Imaging of patellofemoral disorders

doi:10.1016/j.crad.2004.01.004

Clinical Radiology

Volume 59, Issue 7, July 2004, Pages 543-557

https://doi.org/10.1016/j.crad.2004.01.004 Get rights and content

Abstract

Anterior knee pain is a common symptom, which may have a large variety of causes including patellofemoral pathologies. Patellofemoral maltracking refers to dynamic abnormality of patellofemoral alignment and has been measured using plain film, computed tomography (CT) and magnetic resonance imaging (MRI) using static and kinematic techniques. Patellar dislocation is usually transient, but specific conventional radiographic and MRI features may provide evidence of prior acute or chronic dislocation. In addition, chondromalacia patellae, osteochondritis dissecans, patellofemoral osteoarthritis, excessive lateral pressure syndrome, and bipartite patella have all been implicated in causing patellofemoral pain. The imaging and clinical features of these processes are reviewed, highlighting the specific diagnostic features of each condition.

Introduction

Patellofemoral disorders commonly cause anterior knee pain and giving way. Anatomical features associated with these disorders, and features of joint degeneration or prior trauma can be identified clinically and radiologically. However, the link between anatomical or pathological findings and symptoms is variable, and many surgical procedures used for patellofemoral disorders have variable results, especially at long-term follow-up.¹ This may be in part because patellofemoral relationships are usually measured in the supine resting knee, but failure occurs in the loaded, functioning joint. Methods for imaging the joint in both resting and functional states will be reviewed.

Section snippets

Anatomical and biomechanical considerations

The posterior surface of the patella articulates with the trochlear groove along the anterior surface of the femoral condyles to form the patellofemoral joint. The posterior patella has a narrower medial and a wider lateral facet. A variable, usually small, odd facet lies along the medial border of the patella.

By displacing the fulcrum of motion of the extensor mechanism anterior to the femur, the patellofemoral articulation produces a mechanical advantage increasing the force of the quadriceps

Passive stabilizers

The patellar ligament and the medial and lateral patellar retinacula form the passive stabilizers of the patella. The retinacula have deep and superficial layers.3., 4. The superficial layers of the retinacula attach to the patella and patellar ligament and extend to the fascia of sartorius medially and to the fascia of the iliotibial band laterally. The deep layers contain thickenings that form ligaments, which provide significant stabilizing support to the patella.

On the medial side, the

Active stabilizers

The four quadriceps muscles form the active stabilizers of the patella. The inferior portions of the vastus medialis and lateralis muscles form small muscle groups with a distinct oblique orientation of their fibres, the vastus medialis obliquus and the vastus lateralis obliquus muscles (Fig. 1). These provide active restraining forces on the patella in the medial and lateral directions, respectively. The vastus medialis obliquus attaches to the distal adductor magnus tendon and inter-muscular

Pathological processes

Anterior knee pain is a common clinical symptom with many potential causes, some of which relate to the patellofemoral articulation (Table 1). The terms used to describe patellofemoral disorders discussed below have been used rather loosely. In particular chondromalacia patellae has sometimes been used as a catch-all phrase to describe patellofemoral pain with or without documented chondral abnormality. The term “patellofemoral pain syndrome” may be used in preference to include multiple

Patellofemoral malalignment and maltracking

Patellofemoral alignment refers to the static relationship between the patella and the trochlea at a given degree of knee flexion. Tracking refers to dynamic patellofemoral alignment during knee motion. Thus, malalignment and maltracking refer to conditions in which there is an imbalance of forces on the patella that produce abnormalities of alignment and tracking, respectively.⁹ This imbalance may result from a combination of variables in bony geometry, function of active and passive

Lateral patella dislocation

Lateral patellar dislocation is a common cause of acute traumatic haemarthrosis in young active patients, usually occurring during sporting activities.³⁹ However, patellar dislocation is usually transient, with patients frequently unaware that it has occurred. Additionally, full examination of the acutely swollen painful knee may be difficult. For these reasons patellar dislocation has been found to be initially clinically unsuspected in as many as 45–73% of cases,40., 41. and MRI findings are

