ES = 1.2; P < 0.001) as compared to the uninjured leg. However, patellar tendons in both legs displayed similar quality. Quadriceps strength was associated with stability (rs = -0.54; P < 0.001), pain (rs = -0.47; P < 0.001), extension angle (rs = -0.39; P < 0.001), and relative load exposure (rs = -0.34; P < 0.004). Echo-types distribution was beneficially associated with time from ACL injury (rs range: -0.20/ -0.32; P < 0.05).

Discussion

ACL injured athletes displayed knee pain, extension deficit, and weaker quadriceps in the injured leg. While there were no differences in patellar tendon quality between legs, longer time from ACL injury showed better tendon quality.

Quantitative Assessment of Tendon Backscatter Anisotropy in B-Mode Ultrasound

To test the anisotropy of human tendons in conventional B-mode ultrasound, we prospectively performed ultrasound scans of 40 normal patella tendons and 24 patella tendons with chronic tendinopathy in adults. We scanned all tendons in longitudinal orientation (parallel to tendon fibers) using a linear array transducer (8.5 MHz) with beam steering at 0°, 5°, 10°, 15° and 20°. We used ImageJ histogram analysis to process B-mode images offline for assessing backscatter as a function of angle, known as backscatter anisotropy, between normal tendons and the subcutaneous tissues and between normal tendons and tendons with tendinopathy. We compared the results using the slopes of linear regression lines drawn through the angle-dependent data, and we concluded that the tissue anisotropy was significantly different if the 95% confidence intervals of the line slopes for different tissues did not overlap. We observed significant differences between normal tendons and both the adjacent subcutaneous tissues and tendons with tendinopathy. However, the difference in the regression slopes between tendons with tendinopathy and the adjacent subcutaneous soft tissues was not significant. It appears that changes in anisotropic backscatter could be used to detect tendon abnormalities and in assessing the significance of disease and the effectiveness of therapy.

Etiology and Prevention of Common Injuries in Golf

ABSTRACT

Golf is a popular sport played by individuals of varying age and skillsets. The golf swing is unique and complex, creating potential for various musculoskeletal injuries in both amateur and professional golfers. Understanding the basic biomechanics of the golf swing and its relation to injury etiology can assist the health care provider in recognizing and preventing musculoskeletal injuries secondary to golf. Most injuries occur in the upper limb and the lumbar spine. This review describes musculoskeletal pathologies seen in golfers with respect to anatomic area and golf swing biomechanics, while summarizing effective prevention strategies and swing modifications to address these potential injuries.

A case report of arthroscopic treatment of a retro-patellar GCTTS causing anterior knee pain

INTRODUCTION AND IMPORTANCE

Giant cell tumor of tendon sheath (GCTTS) is a common soft tissue tumor in hands and feet; however, it is rare in knee joints.

CASE PRESENTATION

We present a case of a 52-year-old female who had a retropatellar tendon giant cell tumor (GCT) in the right knee, causing vague anterior knee pain.

CLINICAL DISCUSSION

Anterior knee pain is a challenging complaint in orthopedics due to the multiple causative reasons, the combination of several complex etiologies, and the lack of clear guidelines for an effective treatment.

CONCLUSION

This case report aims to shed light on unlikely pathologies in complex cases. GCTTS is a rare lesion to affect the retropatellar region. However, we must keep it in mind when dealing with challenging anterior vague knee pain complaints. A comprehensive examination is essential; surgical experience and extended follow-up are mandatory for avoiding complications.

Nearly 40% of adolescent athletes report anterior knee pain regardless of maturation status, age, sex or sport played

OBJECTIVE

To report point prevalence of anterior knee pain (AKP) in adolescent athletes by (1) maturation status, (2) chronological age, (3) sex, and (4) primary sport.

DESIGN

Cross-sectional.

METHODS

Male and female participants aged 11-15 years were recruited from specialised sports programs for basketball, volleyball, Australian Rules Football and tennis. Standing height, sitting height, and body mass were measured and used to calculate maturity status. Past injury history, self-reported physical activity, and Victorian Institute of Sport Assessment Questionnaire Patellar Tendon (VISA-P) questionnaires were completed. Anterior knee pain was defined as any pain experienced on the anterior surface of the knee and recorded using a visual analogue scale (VAS). A single leg decline squat (SLDS) was performed for provocation of AKP.

RESULTS

Two hundred and seventeen male and female adolescent athletes participated in this study. Twenty participants were excluded from data analysis. Point prevalence of AKP was 39% (N = 76). Average self-reported physical activity/week was 7.9 ± 4.1 h of their specialised sport and 2.0 ± 2.0 h of other physical activity/week. Maturation status, chronological age, sex nor primary sporting program was statistically significant in explaining the presence or absence of AKP.

CONCLUSION

Due to the right-skewed maturation sample, the authors cannot state conclusively that maturation status was not associated with AKP. Nearly 40% of this cohort reported AKP during a pain provocation test. The presence of AKP was not explained by maturation status, age, sex or primary sport program. Given the chronic nature of AKP and future morbidity reported, this high prevalence provides rationale for intervention or prevention studies targeting younger athletes.

