Clin Orthop Relat Res 144:1626, Elias DA, White LM, Fithian DC (2002) Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. This is measured on the sagittal MRI images at the point where the patella is at its greatest length. J Pediatr Orthop 37:484490, Parikh SN, Lykissas MG, Gkiatas I (2018) Predicting risk of recurrent patellar dislocation. Clin Biomech (Bristol, Avon) 19:10401047, Horton MG, Hall TL (1989) Quadriceps femoris muscle angle: normal values and relationships with gender and selected skeletal measures. This allows for greater detailed evaluation of the patellar and trochlear morphology, patellofemoral relationship, and status of the joint. (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. Thawait SK, Soldatos T, Thawait GK, Cosgarea AJ, Carrino JA, Chhabra A. Skeletal Radiol. 7,14 While plain radiography is an important tool to diagnose APD, magnetic resonance imaging (MRI . Between 15 and 45% of patients will develop recurrent patellar instability after acute dislocation, which is both functionally limiting and painful [17,18,19,20]. 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). Arthroscopy 35:537543, Mountney J, Senavongse W, Amis AA, Thomas NP (2005) Tensile strength of the medial patellofemoral ligament before and after repair or reconstruction. This is often secondary to an underlying structural abnormality. In addition, symptomatic knees may demonstrate normal engagement between the patella and trochlea beyond 30 of flexion. Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. The patella remains laterally subluxed and tilted, and the patient has an abnormally shallow trochlear groove (line). A distance between the tibial tubercle and the trochlear groove of less than 15 mm is considered normal. There is a degree of variability in the literature about what is considered an abnormally high TT-TG. Unauthorized use of these marks is strictly prohibited. It has been suggested that fat impingement occurs between the lateral femoral condyle and the posterior aspect of the patellar tendon [54]. PMC When the knee moves slightly out of place or becomes tilted in the joint, it can cause tension and pain in the lateral retinaculum. In the setting of osseous patellar malalignment, an osseous procedure such as tibial tubercle transfer osteotomy can be performed (Fig. Kamel S, Kanesa-Thasan R, Dave J et al. (9a) The Insall-Salvati Index is determined by dividing the length of the patellar tendon (PT) by the length of the patella (PL). At the time the article was created Aditya Shetty had no recorded disclosures. They include: pain with compression of patella and moderate lateral facet tenderness, inability to evert the lateral edge of the patella, mainstay of treatment and should be done for extensive period of time, closed chain short arc quadriceps exercises, pain refractory to extensive rehabilitation, ideal candidate has no symptoms of instability, medial patellar glide of less than one quadrant, lateral patellar glide of less than three quadrants, only elevate 1 cm or else risk of skin necrosis, indicated only for instability with lateral translation (not isolated lateral tilt), viewing through superior portal will show medial facet does not articulate with trochlea at 40 degrees of knee flexion, postoperatively the patella should be able to be, patellar instability with medial translation, Spontaneous Osteonecrosis of the Knee (SONK), Osgood Schlatter's Disease (Tibial Tubercle Apophysitis), Anterior Superior Iliac Spine (ASIS) Avulsion, Anterior Inferior Iliac Spine Avulsion (AIIS), Proximal Tibiofibular Joint Ganglion Cysts, Pre-Participation Physical Exam in Athlete, Concussions (Mild Traumatic Brain Injury). Thus, imaging at positions both less than and greater than 30 can be used to avoid missing maltracking that might be captured at only certain degrees of flexion [64]. 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% . Clin Radiol 59:543557, Ali SA, Helmer R, Terk MR (2010) Analysis of the patellofemoral region on MRI: association of abnormal trochlear morphology with severe cartilage defects. Bookshelf 2023 Apr;47(4):973-981. doi: 10.1007/s00264-023-05707-y. Such patients are generally treated with immobilization for 3 to 6 weeks. VMO dysplasia may play a role in patellofemoral instability. Radiology 187:205212, Jibri Z, Martin D, Mansour R, Kamath S (2012) The association of infrapatellar fat pad oedema with patellar maltracking: a case-control study. The patellofemoral joint has two primary functions; firstly, it acts as an anatomic pulley to provide mechanical advantage for the extensor mechanism and, secondly, to reduce friction between the extensor mechanism and the femur. Skeletal Radiol. In either case, careful search for possible displaced osteochondral fragments is necessary, as surgery is often indicated in such patients. Open Orthop J. Other structures combine to form the region referred to as the medial retinaculum (MR) more anteriorly. Fluid extending into the VMO myotendinous junction is generally seen in the setting of coexisting MPFL/retinacular tears. An imbalance of forces acting on the patellofemoral joint due to abnormal bony geometry or altered function of the active and passive soft tissue restraints may result in abnormalities of alignment and tracking of the patella. 