Eur Radiol 10:10511055, Stefanik JJ, Zumwalt AC, Segal NA, Lynch JA, Powers CM (2013) Association between measures of patella height, morphologic features of the trochlea, and patellofemoral joint alignment: the MOST study. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Surgical management procedures can broadly be categorized as soft tissue procedures (lateral release, medial imbrication, and MPFL repair or reconstruction) and bony procedures (tibial tubercle transfer procedures and trochleoplasty). Patella instability in children and adolescents. Several osteotomies have been described including the medializing ElmslieTrillat procedure, the anteromedializing Fulkerson osteotomy, and distalization osteotomy [87]. (27a) Axial and (27b) coronal fat suppressed proton density-weighted images in a patient who experienced recurrent patellar dislocation following surgery. b Patellar alta evaluation using the CatonDeschamps index, which is the ratio between a line measured between the inferior margin of the patellar articular surface and the anterior aspect of the tibial plateau (black line) and the greatest length of the patellar articular surface (white line). (4a) This 3D graphic view of the medial knee with the crural fascia and sartorius (S) muscle incised and reflected demonstrates the main medial contributors to patellar stability. 2010. 2010 Aug;36(4):353-60. doi: 10.1007/s00068-010-9165-2. CT of both knees in 20 flexion demonstrating bilateral shallow trochlear groove (arrows) compatible with dysplasia and bilateral lateral patellar subluxation and lateral tilt. The osteocartilaginous anatomy of the patellofemoral joint provides additional static stabilization to the joint. Am J Sports Med 33:220230, Nikku R, Nietosvaara Y, Aalto K, Kallio PE (2005) Operative treatment of primary patellar dislocation does not improve medium-term outcome: a 7-year follow-up report and risk analysis of 127 randomized patients. At 0 extension, the patellar may lie completely above the level of the trochlea, without direct apposition between the two articular surfaces. However, in the case of acute, focal, lateral patellar pain, a lateral patel - lar sleeve avulsion should be considered and may necessitate advanced imaging for optimal evaluation. MeSH 2. Osteochondral injuries of the inferomedial patella are seen in up to 70% of patellofemoral dislocations. On T2-weighted MR images, sprain is depicted as thickening of retinaculum with signal intensity signifying edema and hemorrhage (Fig. However, patellofemoral tracking is a dynamic process with the spatial relationship between the articular surfaces varying depending on the position of the knee joint [57, 64]. The deep layer of the lateral retinaculum contains thickenings that form ligaments providing stabilizing support to the patella. AJR Am J Roentgenol 169:211215, Buchner M, Baudendistel B, Sabo D, Schmitt H (2005) Acute traumatic primary patellar dislocation: long-term results comparing conservative and surgical treatment. Levy B, Tanaka M, Fulkerson J. 25a) Axial proton density-weighted images at initial injury (left) and 5 months later demonstrate progression of medial retinacular and MPFL scarring (arrows) in this patient with trochlear dysplasia and chronic patellofemoral instability with a history of multiple prior dislocations. Starok M, Lenchik L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Accessibility It is measured at the mid-point of the patella on the axial slices [48]. Adjunctive treatments such as knee aspiration and patellar stabilizing braces have been proposed to decrease swelling and enable early range of motion; however, there is no conclusive evidence for their use [71]. 10 Diederichs G, Issever Ahi S, Scheffler S. MR Imaging of Patellar Instability: Injury Patterns and Assessment of Risk Factors. Patellar maltracking occurs as a result of an imbalance in the dynamic relationship between the patella and trochlea. These are evaluated on most cranial axial image showing cartilage, approximately 3cm above the joint line. 21 Patellar dislocation not only has a high recurrence rate 51 but also readily causes articular cartilage damage, osteochondral fractures, and patellofemoral arthritis, which can ultimately lead to motor dysfunction and pain. 1997 Jun;168(6):1493-9. doi: 10.2214/ajr.168.6.9168713. Another method is the CatonDeschamps index. Insights into Imaging A tight lateral retinaculum can tilt the patella leading to increased pressure on the lateral facet causing pain (Ficat). The objective of this paper was to describe the anatomy of the stifle joint (Articulatio genus) of the pampas deer (Ozotoceros bezoarticus, Linnaeus, 1758) by dissection and imaging studies. Stretching exercises for Patellofemoral pain. The typical injury pattern is a tear of the medial