Cryoablation of the Infrapatellar Branch of the Saphenous Nerve Identified by Non-Invasive Peripheral Nerve Stimulator for the Treatment of Non-Surgical Anterior Knee Pain: A Case Series and Review of the Literature

Chronic, non-surgical, non-specific anterior knee pain is a common source of functionally limiting chronic ailment, especially in a young athletic and active-duty military population. The infrapatellar branch of the saphenous is becoming a common therapeutic target for the diagnosis and treatment of anterior knee pain. It is a nerve commonly injured during knee surgeries and trauma, resulting in neuroma formation and chronic neuropathic pain states, and it can also transmit nociceptive input from patients with non-surgical anterior knee pain of multiple etiologies. Several methods have been employed to treat this condition. After the diagnosis of infrapatellar saphenous neuralgia, the nerve is safely ablated using radiofrequency ablation, neurolytic solutions, and, most recently, cryoablation using the handheld iovera® cryoablation system (Myoscience, Inc. Fremont, CA). Cryoablation is an attractive technique because it is minimally invasive, not permanent, and well tolerated by the patient with only local anesthesia. We have previously described a technique using a non-invasive peripheral nerve stimulator to identify and treat the exact location of the nerve more precisely, thereby optimizing treatment success and procedural simplicity. This case series illustrates our initial use and success with this technique. Further follow-up and randomized sham-controlled trials are also planned.

The association between patellar tendon stiffness measured with shear-wave elastography and patellar tendinopathy-a case-control study

OBJECTIVES

(1) To determine the association between patellar tendon stiffness and the presence of patellar tendinopathy (PT). (2) To evaluate the reliability of shear-wave elastography (SWE).

METHODS

Participants were consecutively enrolled between January 2017 and June 2019. PT was diagnosed clinically and confirmed by either grayscale US or power Doppler US, or both. Controls had no history of anterior knee pain and no clinical signs of PT. Patellar tendon stiffness (kilopascal, kPa) was assessed using SWE. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Reliability analyses included coefficients-of-variation (CV), coefficients-of-repeatability (CR), intraclass correlation coefficient (ICC) for intraobserver and interobserver reliability, and Bland-Altman analysis.

RESULTS

In total, 76 participants with PT (58 men, mean age 24.4 ± 3.8 years) and 35 asymptomatic controls (16 men, mean age 21.5 ± 3.8 years) were included. Univariate analyses (OR 1.094, 95% CI 1.061-1.128, p < .001) and adjusted multivariate analyses (OR 1.294, 95% CI 1.044-1.605, p = .018) showed that athletes with PT had significantly increased patellar tendon stiffness. ICC for intraobserver reliability was 0.95 (95% CI 0.92-0.97), CR (CV) 12 kPa (10%) and 0.79 (95% CI 0.65-0.88), CR (CV) 18 kPa (21%) for interobserver reliability. Mean differences from Bland-Altman analysis were 5.6 kPa (95% CI 3.1-8.1, p < .001) for intraobserver reliability and 4.6 kPa (95% CI 1.9-7.2, p < .001) for interobserver reliability.

CONCLUSIONS

PT is associated with significantly higher patellar tendon stiffness. SWE measurements demonstrate excellent intraobserver reliability and good interobserver reliability. Therefore, SWE is a promising tool to implement in longitudinal studies and future studies should evaluate its prognostic value and utility as a monitoring tool in athletes with PT.

KEY POINTS

• Patellar tendon stiffness measured with shear-wave elastography (SWE) is higher in athletes with patellar tendinopathy than in healthy controls, also after adjusting for potential confounders. • Excellent intraobserver reliability and good interobserver reliability were found for the quantitative assessment of patellar tendon stiffness using SWE.

Magnetic resonance imaging of impingement and friction syndromes around the knee

The knee is a complex joint with its function dependent on a combination of osseous and soft tissue structures. Alteration in the relationship of these tissues, due to either acute or chronic repetitive injury with possible underlying congenital predisposing factors, can result in impingement between the structures resulting in pain, particularly on activity. The purpose of this article is to provide a comprehensive review of the MRI features of various impingement syndromes around the knee.

A study of the possible effect of abnormal patella height on meniscal tears

Objective

Patellar height is key to knee biomechanics. Variations (alta/baja) have been associated with instability/dislocations, ACL ruptures etch. The effect of abnormal patella height and meniscal lesions is not clear yet; this is a first investigation of this relation.

Methods

100 patients with meniscal tears were X-Rayed to determine patellar height using the Insall-Salvati ratio and the Caton-Deschamps Index.

Results

20% had abnormal patellar height according to the Insall-Salvati ratio and 9% based on the Caton-Deschamps index.

Conclusion

This indicates that patella height could be a parameter in the occurrence of meniscal injuries worth investigating in larger populations; yet the mechanism remains unclear.