Excessive lateral pressure syndrome

Excessive lateral pressure syndrome refers to a condition in which lateral patellar tilt is dominant with little or no subluxation.⁵⁶ This condition occurs in adolescents and adults often presenting with patellofemoral pain. Imaging studies may reveal cartilage loss, sclerosis and cystic change of the lateral patella and trochlea (Fig. 15). Dynamic studies may show lateral patella tilt, which tends to increase with increasing flexion, but with little subluxation.²⁷

Chondromalacia patellae

The term chondromalacia patellae is properly applied to a syndrome of anterior knee pain, typically in young patients, with initial pathological changes of cartilage softening, swelling and oedema.15., 57. Proposed causes include trauma, chronic stress, patellofemoral instability and anatomic variations in bony morphology. Chondromalacia patellae may be reversible, or may progress to develop patellofemoral osteoarthritis.⁵⁸

Cartilage lesions typically occur along the medial patella at the ridge

Patellofemoral osteoarthritis

Involvement of the patellofemoral compartment in osteoarthritis of the knee is common. Typically the lateral patellofemoral joint is involved in conjunction with either the lateral or medial femorotibial joint. Medial patellofemoral disease may occur in association with medial femorotibial osteoarthritis, but isolated involvement of the medial patellofemoral joint is distinctly unusual. Where osteoarthritis appears to predominate in the patellofemoral compartment with sparing of the

Osteochondritis dissecans

Osteochondritis dissecans of the patella is much less common than osteochondritis of the femoral condyles. It is usually unilateral and typically occurs in males between 15 and 20 years old. The condition is thought to be traumatic in origin, and there is often a history of onset of pain during knee flexion whilst lifting a weight.65., 66.

Osteochondritis dissecans of the patella almost never affects the superior pole and is most commonly seen along the medial patellar facet. On conventional

Dorsal defect of the patella

A dorsal defect of the patella is a well-defined focal defect in the subchondral bone that is confined to the superolateral aspect of the patella. On arthrography and MRI the overlying articular cartilage appears intact and indeed thickens to fill the defect (Fig. 18). This lesion is usually asymptomatic and appears to represent a variant of ossification, possibly within the spectrum of the bipartite patella. All of these features serve to differentiate this lesion from osteochondritis

Bipartite patella

Bipartite patella occurs in approximately 2% of individuals and is much more common in males (Fig. 19). It is usually a bilateral finding. With rare exceptions this anomaly occurs at the superolateral aspect of the patella. The lesion is usually asymptomatic, but can be associated with localized anterior knee pain.⁷¹ Histologically there may be evidence of chondro-osseous tensile failure at the junction with the host bone similar to that seen in Osgood-Schlatter disease and

Conclusion

Anterior knee pain is a common symptom with a large variety of possible causes including pathologies related to the patellofemoral joint. Many of these pathologies have been rather loosely defined and remain incompletely understood because of the complex nature of patellofemoral biomechanical function and dysfunction. Imaging techniques have contributed to the further understanding of these processes, but the goal of imaging under true conditions of everyday physiological function and

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Cited by (140)