patellofemoral ligament (MPFL) and bone bruises of the patella and the lateral femoral condyle. Cookies policy. Axial PDFS MR image showing MPFL disruption (open arrow) and trochlear dysplasia (arrowheads). Provided by the Springer Nature SharedIt content-sharing initiative. Acta Orthop Scand 68:419423, Deie M, Ochi M, Sumen Y, Adachi N, Kobayashi K, Yasumoto M (2005) A long-term follow-up study after medial patellofemoral ligament reconstruction using the transferred semitendinosus tendon for patellar dislocation. eCollection 2015. Patellar tracking refers to the dynamic relationship between the patella and trochlea during knee motion [1]. Patellar maltracking: an update on the diagnosis and treatment strategies, https://doi.org/10.1186/s13244-019-0755-1, http://creativecommons.org/licenses/by/4.0/. LTI < 11 degrees indicates dysplasia. Because as noted above, the femoral bone bruise occurs as the patella moves forward during reduction, bone bruises at the lateral femoral condyle always course anteriorly from the site of any femoral chondral injury that may be present. There is agreement, however, that the MPFL is almost always injured with lateral patellar dislocations4. Post WR, Teitge R, Amis A (2002) Patellofemoral malalignment: looking beyond the viewbox. There are numerous techniques reported in literature and commonly used to reconstruct the medial sided soft tissue constraints. Jibri, Z., Jamieson, P., Rakhra, K.S. 4. Osteochondral fractures are common in acute or recurrent transient lateral patellar dislocation, seen in up to 70% of cases. 2021;50(7):1399-409. This procedure involves removal of cancellous bone beneath the trochlea followed by fixation of the articular surface [88, 89]. As is typical, a bone bruise extends anteriorly (arrowheads) from the site of the chondral defect. AJR Am J Roentgenol 187:13321337, White BJ, Sherman OH (2009) Patellofemoral instability. First, a line is drawn paralleling the posterior femoral condyles surfaces. It can be difficult to determine the deepest part of the trochlear groove when assessing the TT-TTG in the presence of trochlear dysplasia; therefore, an alternative method for assessing tibial tubercle position was proposed measuring the distance in reference to the posterior cruciate ligament and not to the trochlea (tibial tubercle-posterior cruciate ligament distance [TT-PCL]), with proposed pathologic threshold of 21mm [42, 43]. Am J Sports Med 40:11191125, Boutris N, Delgado DA, Labis JS, McCulloch PC, Lintner DM, Harris JD (2018) Current evidence advocates use of a new pathologic tibial tubercle-posterior cruciate ligament distance threshold in patients with patellar instability. b Trochlear dysplasia (9 inclination), Facet asymmetry assessment for trochlear dysplasia on axial MRI. Med Sci Sports Exerc 35:20432047, Steiner T, Parker RD (2009) Patella: subluxation and dislocation. Patellar tilt assessment. The goal of patellar instability treatment is to achieve a stable, functional, and pain-free knee and ultimately to halt or slow the development of osteoarthritis. Trochlear depth=[(a+b)/2]c, Lateral trochlear inclination measurement on axial MRI. 9). 2 Baldwin JL. The distance from the tibial tubercle to the trochlear groove (TT-TG) provides a quantitative evaluation of excessive lateralization of the tibial tuberosity.7, (10a) Axial image of the knee with superimposition of the tibial tubercle from another slice (yellow outline). An official website of the United States government. also supported our data in a magnetic resonance imaging (MRI) study of 82 patients with the diagnosis of lateral patella dislocation and found that 76% of medial retinacular/MPFL disruption occurred at its patellar insertion site, 49% occurred at the femoral attachment site, 30% showed injury of the MPFL at mid-substance, and 48% . Despite this, there remains considerable variation in surgical technique including graft choice, position, and tension making the literature difficult to compare [8, 15, 79,80,81,82,83,84,85,86]. Knee CT images in the early post-operative period in a 19-year-old male with history of patellar maltracking. Epub 2023 Feb 7. It can not only detect any underlying morphological risk factors but also look for structural damage associated with maltracking including patellofemoral articular cartilage loss, osteochondral defects, or damage to the medial patellar stabilizers [4, 5]. It is therefore helpful in surgical planning. Kim et al. High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns . In either case, careful search for possible displaced osteochondral fragments is necessary, as surgery is often indicated in such patients. 