Relation of the chondromalatia patellae to proximal tibial anatomical parameters, assessed with MRI

Background Magnetic resonance imaging (MRI) is a non-invasive highly sensitive tool for diagnosing chondromalacia patellae in the early stages. Many studies have evaluated patellar and trochlear morphology with different radiologic indices. We aimed to assess the discriminative power of tibial, patellar, and femoral indices in MRI for chondromalacia patellae. Patients and methods 100 cases of chondromalacia, as well as 100 age-matched controls among the patients who underwent knee MRI between February 2017 and March 2019, were included. The standard protocol of knee MRI was applied and the diagnosis of chondromalacia was made on MRI findings. Chondromalacia subjects were also classified as grade 1 to 4 according to the Modified Outerbridge's MRI grading system. We measured 25 MRI parameters in the knee and adjacent structures to determine the relation between chondromalacia patellae and anatomical MRI parameters. Results Tibial slope, trochlear depth, lateral trochlear inclination, and lateral patellar tilt angle had significant correlation with chondromalacia. Any increase in lateral trochlear inclination and lateral patellar tilt angle could increase the probability of the disease (Odds ratio [OR] 1.15, 1.13; 95% CI: 1.03-1.30; 1.02-1.26, respectively), while any increase in medial tibial slope and trochlear depth could decrease the probability of chondromalacia (OR 0.85, 0.06; 95% CI: 0.73-0.98, 0.02-0.17, respectively). We also designed a model for the severity of disease by using the patellar height index (relative odds ratio: 75.9). Conclusions The result of this study showed the novelty role of tibial anatomy in developing chondromalacia and its mechanism. We also concluded that patellar height might be an important factor in defining disease severity.

Knee Joint and Quadriceps Dysfunction in Individuals With Anterior Knee Pain, Anterior Cruciate Ligament Reconstruction, and Meniscus Surgery: A Cross-Sectional Study

CONTEXT

While arthrogenous muscle inhibition associated with knee injuries is evident, the relative magnitude of functional deficiency related to each individual knee pathology is unclear.

OBJECTIVE

To compare the knee joint and quadriceps dysfunction among patients with anterior knee pain (AKP) without surgical history and those with surgical history (anterior cruciate ligament reconstruction [ACLR]; meniscus surgery) without current AKP, with matched healthy controls.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PARTICIPANTS

A total of 66 patients with knee pathologies and 30 controls.

MAIN OUTCOME MEASURES

Pain perception and lower-extremity functional outcomes were assessed. Knee joint function was measured by replication tests. Quadriceps function was measured by strength, voluntary activation, and torque-generating capacity.

RESULTS

Patients with AKP reported greater pain perception compared with the other knee conditions (4.3 vs 0.1 of 10 in Numeric Pain Rating Scale, P < .0001). Compared with the controls: (1) patients with AKP showed a greater error on knee-flexion replications at 75° (2.9° vs 5.4°, P = .002), (2) patients with AKP and ACLR showed less quadriceps strength (AKP: 3.3 vs 2.6 N·m/kg, P = .002; ACLR: 3.3 vs 2.7 N·m/kg, P = .02) and voluntary activation (AKP: 0.982 vs 0.928, P < .0001; ACLR: 0.982 vs 0.946, P = .003), and (3) all knee pathologies reported lower scores on functional outcomes (79 vs 65 of 80 points in Lower-Extremity Functional Scale, P < .0001) and showed less quadriceps torque-generating capacity (10.7 vs 7.8 N·m/s/kg, P < .0001). Among the knee pathologies, patients with AKP showed less quadriceps voluntary activation compared with the patients with meniscus surgery (0.928 vs 0.964, P = .03).

CONCLUSION

As patients with AKP had an additional impairment in knee joint flexion replications and reported a less score in functional outcomes, knee pain may produce a greater impact on functional deficiency.

Evaluation of the Knees of Asymptomatic Kangoo Jumpers with MR Imaging

Purpose:

The aim of this study is to determine the prevalence of pathologic findings in asymptomatic knees of Kangoo Jumpers by using a 3T MRI and to compare them with age and sex-matched controls who do not regularly participate in any impact sports.

Methods:

Both knees of 18 Kangoo Jumpers were examined by 3T MRIs in a total of 36 MRI scans. The control group was comprised of 20 volunteers from the same age group and with similar weights who did not participate in any competitive sports, in a total of 40 MRI scans. Two orthopedists and one radiologist independently assessed all images for the presence or absence of any abnormalities.

Results:

In 32 (88.9%) of the 36 Kangoo Jumpers’ knees, one or more abnormalities were observed. The most prevalent abnormality was bone marrow edema, which was detected in 32 knees (88.9%). The other significant findings were quadriceps tendinopathy (80.6%), patellar tendinopathy (63.9%), gastrocnemius tendinopathy (63.9%), infrapatellar fat pad edema (75%), suprapatellar fat pad edema (63.9%), meniscal signal change (72.2%) and cartilage damage in the patellofemoral joint (72.2%). There were no statistically significant differences in terms of joint effusion (8.3%), ganglion cysts (8.3%) or tibiofemoral joint cartilage injury (0%).