2011;39(8):1756-1761. The authors declare that they have no competing interests. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Medial patellofemoral ligament: cadaveric investigation of anatomy with MRI, MR arthrography, and histologic correlation. The lateral retinaculum appears as a hyperechoic band originating from the iliotibial band and the vastus lateralis muscle. (2011) ISBN: 9780781778602 -. However, it lacks sensitivity with 40% of sizable osteochondral lesions being missed on initial presentation after patellar dislocation [16]. Because the knee is flexed in dislocation, the patella impacts upon the weightbearing surface of the lateral femoral condyle. Clin J Sport Med 15:6266, Colvin AC, West RV (2008) Patellar instability. Osteochondral injuries to the inferomedial patella may be the result of impaction during dislocation or shearing with reduction. Additionally, complex injuries to bone, cartilage, and ligaments may occur. The typical injury pattern is a tear of the medial patellofemoral ligament (MPFL) and bone bruises of the patella and the lateral femoral condyle. Axial PDFS MR image showing MPFL disruption (open arrow) and trochlear dysplasia (arrowheads). Because of the transient and brief nature of lateral patellar dislocations, the diagnosis is frequently unrecognized by both patients and clinicians. Yu JS, Goodwin D, Salonen D, Pathria MN, Resnick D, Dardani M, Schweitzer M. AJR Am J Roentgenol. It was shown that certain features of patellar maltracking (increased sulcus angle, lateral patellar tilt, and a higher patellar tendon to patellar length ratio) are associated with cartilage loss and bone marrow lesions [59]. In this section, we will emphasize the role of MRI and discuss how CT can also have value when assessing patellar maltracking. MRI is the imaging modality of choice in the assessment of patellar maltracking, as a virtue of what it can reveal (Table1). Prior lateral patellar dislocation: MR imaging findings. Note the edema in the superolateral aspect of Hoffas fat pad (arrow). Springer, New York, pp 1529, Cash JD, Hughston JC (1988) Treatment of acute patellar dislocation. Am J Sports Med 14:3945, Ward SR, Powers CM (2004) The influence of patella alta on patellofemoral joint stress during normal and fast walking. The above video demonstrates the mechanism of injury in patellar dislocation. This results in a slightly superolateral direction of pull on the patella by the quadriceps. Check for errors and try again. This is the ratio between a line measured between the inferior margin of the patellar articular surface and the anterior aspect of the tibial plateau and the greatest length of the patellar articular surface. In type A, the trochlear preserves its concave shape but has shallow trochlear groove; type B is flattened or convex trochlea; in type C, the medial facet is hypoplastic (facet asymmetry) with high lateral facet, resulting in flattened joint surface in an oblique plane; and type D shows a cliff pattern with type C features and a vertical link between the medial and lateral facets. Am J Sports Med 14:117120, Smith TO, Donell S, Song F, Hing CB (2015) Surgical versus non-surgical interventions for treating patellar dislocation. (20a) A fat-suppressed proton density-weighted sagittal image in a patient following patellar dislocation reveals an osteochondral injury with a chondral defect (arrows) at the lateral weightbearing surface of the lateral femoral condyle, a finding seen in only 5% of patients. Concave impaction deformity of the inferomedial patella is a specific sign of prior LPD. Objective: This prospective study is designed to detect changes in the treatment of ruptured intracranial aneurysms over a period of 17 years. Additionally, MRs ability to delineate the extent of injury and predisposing factors is important in patient care and surgical planning. Reconstruction of the MPFL has recently become an increasingly popular procedure for recurrent lateral patellar instability. 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. Clinical History: A 23 year-old female presents with medial knee pain following a twisting injury. The medial patellar retinaculum and MPFL are best seen on MRI on the axial fluid-sensitive sequences. Patellar tendon lateral femoral condyle friction syndrome is one of several entities that result in anterior knee pain and in which abnormalities of the patellar fat pads are found on MR imaging. Additional passive stabilizers include the medial patellotibial ligament (MPTL) and the medial patellomeniscal ligament (MPML). [Nov;2019 . AJR Am J Roentgenol 179:11591166, Zhang GY, Zheng L, Ding HY, Li EM, Sun BS, Shi H (2015) Evaluation of medial patellofemoral ligament tears after acute lateral patellar dislocation: comparison of high-frequency ultrasound and MR. Eur Radiol 25:274281, Tecklenburg K, Dejour D, Hoser C, Fink C (2006) Bony and cartilaginous anatomy of the patellofemoral joint. 