2002 Dec;225(3):736-43. doi: 10.1148/radiol.2253011578. It is a ratio between the patellar tendon length (along the inner surface of the tendon) and the diagonal patellar height [27]. Normal = 0.8 to 1.2. Risk factors for recurrent patellar dislocations include 5: The presence of an abnormal medial patellar retinaculum should suggest the diagnosis of transient lateral patellar dislocation 1. Medial patellar chondral injuries may occur during either the dislocation or reduction phases of injury. is a term coined for anatomic characteristics that lead to an increased Q angle and an exacerbation of patellofemoral dysplasia. Crossref, Medline, Google Scholar; 32 Starok M, Lenchikl L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Please enable it to take advantage of the complete set of features! Radiology 225:736743, Kirsch MD, Fitzgerald SW, Friedman H, Rogers LF (1993) Transient lateral patellar dislocation: diagnosis with MR imaging. 1835 31 - 40 27 30.0 41 - 50 22 24.4 50 + 4 4.4 Total 90 100.0 Age Distribution Number Percent Sex Female 19 21.1 Male 71 78.9 3 Dirim B, Haghighi P, Trudell D et al. Trochleoplasty is rarely performed in this country and is reserved for significant dysplasias or when other surgical options have been insufficient in restoring patellofemoral stability. MRI Web Clinic, August 2010. https://radsource.us/patella-alta-and-baja/. Long term follow up studies in patients who have undergone a lateral release have shown an increased incidence of patellofemoral arthritis. In order for the patella to engage with the femoral trochlea, a higher degree of flexion than normal is needed. Given the lack of history of direct trauma, a reliable diagnosis can be made. Magnetic resonance imaging (MRI) is a vital tool in evaluating the potential cause(s) of anterior knee pain due to the complexity of the structure and biomechanics of the knee. ADVERTISEMENT: Supporters see fewer/no ads. {"url":"/signup-modal-props.json?lang=us"}, Moodaley P, Hng J, Hacking C, et al. On the other hand, the PTI is significantly altered with knee flexion [37]. Axial PDFS left knee MR image, demonstrating the method used for the measurement of trochlear depth. Dejour et al. Stretching this ligament keeps the patella in place and the ligament healthy. Identifying edema at the superolateral aspect of Hoffas fat pad on MRI should prompt the reporting radiologist to look for features of patellar maltracking. The decreased patellar contact area decreases stability particularly in shallow degrees of flexion and thus predisposes to lateral patellar subluxation. volume10, Articlenumber:65 (2019) The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. Lateral patellar dislocation is a common clinical entity with a characteristic MR appearance. Unable to process the form. The lateral patellar retinaculum presents a superficial layer attached medially to the patella and patellar ligament, and extending laterally to the iliotibial band and vastus lateralis muscle fascia (Fig. Magnetic Resonance Imaging Characteristics of the Medial Patellofemoral Ligament Lesion in Acute Lateral Patellar Dislocations Considering Trochlear Dysplasia, Patella Alta, and Tibial Tuberosity-Trochlear Groove Distance (2011) ISBN: 9780781778602 -. . Sports Med Arthrosc 15:5760, Nam EK, Karzel RP (2005) Mini-open medial reefing and arthroscopic lateral release for the treatment of recurrent patellar dislocation: a medium-term follow-up. Acta Orthop Belg 72:6571, Panagopoulos A, van Niekerk L, Triantafillopoulos IK (2008) MPFL reconstruction for recurrent patella dislocation: a new surgical technique and review of the literature. Medial patellar. It has proven to be both sensitive and specific in the detection of hyaline cartilage abnormalities [4]. Both knees are scanned simultaneously. [Google Scholar] 6. Seventeen patients with patellar retinacular ligament injuries were evaluated with magnetic resonance (MR) imaging. The axial proton density-weighted image reveals a large osteochondral shearing injury involving the mid to medial patella (arrowheads). Diagnosis is made clinically with pain with compression of the patella and moderate lateral facet tenderness and sunrise knee radiographs will often show patellar tilt in the lateral direction. (11a) The depth of the trochlear groove is measured by drawing a line from the most anterior position of the medial trochlea to the lateral trochlear anterior cortex. Asymmetry of <40% suggests trochlear dysplasia [24]. A commonly used one is the InsallSalvati ratio of patellar tendon length: patellar length. (19a) The corresponding STIR coronal image reveals the large displaced osteochondral fragment (arrow) at the lateral aspect of the lateral femoral condyle. The MPFL is best seen on axial MRI on the slice just distal to the VMO. lateral patellar retinacular sleeve, mak-ing this particular avulsion a rare oc-currence. official website and that any information you provide is encrypted