Conclusion:

This study reveals many types of knee MRI findings of asymptomatic Kangoo Jumpers compared to the control group. These MRI findings may be associated with acute knee injuries or chronic joint problems such as osteoarthritis, which may develop in long-term follow-up studies.

Magnetic resonance imaging of the quadriceps fat pad oedema pattern in relation to patellofemoral joint pathologies

Purpose

Quadriceps fat pad is located posterior to the quadriceps tendon. Increased signal intensity of this fat pad is seen on routine knee magnetic resonance imaging (MRI) examinations, but the exact mechanism and related pathologies are not clear. In this study we aimed to evaluate the relationship between MRI signal intensity and morphological features of quadriceps fat pad, as well as various pathologies of the patellofemoral joint.

Material and methods

Sixty-one knees with quadriceps fat pad oedema out of 457 knee MRI examinations were included. Quadriceps fat pad signal intensity, dimensions, posterior indentation, and various parameters related to patellofemoral joint such as trochlear facet asymmetry, trochlear depth and sulcus angle, and the Insall-Salvati ratio were evaluated.

Results

There was no statistically significant correlation between quadriceps fat pad oedema intensity and its dimensions, but it was significant when compared to posterior indentation. There was no correlation between fat pad oedema and each of the pathologies. However, there was a significant correlation between the presence of fat pad oedema and the presence of at least one of the pathologies related to patellofemoral joint.

Conclusions

Quadriceps fat pad oedema detected in MRI examinations should warn the radiologist against the presence of various pathologies related to the patellofemoral joint.

Ultrasound evaluation of infrapatellar fat pad impingement: An exploratory prospective study

BACKGROUND

We sought to determine whether there are ultrasound parameters that differ between knees with symptomatic fat pad synovial impingement and asymptomatic knees.

METHODS

A prospective study was performed in patients with clinical signs and symptoms of fat pad synovial impingement and asymptomatic controls. Eleven symptomatic knees and 10 asymptomatic controls were evaluated. Ultrasound imaging was performed before and after exercise. Evaluated parameters included largest fat lobule compressibility, subjective assessment of vascularity, largest vessel diameter, and subjective assessment of dynamic fat pad motion during flexion and extension. Receiver operating characteristic (ROC) curve analysis was used to assess whether changes in these parameters were different between symptomatic and asymptomatic knees.

RESULTS

Change in the largest vessel diameter was greater and trended toward dilation in asymptomatic knees compared to symptomatic knees (mean: 0.83 vs. -0.02; P<0.001). No significant differences were observed between symptomatic and asymptomatic knees with respect to pre-exercise versus post-exercise states in subjective assessment of vascularity (P=0.131), fat pad motion (P=0.115), or percent change of the largest fat lobule (P=0.241). However, overall compressibility of the fat pad lobule was significantly diminished in the pre-exercise state in symptomatic knees compared to asymptomatic controls.

CONCLUSIONS

This study demonstrated a statistically significant change in the largest vessel diameter from pre- to post-exercise states between symptomatic and asymptomatic knees, as well as abnormal pre-exercise fat lobule compressibility in symptomatic knees. These findings show promise that with further research, ultrasound could have clinical utility in diagnosing infrapatellar fat pad impingement.

The relation between chondromalacia patella and meniscal tear and the sulcus angle/ trochlear depth ratio as a powerful predictor

PURPOSE

To investigate the relation between chondromalacia patella and the sulcus angle/trochlear depth ratio as a marker of trochlear morphology. In addition, we also planned to show the relationship between meniscus damage, subcutaneous adipose tissue thickness as a marker of obesity, patellar tilt angle and chondromalacia patella.

METHODS

Patients with trauma, rheumatologic disease, a history of knee surgery and patellar variations such as patella alba and patella baja were excluded. Magnetic resonance images of the knees of 200 patients were evaluated. Trochlear morphology from standardized levels, patellar tilt angle, lateral/medial facet ratio, subcutaneous adipose tissue thickness from 3 locations and meniscus injury were assessed by two specialist radiologists.

RESULTS

Retropatellar cartilage was normal in 108 patients (54%) at radiological evaluation, while chondromalacia patella was determined in 92 (46%) cases. Trochlear sulcus angle and prepatellar subcutaneous adipose tissue thickness were significantly high in patients with chondromalacia patella, while trochlear depth and lateral patellar tilt angle were low. The trochlear sulcus angle/trochlear depth ratio was also high in chondromalacia patella and was identified as an independent risk factor at regression analysis. Additionally, medial meniscal tear was observed in 35 patients (38%) in the chondromalacia patella group and in 27 patients (25%) in the normal group, the difference being statistically significant (P = 0.033).