Reliability and validity of quantitative ultrasound for evaluating patellar alignment: A pilot study
2024, Journal of Orthopaedic Science
Patellar malalignment is a risk factor of patellofemoral pain. Evaluation of the patellar alignment have mostly used magnetic resonance imaging (MRI). Ultrasound (US) is a non-invasive instrument that can quickly evaluate patellar alignment. However, the method for evaluating patellar alignment via US has not been established. This study aimed to investigate the reliability and validity of evaluating patellar alignment via US.
The sixteen right knees were imaged via US and MRI. US images were obtained at two sites of the knee to measure US-tilt as the index of patellar tilt. Using a single US image, we measured US-lateral distance and US-angle as the index of patellar shift. All US images were obtained three times each by two observers to evaluate reliabilities. Lateral patellar angle (LPA), as the indicators of patellar tilt, and lateral patella distance (LPD) and bisect offset (BO), as the indicators of patellar shift, were measured via MRI.
US measurements provided high intra- (within-day and between days) and interobserver reliabilities with exception of interobserver reliability of US-lateral distance. Pearson correlation coefficient indicated that US-tilt is significantly positively correlated with LPA (r = 0.79), and US-angle is significantly positively correlated with LPD (r = 0.71) and BO (r = 0.63).
Evaluating patellar alignment via US showed high reliabilities. US-tilt and US-angle showed moderate to strong correlation with MRI indices of patellar tilt and shift via MRI, respectively. US methods are useful for evaluating accurate and objective indices of patellar alignment.
An unusual case of traumatic medial eversion-dislocation of the patella: a case report
2022, Journal of ISAKOS
Medial dislocation of patella has been commonly reported as a complication of the surgical release of the lateral patella-femoral ligament. A traumatic medial eversion-dislocation of the patella has not been earlier reported.
We report an unusual case of traumatic medial patellar eversion-dislocation in a young adult patient whose magnetic resonance imaging (MRI) showed a discontinuity in medial and lateral patellar retinacula. However, intraoperatively, the retinacula were found intact, and relocation of the patella was achieved by flipping the patella through a small hole in the patellar tendon. No reconstruction of the ligaments was needed. At 1-year follow-up, the patient achieved full range of movements of the knee, and there were no subjective complaints of instability. In our case, although the patella was medially everted and dislocated, both the retinacula were still intact. Clinicians should be aware that acute traumatic patella medial dislocation and eversion can occur without disruption of the medial or lateral retinaculum. Furthermore, knee MRI may suggest patellar retinacula disruption because of the retinaculum's obscure and tortuous course in patients with these injuries.
Development and validation of a robust patellar reference coordinate system for biomechanical and clinical studies
2020, Knee
Citation Excerpt :
The other landmarks had correlation coefficients ranging from 0.67–0.85 for the inter-class ICC and from 0.45–0.73 for the intra-class ICC. Due to the spread of anterior knee pain, it is vital to identify a local coordinate system for the patellar bone [7,8,10]. To date, no agreement has been found concerning a patellar reference frame, as most present studies have developed their own patellar frame without validating its precision.
This study aimed to develop and validate a reference coordinate system for the human patella, based on the registration of bony landmarks on a computed tomography (CT) scan.
Thirty-three native cadaveric specimens were scanned, and an observer marked a set of seven anatomical landmarks on each of them. Such markers were used to define the reference coordinate system. In order to validate its robustness, statistical distribution of the point registration was then studied. Afterwards, three different observers marked the anatomical landmarks on a sub-sample of six specimens and the intra-observer and inter-observer variability of the point registration was performed.
Results of this study showed the highest values to be 1.46 mm (intra) and 4.08 mm (inter), both observed for the patellar ridge top. The intra-class correlation coefficient (ICC) for inter-observer variability ranked higher than 0.8 for all the landmarks used for the identification of the reference frame, and ranged from 0.4–0.9 for other landmarks.
This study demonstrates low intra-observer and inter-observer variability in the CT registration of landmarks that define and validate a robust coordinate system of the patella that could be used to perform accurate biomechanical and clinical studies.
Varied influence of the femoral or tibial component on quadriceps angles: Verified by imaging studies
2019, Acta Orthopaedica et Traumatologica Turcica
The aim of this study was to evaluate the varied influence of femoral or tibial component on Quadriceps angles (Q-angle) measured with magnetic resonance image (MRI) and full-length standing scanogram (FLSS) techniques.
Two groups of patients were studied. The first group underwent MRI studies and the second group underwent FLSS studies. Two-step procedures were carried out. Knee MRI in 60 consecutive adult patients simply taken for meniscus or ligament injuries were utilized at the first step. The standardized patellar center (PC) and tibial tubercle (TT) on the frontal plane of MRI were positioned. At the second step, the FLSS in other 100 consecutive young adult patients taken for chronic unilateral lower extremity injuries were used for locating the two landmarks from MRI. The Q-angle was then determined on the anterior superior iliac spine, standardized PC, and TT on the FLSS.