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. The medial patellar retinaculum is part of the anterior third of the medial joint capsule. Am J Sports Med. Physical therapy is directed to increasing range of motion and to strengthening the VMO and quadriceps muscles. Less commonly, a direct laterally or medially orientated blow to the patella can precipitate dislocation. Excessive lateralization of the tibial tuberosity allows the patella to be pulled laterally in flexion and is considered to be a risk factor for instability. The trochlear groove and patella may have abnormal morphology that predisposes to patellar dislocation. Bull NYU Hosp Jt Dis 67:2229, Dupuy DE, Hangen DH, Zachazewski JE, Boland AL, Palmer W (1997) Kinematic CT of the patellofemoral joint. It is the percentage of the medial (a) to the lateral (b) trochlear facet length (a/b100%). 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]. Epub 2023 Feb 7. PFA of 0 or if it opens medially (negative value) is considered abnormal indicating lateral patellar tilt [27, 48]. AJR Am J Roentgenol 161:109113, Lance E, Deutsch AL, Mink JH (1993) Prior lateral patellar dislocation: MR imaging findings. A newer method to assess for patella alta is the patellotrochlear index (PTI), which is measured in the midsagital MRI as the ratio of the length of trochlear cartilage engaged with the patella to the patellar cartilage length [36]. Patellar maltracking is a disorder that often affects the young active individuals. The marrow edema and medial patellofemoral ligament (MPFL) injury pattern above are virtually pathognomonic of a transient lateral patellar dislocation, as little else will cause such an appearance. Medial patellar chondral injuries may occur during either the dislocation or reduction phases of injury. Injury of the superior peroneal retinaculum (SPR) occurs with peroneal dislocation through forceful ankle dorsiflexion and concomitant reflex peroneal muscle contraction. 1997 Jun;168(6):1493-9. doi: 10.2214/ajr.168.6.9168713. PTI of less than 12.5% suggests the presence of patella alta. A bone bruise of the lateral femoral condyle (asterisk) and an abnormally shallow trochlear groove (red line) are also indicated. An inclination angle of less than 11 indicates trochlear dysplasia [32]. Epidemiology Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in sports activities. Int J Sports Med 29:359365, Smith TO, Walker J, Russell N (2007) Outcomes of medial patellofemoral ligament reconstruction for patellar instability: a systematic review. Bone bruise in acute traumatic patellardislocation: volumetric magnetic resonance imaging analysis with follow-up mean of 12 months. a Normal trochlea. A bone bruise occurs anterior to this site of impaction as the patella reduces with knee extension. Clin Sports Med 21:521546 x, Article Skeletal Radiol 38:785790, Campagna R, Pessis E, Biau DJ et al (2012) Is superolateral Hoffa fat pad edema a consequence of impingement between lateral femoral condyle and patellar ligament? In the seven patients with hyperextension injuries, three had associated meniscal and cruciate ligament tears. The axial proton density-weighted image reveals a large osteochondral shearing injury involving the mid to medial patella (arrowheads). Patellar instability: Assessment on MR images by measuring the lateral trochlear inclination-initial experience. Skeletal Radiology 39:7, 675-682. Reference article, Radiopaedia.org (Accessed on 02 May 2023) https://doi.org/10.53347/rID-54735, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":54735,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/lateral-patellar-retinaculum/questions/2393?lang=us"}. The MCL is beneath the deep crural fascia (layer 1), from which it is separated by a variable amount of fat (Fig. If the lateral retinaculum tendon is tight enough to pull the patella out of the trochlear groove, a lateral release procedure can loosen the tissue and correct the patellar malalignment. Unable to load your collection due to an error, Unable to load your delegates due to an error. 5). 2020;49(6):1642-50. AJR Am J Roentgenol 167:339341, Caton JH, Dejour D (2010) Tibial tubercle osteotomy in patello-femoral instability and in patellar height abnormality. Am J Sports Med. The literature in this field has been extremely heterogeneous, and this has made clinical guidelines difficult to produce. With knee extension and subsequent reduction, the patella bounces back into position and in doing so, the medial patella impacts against the non-weightbearing anterolateral aspect of the lateral femoral condyle, resulting in the characteristic marrow edema pattern. These morphological risk factors can be assessed using methods similar to those on MRI as detailed in the prior sections of this article. (17a) An axial T2 fat-suppressed image in another patient reveals a fluid filled gap (short arrow) at the site of attachment of the medial retinaculum. Rev Bras Ortop 46:160164, LeGrand AB, Greis PE, Dobbs RE, Burks RT (2007) MPFL reconstruction. The medial patellofemoral ligament (MPFL) is a condensation of the medial capsule of the knee joint. On the other hand, the PTI is significantly altered with knee flexion [37]. Arthroscopy 32:929943, Dejour D, Saggin P (2010) The sulcus deepening trochleoplastythe Lyons procedure. 11 Lind M, Jakobsen B, Lund B, et al. For first-time dislocators without intra-articular loose bodies or chondral injury, a trial of nonoperative therapy is indicated. Zaid Jibri. The convex articular surface of the patella places it at risk for chondral injury in either the dislocation or the reduction phases of injury. This site needs JavaScript to work properly. 