CONCLUSIONS

An increased trochlear sulcus angle/trochlear depth ratio is a significant predictor of chondromalacia patella. Medial meniscus injury is more prevalent in patients with chondromalacia patella in association with impairment in knee biomechanics and the degenerative process.

Stump Entrapment of the Torn Anterior Cruciate Ligament

We present a case of anterior cruciate ligament stump entrapment in a 24-year-old gentleman who traumatically injured his knee. The anterior stump became entrapped in the intercondylar notch and after a process of inflammation and fibrosis, produced a mass similar to the more familiar cyclops lesion that may complicate anterior cruciate ligament reconstruction.

Abnormal Patella Height Based on Insall-Salvati Ratio and its Correlation with Patellar Cartilage Lesions: An Extremity-Dedicated Low-Field Magnetic Resonance Imaging Analysis of 1703 Chinese Cases

Background and aims:

Diagnostic performance of patellar position for patellar cartilage lesions remains unclear. The aim of this study was to assess the abnormal patella height and its correlation with chondral lesions of the patellofemoral joint in China.

Material and methods:

A total of 1703 consecutive patients who performed knee joint examination using an extremity-dedicated low-field magnetic resonance imaging were enrolled in this study. Patellar cartilage lesions were diagnosed based on the result of magnetic resonance imaging and clinical data. Patella height was defined as the ratio of patellar tendon length to patellar length according to Insall-Salvati index. Patella alta and infera were defined as tendon length/patellar length >1.2 and <0.8, respectively.

Results:

The total prevalence of patellar cartilage lesions was 38.0%. The prevalence in females was significantly higher than that in males (46.4% vs 28.8%, p < 0.001). Age notably increased the incidence of patellar cartilage lesions ( p < 0.001). Logistic regression analysis showed that tendon length/patellar length ratio was significantly correlated with patellar cartilage lesions (odds ratio = 6.380, p < 0.001). Furthermore, patients with cartilage lesions showed significantly higher rates of patella alta and infera ( p < 0.001). In addition, receiver operating characteristic curve analysis demonstrated that abnormal patella height had statistical significance in diagnosing cartilage lesions ( p < 0.001). However, the area under the curve (0.596; 95% confidence interval: 0.568–0.624) and sensitivity (47.0%) were relatively low, while the specificity was 72.2%.

Conclusions:

Patients with patellar cartilage lesions have an increased tendon length/patellar length ratio. The abnormal patella height is significantly correlated with chondral lesions and can be used as a potential diagnostic marker.

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.

Functional Knee Extension Test (FKET): Inter-rater palpatory agreement and visual analysis during a non-weight bearing functional assessment of the knee

OBJECTIVE

The purpose of this study was to evaluate the inter-rater reliability of the Functional Knee Extension Test (FKET), a non-weight bearing functional assessment of the knee that is utilized within clinical practice.

METHODS

The design was a single-session, test-retest reliability study. Active knee extension was assessed and documented by each examiner for each of the visual, palpatory and vastus medialis obliqus (VMO) components of the FKET on fifty-seven healthcare professionals.

RESULTS

The Kappa (κ) statistic for the inter-rater reliability for the visual, palpatory and VMO variables of the FKET were slight-to-fair (0.13-0.26), fair-to-moderate (0.39-0.50), and moderate-to-almost perfect (0.57-0.93) reliability, respectively. The p-values for all variables, besides 'Visual RIGHT: TibTubExt' and 'Visual LEFT: TibTubExt' indicated statistically significant evidence of agreement above random guessing. Estimates for κ on the 'VMO Quantity: No contact' and 'VMO Timing: Start then stop' variables could not be calculated as ratings only existed across one row of the crosstabulation.

CONCLUSION

This study demonstrated that the palpatory and VMO components of the FKET have sufficient reliability to justify utilization within clinical practice. Future research is needed to determine whether the implementation of a functional knee assessment protocol, including the FKET could enhance levels of reliability in clinical decision-making of knee function.

Common overuse injuries in the young athlete

Pediatric overuse injury is a common complaint presenting to pediatricians. Overuse injury can affect the soft tissues or bone, and results from an imbalance between training and load to the tissues and recovery time. In the skeletally immature athlete, physeal and apophyseal tissue is particularly vulnerable to overuse resulting in different patterns of injury compared to adults. Awareness of age-dependent patterns of overuse is necessary for proper recognition, treatment, and prevention of injury. This article reviews the most common pediatric overuse injuries with emphasis on risk factors, diagnosis, and treatment. Guidelines for prevention are included, as this is the key component for successful management of overuse injury in pediatric athletes.

Prevalence and clinical significance of chondromalacia isolated to the anterior margin of the lateral femoral condyle as a component of patellofemoral disease: observations at MR imaging

OBJECTIVE

To determine the prevalence of chondromalacia isolated to the anterior margin of the lateral femoral condyle as a component of patellofemoral disease in patients with anterior knee pain and to correlate it with patient demographics, patellar shape, and patellofemoral alignment.