This treatment generally consists of the use of anti-inflammatory medications, a short period of immobilization (36weeks) followed by a progressive physiotherapy regimen with focus on range of motion, closed chain exercises, and vastus medialis obliquus strengthening [16, 65,66,67,68,69,70]. This is often secondary to an underlying structural abnormality. The patella itself is shaped as an inverted triangle and is embedded in the quadriceps tendon, making it the largest sesamoid bone in the body [6]. Osteochondral injuries to the inferomedial patella may be the result of impaction during dislocation or shearing with reduction. The most accepted indication for surgical management of patellar instability is the presence of a large displaced osteochondral fracture or loose body. Recent literature does not encourage the use of lateral release, since this can increase patellar instability. Methods MRI studies taken at one imaging site between January, 2007 to January, 2008 with the final diagnosis of patella . Am J Sports Med. Laxity of the medial stabilizers will lead to increasing instability over time. Patella alta assessment. The trochlear groove and patella may have abnormal morphology that predisposes to patellar dislocation. no financial relationships to ineligible companies to disclose. Magn Reson Med Sci 17:195202, Elias DA, White LM (2004) Imaging of patellofemoral disorders. b Axial MRI at the level of the tibial tuberosity. An increased tibial tubercletrochlear groove (TT-TG) indicates a lateralized tibial tuberosity, or a medialized trochlear groove [38]. Am J Orthop (Belle Mead NJ) 46:290300, Dejour H, Walch G, Neyret P, Adeleine P (1990) Dysplasia of the femoral trochlea. Nearly 50% of all first-time dislocators will sustain further dislocations. AJR Am J Roentgenol 1997; 168:1493-1499. The literature in this field has been extremely heterogeneous, and this has made clinical guidelines difficult to produce. Stress and shear forces that follow can result in cartilage damage and the development and evolution of osteoarthritis [57]. Acute Osteochondral Fractures in the Lower Extremities - Approach to Identification and Treatment. Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella Injury to the medial retinaculum, MPFL, and VMO may be identified at MR imaging after acute LPD. The patella remains laterally shifted (blue arrow) and an osteochondral injury of the medial patella (arrowheads) is apparent. The patella becomes unstable and undergoes a transient, violent lateral displacement. Acta Orthop 76:699704, Nikku R, Nietosvaara Y, Kallio PE, Aalto K, Michelsson JE (1997) Operative versus closed treatment of primary dislocation of the patella. During this dislocation phase of injury, shearing forces can damage the articular surfaces of either the patella or the lateral femoral condyle. The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. J Orthop Sports Phys Ther 2017;47(10):815. doi:10.2519/ jospt.2017.6616 . Reference article, Radiopaedia.org (Accessed on 02 May 2023) https://doi.org/10.53347/rID-27273, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":27273,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/lateral-patellar-dislocation/questions/2391?lang=us"}, Case 14: transient lateral patellar dislocation, see full revision history and disclosures, anterior cruciate ligament avulsion fracture, posterior cruciate ligament avulsion fracture, Ahlback classification system in assessing osteoarthritis of the knee joint, Kellgren and Lawrence system for classification of osteoarthritis, anterior cruciate ligament mucoid degeneration, MRI grading system for meniscal signal intensity, medial retinacular abnormalities (ranging from strain to complete disruption) with adjacent periligamentous edema and hemorrhage, lateral displacement of patella (not necessarily seen in transient dislocation), medial patellar contusion +/- corresponding lateral femoral condyle contusion, direct trauma to lateral knee:normally no patellar contusion. A buckle transducer was clamped on the lateral patellofemoral ligament and the transducer was calibrated to zero with the knee at full extension. (13a) A line is drawn between the cortex of the lateral trochlear facet on the most superior axial image showing cartilage. Although you may feel that being asked to make the specific diagnosis of lateral patellar dislocation from a single image is unrealistic, the coronal view in fact reveals a classic and highly characteristic appearance, allowing the diagnosis to be made with confidence. Patellar maltracking: an update on the diagnosis and treatment strategies. Early diagnosis is essential, as chronic maltracking will lead to patellofemoral cartilage damage and osteoarthritis [3]. Patella alta is related to a long patellar tendon and is considered a major factor associated with reduced contact area at the patellofemoral joint and a major contributor to patellar instability [33]. Int Orthop 34:305309, Biedert RM, Albrecht S (2006) The patellotrochlear index: a new index for assessing patellar height. Tears of the medial retinaculum and the MPFL are commonly present at both the patellar and femoral attachments, though tears of the transverse band of the MPFL are more likely at the femoral attachment. CAS lateral patellar retinaculum tear or invasion. 