3). Eleven gave a history of recurrent patellar dislocation. Medial retinacular complex injury in acute patellar dislocation: MR findings and surgical implications. MR imaging can help define patellar retinacular and associated osteochondral injuries, which may be clinically useful information. A ratio > 1.3 indicates patella alta. The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. Skeletal Radiol 48:387393, Schoettle PB, Zanetti M, Seifert B, Pfirrmann CW, Fucentese SF, Romero J (2006) The tibial tuberosity-trochlear groove distance; a comparative study between CT and MRI scanning. Lateral patellar compression syndrome is the improper tracking of the patella in the trochlear groove generally caused by a tight lateral retinaculum. 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. (23a) In this patient with recurrent patellofemoral dislocations, there are findings of subchondral degeneration (arrow) from recurrent impaction and chondral shearing injuries to the inferolateral femoral condyle. In acute traumatic lateral patellar dislocation, it is not only the patella that dislocates. Bethesda, MD 20894, Web Policies Cite this article. PubMedGoogle Scholar. This is an arthroscopic surgery ( a knee "scope" which is performed through 3 small incisions ( about inch each) around the knee. Radiology 263:469474, Subhawong TK, Eng J, Carrino JA, Chhabra A (2010) Superolateral Hoffas fat pad edema: association with patellofemoral maltracking and impingement. The conditions are presented anatomicallyanterior, lateral, medial, or posteriorwith common etiologies, history and physical exam findings, and diagnosis and treatment options for each (see Table, page 28). Am J Sports Med 45:10591065, Brossmann J, Muhle C, Schrder C et al (1993) Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging. The TT-TG distance can be influenced by the degree of knee flexion (reduces with flexion), and it is also smaller upon weight bearing [41]. These measurements are not routinely recorded in the MRI report, but in select situations may be helpful in quantifying low-grade versus high-grade dysplasia. Additionally, in this degree of flexion, the quadriceps tendon itself engages the proximal trochlear groove and participates in force distribution [8,9,10]. 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]. Knee Surg Sports Traumatol Arthrosc 15:13011314, Tom A, Fulkerson JP (2007) Restoration of native medial patellofemoral ligament support after patella dislocation. 9 Lippacher S, Dejour S, Elsharkawi M, et al. A lateral patellar sleeve fracture can be misdiagnosed J Bone Joint Surg Am 85-A:12381242, Article 3. PubMed Central Both knees are scanned simultaneously. The Biomechanics of Medial Patellofemoral Ligament Repair Followed by Lateral RetinacularRelease. Google Scholar, Nakagawa S, Kadoya Y, Kobayashi A, Tatsumi I, Nishida N, Yamano Y (2003) Kinematics of the patella in deep flexion. There is edema of the medial patella and of the lateral femoral condyle (arrow), consistent with bone contusion due to recent lateral patellar dislocation. government site. On the other hand, there are static MRI measurements that are routinely used as indicators of patellofemoral alignment during knee movement [30, 31]. 5. The lateral retinaculum is a ligament that helps hold your patella, or kneecap, in place. Surgical indications following patellar dislocation include the presence of a chondral or osteochondral body, significant rupture of the medial stabilizers most importantly the MPFL, a persistent laterally subluxed patella, or a second dislocation injury in a patient with malalignment or dysplasia. 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]. Focal Defect at the LPR on Clinical Knee MRI and a Cadaveric Study Musculoskeletal Imaging Original Research. It is therefore recommended that radiologists include measurement of TT-TG in reports on patients who undergo MRI for patellar instability. 4). Recent literature does not encourage the use of lateral release, since this can increase patellar instability. The purpose of this article is to discuss the evaluation of patellar maltracking providing an update on the imaging assessment and also a synopsis on the management options. Given the lack of history of direct trauma, a reliable diagnosis can be made. Subluxation and dislocation: recurrent. 2010 Aug;36(4):353-60. doi: 10.1007/s00068-010-9165-2. This can provide a road map of developing a treatment strategy that would be primarily aimed at stabilizing the patellofemoral joint and halt the progression of cartilage loss. It is measured at the mid-point of the patella on the axial slices [48]. Patellar tracking refers to the dynamic relationship between the patella and trochlea during knee motion [1]. It is the angle between a line tangential to the subchondral bone of the posterior aspect of the femoral condyles and a line along the lateral trochlear facet. Twenty-six pelvic limbs were used for gross dissection, and four stifle regions from two animals were used for radiography and magnetic resonance imaging (MRI). The knee then was flexed 30, 60, 90, and 120, and the transducer recorded changes in tension within the lateral patellofemoral . 1). 4 Sanders TG, Morrison WB, Singleton BA, Miller MD, Cornum KG. Medial retinacular complex injury in acute patellar dislocation: MR findings and surgical implications.