MATERIALS AND METHODS

Retrospective study over a 1-year period reviewing the MR knee examinations of all patients who were referred for assessment of anterior knee pain. Only patients with isolated lateral patellofemoral disease were included. Age, gender, distribution of lateral patellofemoral chondromalacia, and grade of cartilaginous defects were documented for each patient. Correlation between the distribution of lateral patellofemoral chondromalacia and patient demographics, patellar shape, and indices of patellar alignment (femoral sulcus angle and modified Q angle) was then ascertained.

RESULTS

There were 50 patients (22 males, 28 females) with anterior knee pain and isolated patellofemoral disease. The majority of the patients (78 %) had co-existent disease with grade 1 chondromalacia. No significant correlation was found between patients with chondromalacia isolated to the anterior margin of the lateral femoral condyle and age, gender, patellar shape, or modified Q angle (p > 0.05). However, patients with chondromalacia isolated to the anterior margin of the lateral femoral condyle had a shallower femoral sulcus angle (mean 141.8°) compared to the patients with lateral patellar facet disease (mean 133.8°) (p = 0.002).

CONCLUSIONS

A small percentage of patients with anterior knee pain have chondromalacia isolated to the anterior margin of the lateral femoral condyle. This was associated with a shallower femoral sulcus angle.

Suprapatellar fat-pad mass effect: MRI findings and correlation with anterior knee pain

OBJECTIVE

The purpose of this study was to evaluate the MRI characteristics of the suprapatellar fat-pad, determine the prevalence and pattern of suprapatellar fat-pad edema, and correlate the findings with the presence of anterior knee pain, patellofemoral malalignment, and patellofemoral joint osteoarthritis.

MATERIALS AND METHODS

We retrospectively reviewed 879 consecutive knee MRI examinations of 843 patients for the presence of a suprapatellar fat-pad mass effect on the suprapatellar joint recess. The relative signal intensity and the maximum anteroposterior, craniocaudal, and oblique diameters of the suprapatellar fat-pad on sagittal fat-suppressed intermediate-weighted turbo spin-echo images were measured. Findings of anterior knee pain, patellofemoral malalignment, and patellofemoral joint osteoarthritis were also recorded. The Fisher exact, Mann-Whitney, and independent samples Student t tests and Spearman rank correlation coefficient were used for statistical analysis.

RESULTS

The prevalence of suprapatellar fat-pad mass effect on the suprapatellar joint recess in our study population was 13.8%. The relative signal intensity (p < 0.0001) and maximum anteroposterior (p < 0.0001), craniocaudal (p = 0.0017), and oblique (p < 0.0001) diameters of the pad were significantly greater in patients with a mass effect. Significant correlation was found between the relative signal intensity and the maximum anteroposterior (ρ = 0.0986, p = 0.0053), craniocaudal (ρ = 0.0968, p = 0.0062), and oblique (ρ = 0.123, p = 0.0005) diameters. Mass effect was not significantly associated with anterior knee pain, patellofemoral malalignment, or patellofemoral joint osteoarthritis. Six patients with suprapatellar fat-pad edema had anterior knee pain.

CONCLUSION

Suprapatellar fat-pad edema with a mass effect on the suprapatellar joint recess is a common finding at MRI examinations of the knee that is rarely associated with anterior knee pain.

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.

Suprapatellar fat pad inflammation in step aerobics athletes: MR imaging evaluation of two cases

Step aerobics is one of the most popular exercises with established benefits to cardiovascular status. This activity is associated with injuries which include patellar or talar chondral lesions, quadriceps tendinopathy, Achilles tendinopathy or tear, shin splints and muscle soreness. The purpose of this case report is to present two step aerobics athletes, suffering from anterior knee pain. We observed that their knee MR examination disclosed only suprapatellar fat pad edema. No other findings were noticed. In addition, we discuss the possible pathogenetic mechanism of this entity which has not been previously reported in the literature.

Sensitivity of MRI for articular cartilage lesions of the patellae

BACKGROUND AND AIMS

Reliable diagnosis of articular cartilage lesions of the patellae is often based on arthroscopy. However, unnecessary arthroscopies should be avoided. The aim of this study was to assess the sensitivity and applicability of MRI to diagnosing articular cartilage lesions of the patellae.

MATERIALS AND METHODS

We identified 74 consecutive males (mean age 21 years, range 18-28) from the medical records of our institute with the sole diagnosis of articular cartilage lesions of the patellae based on arthroscopy. Magnetic resonance imaging was performed with 1.0 Tesla scanner a mean of 4 weeks before arthroscopy. Sensitivity of symptoms, and MRI for the diagnosis was calculated.