7 Balcarek P, Jung K, Frosch KH, Sturmer KM. Objective: Must rule out a tight iliotibial band (ITB) and weak quadriceps muscles (Juhn). ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. (7a) A coronal T1-weighted image at the level of the patella demonstrates blending of fibers of the VMO with the MPFL superiorly. Radiology 216:858864, Biedert RM, Tscholl PM (2017) Patella alta: a comprehensive review of current knowledge. Knee Surg Sports Traumatol Arthrosc 26:27332742, Hingelbaum S, Best R, Huth J, Wagner D, Bauer G, Mauch F (2014) The TT-TG Index: a new knee size adjusted measure method to determine the TT-TG distance. However, the patella starts to engage with the trochlea by 30 and is typically completely engaged by 45. AJR Am J Roentgenol. The patella has 4 different planes of motion: flexionextension, mediallateral rotation, mediallateral patellar tilt, and mediallateral patellar shift. J Bone Joint Surg Am 85-A:12381242, Article 3. At less than 30 of flexion, asymptomatic knees may demonstrate physiologic patellar tilt or subluxation. To provide the highest quality clinical and technology services to customers and patients, in the spirit of continuous improvement and innovation. Acute patellar dislocation (APD) is a common injury in children, accounting for up to 16% of acute knee hemarthroses. 2023 Lineage Medical, Inc. All rights reserved, Knee & Sports | Lateral Patellar Compression Syndrome. The patellar tendon may tear when the knee is bent and the foot planted, like when landing from a jump or . Our study focus was to evaluate medial patellofemoral ligament (MPFL) injury patterns and associated knee pathology using Magnetic Resonance Imaging studies. (24a) Scarring of the medial stabilizers (asterisk) often leads to healing in a more superior and lateral location (long arrow) leading to persistent medial instability, laxity and malalignment even after the patella has been repositioned. CAS U.S. Army Health Clinic Grafenwoehr U.S. Army Health Clinic Grafenwhr is located on Tower Barracks and provides quality ambulatory care for more than 15,000 Soldiers and their families, while coordinating and facilitating inpatient and specialty care with nearby German host nation medical facilities and DoD partners. Radiology 216:582585, Ward SR, Terk MR, Powers CM (2007) Patella alta: association with patellofemoral alignment and changes in contact area during weight-bearing. The angle between the two lines is the lateral trochlear inclination (LTI). The main morphological features associated with patellar maltracking are trochlear dysplasia, lateralization of the tibial tuberosity, patella alta, and lateral patellar tilt. Additionally, return to sport can be as low as 45%, leaving many patients searching for further management options [12]. However, the use of this method is not widespread. Lastly, a sulcus-deepening procedure known as trochleoplasty may be indicated in the patient with significant trochlear dysplasia and recurrent instability. Subluxation and dislocation: recurrent. The posterior articulating surface of the patella is composed of two facets, a medial and lateral facet, separated by a vertical ridge, and in 30% of the population, there is a third facet, the odd facet, most medially. The VMO is active, not only in full extension but also at 30 degrees and up to 100 degrees of flexion. In our experience, injuries to the transverse band most often involve the femoral attachment, whereas injuries to the oblique decussation and associated medial retinacular structures are more common at the patellar attachment. The pages that follow contain general guidance on the diagnosis and treatment of chronic nontraumatic knee pain. The discrimination between low-grade and high-grade dysplasia is important because prognosis and treatment may depend upon the severity of trochlear dysplasia. Each of the mentioned assessment methods of patella alta has its own advantages and limitations. MRI is the imaging modality of choice in the assessment of patellar maltracking, as a virtue of what it can reveal (Table1). Bookshelf Radiology. MRI has been found to be 85%-92% sensitive for diagnosing MPFL injury (Seeley, 2013). 0000070933 00000 n 0000192215 00000 n 0000212094 00000 n

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