For 60 patients, the standardized PC was at the point 42% from the lateral end of the trans-epicondylar line of the femur. The TT was at the point 2 cm distal to the tibial articular surface and 37% from the lateral end of the tibial width. For 100 patients, the Q-angle was an average of 9.5° and 65.2% of the Q-angle was contributed by the upper arm (the femur). Women had a larger Q-angle (10.1° vs. 8.8°, p = 0.02) and a shorter femur (41.1 vs. 44.7 cm, p < 0.001).
The Q-angle is about 9.5° with 65.2% contributed by the femur. The Q-angle may mainly be influenced by the femoral component.
Level IV, Diagnostic Study.
Ultrasonographic assessment of quadriceps and patellar tendon thicknesses in patients with patellofemoral pain syndrome
2019, Acta Orthopaedica et Traumatologica Turcica
Citation Excerpt :
Imaging is particularly useful for excluding alternative diagnoses in the management of PFPS. Plain knee radiography, followed by computed tomography and magnetic resonance imaging are used for the evaluation of knee pain.28,29 Our study is the first to demonstrate the benefits of ultrasonography, which is a non-invasive, easy-to-apply, widely-used imaging modality without exposing the patient to radiation or contrast media, for the diagnosis of PFPS.
The aim of this study was to compare ultrasonographically measured quadriceps and patellar tendon thicknesses between Patellofemoral Pain Syndrome (PFPS) patients and age- and gender-matched healthy controls.
Among patients who presented to physical therapy and rehabilitation outpatient clinic in January–December 2016, 61 volunteers (28 men and 33 women; mean age: 30.79 ± 6.55 years) who were eligible considering the inclusion and exclusion criteria were enrolled. 30 were diagnosed with PFPS, and the remaining were age- and gender-matched healthy volunteers. Mean age was 30.03 ± 5.67 years in healthy subjects and 45.2% were of male gender. The patient group had mean age of 31.57 ± 7.37 years and 46.7% of the patients were male. Q angles were measured at standing, supine and sitting positions. Patellar and femoral tendon thicknesses and areas were measured ultrasonographically. Kujala questionnaire were used to evaluate the functional status of the participants.
No significant difference was detected between groups regarding profession, educational background, and body mass indices (BMI) (p > 0.05). Q angle values were significantly higher in the patient group when compared to controls at standing (17.03 ± 3.84 vs. 13.87 ± 1.75°, p < 0.001), supine (16.20 ± 3.74 vs. 13.45 ± 1.79°, p = 0.001) and sitting (16.50 ± 3.28 vs. 13.71 ± 1.72°, p < 0.001) positions. Kujala score was significantly lower in the PFPS group when compared to controls (70.57 ± 8.37 vs. 98.58 ± 2.05, p < 0.001). Patellar (0.39 ± 0.08 vs. 0.32 ± 0.05 cm, p < 0.001) and quadriceps (0.64 ± 0.10 vs. 0.52 ± 0.09 cm, p < 0.001) tendon thicknesses were significantly higher in the PFPS group when compared to controls. There was no significant difference between groups regarding patellar tendon areas (p > 0.05). Patellar tendon thickness values of ≥0.35 cm were found to have 66.7% sensitivity and 67.7% specificity for PFPS diagnosis in the ROC curve analysis (area under curve: 0.771, 95% confidence interval: 0.655–0.887, p < 0.001). Quadriceps tendon thickness values of ≥0.54 cm were found to have 80% sensitivity and 71% specificity for PFPS diagnosis in the ROC curve analysis (area under curve: 0.824, 95% confidence interval: 0.710–0.939, p < 0.001). In PFPS patients, quadriceps tendon thickness had significant positive correlation with age (r = 0.405, p = 0.027) and BMI (r = 0.450, p = 0.013); and significant negative correlation with Kujala score (r = −0.441, p = 0.015). In the multivariate regression analysis, quadriceps tendon thickness was independently associated with the presence of PFPS (Exp (B): 3.089, 95% confidence interval: 1.344–7.100, p = 0.008).
Our study demonstrates that ultrasonographically measured patellar and quadriceps tendon thicknesses are significantly higher in subjects with PFPS and particularly, quadriceps tendon thickness may be used for the diagnosis.
Level III, Therapeutic Study.
Effects of patellar taping on knee pain, functional disability, and patellar alignments in patients with patellofemoral pain syndrome: A randomized clinical trial
2018, Journal of Bodywork and Movement Therapies
What are the effects of patellar taping on pain, functional disability and patellar alignments in Patellofemoral Pain Syndrome (PFPS)?
Double-blind randomized clinical trial.
Thirty PFPS Patients were randomly divided into two groups, intervention and control.
Intervention: Patients in control group received only the routine physiotherapy. In addition to routine physiotherapy, patellar taping was used in the intervention group. Each patient was treated for 12 sessions over a period of 4 weeks.
The KOOS and VAS questionnaires were used to assess the quality of life (QOL) and pain intensity, respectively. Three components of patellar alignment including Patellofemoral Congruence Angle (PFCA), Lateral Patellofemoral Angle (LPFA) and Lateral Patellar Displacement (LPD) were evaluated using the skyline radiography method.
The results indicated that there was no significant difference between the control and intervention groups for LPD (P = 0.586), PFCA (P = 0.704) and LPFA (P = 0.176) variables. No significant difference was found between the two groups in all items of the KOOS questionnaire. The knee pain intensity was significantly reduced in both the intervention (P < 0.001) and control (P = 0.001) groups at the end of the 4th week.
The results of the present study indicated that patellar taping compared to routine physiotherapy treatments had no beneficial effects on pain reduction, QOL improvement and correction of patellar alignment in PSPS patients.
IRCT201111012851N2.