RESULTS

Based on arthroscopy, 20 (27%) cases of cartilage lesions of the patellae were grade-I, 32 (43%) were grade-II, and 22 (30%) were grade-III. MRI revealed cartilage lesions of the patellae in 49 knees (66%), indicating that the sensitivity of MRI was 66% (95% CI: 53%-74%). MRI sensitivity increased with the severity of chondral lesions: all grade III to IV lesions were detected (sensitivity 100%, 95% CI: 85%-100%) by MRI. Grade of articular cartilage lesions of the patellae based on arthroscopy was not associated with clinical symptoms (p=0.61).

CONCLUSIONS

The sensitivity of 1.0 Tesla MRI for detecting grade-I lesions was low and could not be used to confirm the diagnosis of articular cartilage lesions of the patellae. For the detection of more severe grade-II to III lesions, the MRI sensitivity was markedly higher. MRI may thus be considered an accurate diagnostic tool for identifying more severe cases of articular cartilage lesions of the patellae.

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.

Evaluation and treatment of disorders of the infrapatellar fat pad

The infrapatellar fat pad (IFP), also known as Hoffa's fat pad, is an intracapsular, extrasynovial structure that fills the anterior knee compartment, and is richly vascularized and innervated. Its degree of innervation, the proportion of substance-P-containing fibres and close relationship to its posterior synovial lining implicates IFP pathologies as a source of infrapatellar knee pain. Though the precise function of the IFP is unknown, studies have shown that it may play a role in the biomechanics of the knee or act as a store for reparative cells after injury. Inflammation and fibrosis within the IFP, caused by trauma and/or surgery can lead to a variety of arthrofibrotic lesions including Hoffa's disease, anterior interval scarring and infrapatellar contracture syndrome. Lesions or mass-like abnormalities rarely occur within the IFP, but their classification can be narrowed down by radiographical appearance. Clinically, patients with IFP pathology present with burning or aching infrapatellar anterior knee pain that can often be reproduced on physical exam with manoeuvres designed to produce impingement. Sagittal MRI is the most common imaging technique used to assess IFP pathology including fibrosis, inflammation, oedema, and mass-like lesions. IFP pathology is often successfully managed with physical therapy. Passive taping is used to unload or shorten an inflamed IFP, and closed chain quadriceps exercises can improve lower limb control and patellar congruence. Training of the gluteus medius and stretching the anterior hip may help to decrease internal rotation of the hip and valgus force at the knee. Gait training and avoiding hyperextension can also be used for long-term management. Injections within the IFP of local anaesthetic plus corticosteroids and IFP ablation with ultrasound guided alcohol injections have been successfully explored as treatments for IFP pain. IFP pathology refractory to physical therapy can be approached through a variety of operative treatments. Arthroscopic partial resection for IFP impingement and Hoffa's disease has showed favourable results; however, total excision of the IFP performed concomitantly with total knee arthroplasty (TKA) resulted in worse results when compared with TKA alone. Arthroscopic debridement of IFP fibrosis has been successfully used to treat extension block following anterior cruciate ligament reconstruction, and arthroscopic anterior interval release has been an effective treatment for pain associated with anterior interval scarring. Arthroscopic resection of infrapatellar plicae and denervation of the inferior pole of the patella have also been shown to be effective treatments for refractory infrapatellar pain.

Magnetic resonance imaging in patellar lateral femoral friction syndrome (PLFFS): prospective case-control study

OBJECTIVES

To describe morphologic abnormalities and signs of patellar lateral femoral friction syndrome (PLFFS) detected by magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Prospective study of 56 knees (21 patients and 30 controls) studied by 3Tesla MRI. Comparative analysis of clinical data, quantitative and qualitative imaging criteria in a population of patients with anterior knee pain associated with an abnormal MRI signal along the lateral alar folds of the infrapatellar fat pad, a characteristic sign of PLFFS, and a control population with no anterior knee pain or abnormal signal from the infrapatellar fat pad.

RESULTS

Patients with PLFFS have anterior and/or lateral knee pain. Their knee has anatomical predispositions for instability, primarily with patella alta (P<0.0001), patellar tilt more than 13.5° (P<0.0001), a patellar nose length less than 9 mm (P=0.0037), a patellar nose ratio less than 0.25 (P<0.0001), a TT-TG distance more than 10 mm (P<0.0001), and a trochlear prominence more than 4 mm (P=0.0056). In 35% of patients, patellar chondropathy is visible, and 48% of patients have patellar or trochlear subchondral abnormalities.

CONCLUSION

Anterior, lateral, and medial knee pain may be related to PLFFS. Anatomical predispositions contributing to instability are found in these patients. There may be associated chondropathies and osteochondropathies.

Articularis genus: an anatomic and MRI study in cadavers

BACKGROUND

The articularis genus muscle is closely associated with the anterior aspect of the knee joint and may act to elevate or retract the suprapatellar bursa. Its form and function are poorly understood. The purpose of this study was to define the morphology of the articularis genus and its relationship to the suprapatellar bursa.

METHODS

The articularis genus muscle was investigated in twenty-two human lower limbs obtained from eleven donors (six men and five women; mean age at death, eighty-three years). Eighteen of these limbs underwent magnetic resonance imaging (MRI) followed by dissection. The number, length, physiological cross-sectional area, attachment sites, and orientation of individual fascicles, muscle bundles, and whole muscles were recorded. The remaining four limbs underwent immunohistochemical analysis to determine muscle fiber types.

RESULTS

The articularis genus comprised multiple layered muscle bundles originating from the anterior, anterolateral, and/or anteromedial surfaces of the distal third of the femur. Distal attachment sites included the proximal and/or posterior wall of the suprapatellar bursa, the deep surface of the distal tendon of the vastus intermedius, and the medial and lateral aspects of the knee joint capsule. On dissection, the muscle was observed to consist of a mean of seven muscle bundles (range, four to ten), but only a mean of four bundles were observed on MRI scans (p &lt; 0.0001). The mean cross-sectional area of the articularis genus (and standard deviation) was 1.5 ± 0.7 cm2, and its mean fascicular length and bundle physiological cross-sectional area were 5.9 ± 1.0 cm and 0.2 ± 0.1 cm2, respectively. The articularis genus displayed a mixed fiber type, with the proportion of type-I fibers varying among specimens (range, 39.9% to 76.4%).

CONCLUSIONS

These findings highlight the complex and variable anatomy of the articularis genus, particularly with respect to the number of bundles and the distal attachment sites. Distinguishing the superficial bundles of the articularis genus from the vastus intermedius on MRI can be difficult.

CLINICAL RELEVANCE

Given its relationship to the anterior aspect of the knee joint and its association with the suprapatellar bursa, the articularis genus may be a neglected cause of undifferentiated anterior knee pain.

Patellar maltracking correlates with vastus medialis activation delay in patellofemoral pain patients

BACKGROUND

Delayed onset of vastus medialis (VM) activity compared with vastus lateralis activity is a reported cause for patellofemoral pain. The delayed onset of VM activity in patellofemoral pain patients likely causes an imbalance in muscle forces and lateral maltracking of the patella; however, evidence relating VM activation delay to patellar maltracking is sparse. The aim of this study was to investigate the relationship between VM activation delay and patellar maltracking measures in pain-free controls and patellofemoral pain patients.

HYPOTHESIS

Patellar tilt and bisect offset, measures of patellar tracking, correlate with VM activation delay in patellofemoral pain patients classified as maltrackers.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

Vasti muscle activations were recorded in pain-free (n = 15) and patellofemoral pain (n = 40) participants during walking and jogging. All participants were scanned in an open-configuration magnetic resonance scanner in an upright weightbearing position to acquire the position of the patella with respect to the femur. Patellar tilt and bisect offset were measured, and patellofemoral pain participants were classified into normal tracking and maltracking groups.

RESULTS

Correlations between VM activation delay and patellar maltracking measures were statistically significant in only the patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset (R(2) = .89, P < .001, with patellar tilt during walking; R(2) = .75, P = .012, with bisect offset during jogging). There were no differences between the means of activation delays in pain-free and all patellofemoral pain participants during walking (P = .516) or jogging (P = .731).

CONCLUSION

There was a relationship between VM activation delay and patellar maltracking in the subgroup of patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset.

CLINICAL RELEVANCE

A clinical intervention such as VM retraining may be effective in only a subset of patellofemoral pain participants-namely, those with excessive tilt and excessive bisect offset measures. The results highlight the importance of appropriate classification of patellofemoral pain patients before selection of a clinical intervention.

MRI of the knee joint in asymptomatic adolescent soccer players: a controlled study

OBJECTIVE

The knee is the joint that is most frequently injured in boys 12-15 years old who practice soccer, and MRI is an accurate method of diagnosing sports-related injuries. The objective of this cross-sectional case-control study was to evaluate the knees of asymptomatic adolescent soccer players using open MRI.

SUBJECTS AND METHODS

We evaluated 56 knees of 28 asymptomatic male adolescents 14-15 years old. Participants were divided into two groups and paired by age and weight: soccer players (28 knees) and control subjects (28 knees). All the examinations were performed using a 0.35-T open-field MRI unit and were evaluated by two experienced radiologists blinded to study groups. Bone marrow signal, articular cartilage, meniscus, and fat pad abnormalities and the amount of fluid were assessed.

RESULTS

In the group of soccer players, 18 knees (64.3%) had one or more MRI abnormalities, whereas in the control group nine knees (32.1%) had at least one MRI abnormality (p = 0.03). The prevalence of bone marrow edema was much greater in the group of soccer players (14 knees, 50%), whereas the same abnormality was found in only one knee (3.6%) in the control group (p = 0.0001). Other abnormalities that were not statistically significant with regard to study group were also found in the two groups: infrapatellar fat pad edema, popliteal cysts, and ganglion cysts.

CONCLUSION

Bone marrow edema is a prevalent abnormal finding on MRI scans of knees of asymptomatic adolescent soccer players. MRI findings should be interpreted cautiously and in close correlation with clinical findings.