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ReviewImaging of patellofemoral disorders

Abstract

Introduction

Section snippets

Anatomical and biomechanical considerations

Passive stabilizers

Active stabilizers

Pathological processes

Patellofemoral malalignment and maltracking

Lateral patella dislocation

Excessive lateral pressure syndrome

Chondromalacia patellae

Patellofemoral osteoarthritis

Osteochondritis dissecans

Dorsal defect of the patella

Bipartite patella

Conclusion

Clin Sports Med

Clin Sports Med

Clin Sports Med

Arthroscopy

Clin Radiol

Patellar and quadriceps mechanism

Anatomy of the knee joint lateral retinaculum

Clin Orthop

The supporting structures and layers on the medial side of the knee: an anatomical analysis

J Bone Joint Surg Am

Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee

J Bone Joint Surg [Am]

Classification of lesions of the medial patello-femoral ligament in patellar dislocation

Int Orthop

Soft-tissue restraints to lateral patellar translation in the human knee

Am J Sports Med

Chondromalacia patellae: a system of classification

Clin Orthop

Chondromalacia patellae. A prospective study

J Bone Joint Surg [Am]

Mechanical factors in the incidence of knee pain in adolescents and young adults

J Bone Joint Surg [Br]

Instrumented measurement of patellar mobility

Am J Sports Med

The tangential x-ray investigation of the patellofemoral joint: x-ray technique, diagnostic criteria and their interpretation

Clin Orthop

Roentgenographic analysis of patellofemoral congruence

J Bone Joint Surg [Am]

Roentgenographic and anatomic studies on the femoropatellar joint

Acta Orthop Scand

The sulcus angle and malalignment of the extensor mechanism of the knee

J Bone Joint Surg [Br]

The abnormal lateral patellofemoral angle: a diagnostic roentgenographic sign of recurrent patellar subluxation

J Bone Joint Surg [Am]

The radiographic axial view of the patellofemoral joint: examination in the supine or standing position

Eur Radiol

Patella position in the normal knee joint

Radiology

The modified Insall-Salvati ratio for assessment of patellar height

Clin Orthop

Axial and lateral radiographs in evaluating patellofemoral malalignment

Am J Sports Med

The patellofemoral joint—a critical appraisal of its geometric assessment utilizing conventional axial radiography and computed arthrotomography

Br J Radiol

Diagnosis of patellofemoral malalignment by computed tomography

J Comput Assist Tomogr

Kinematic CT of the patellofemoral joint

AJR Am J Roentgenol

Kinematic CT and MR imaging of the patellofemoral joint

Eur Radiol

Patellar tracking abnormalities: clinical experience with kinematic MR imaging in 130 patients

Radiology

Kinematic MR imaging of the patellofemoral joint: comparison of passive positioning and active movement techniques

Radiology

Patellofemoral joint: identification of abnormalities with active-movement, unloaded versus loaded kinematic MR imaging techniques

Radiology

Patellofemoral relationships in recurrent patellar dislocation

J Bone Joint Surg [Br]

Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging

Radiology

Computed tomography (CT) and CT arthrography

Patellofemoral joint motion: evaluation by ultra-fast computed tomography

Skeletal Radiol

Review
Imaging of patellofemoral disorders