Anterior cruciate ligament mucoid degeneration: selecting the best treatment option. Fourteen knees (48%) had limited flexion, on average 97 degrees. Epub 2021 Nov 24. It results in postoperative laxity, but rarely in frank instability. Disclaimer. mucoid degeneration acl symptoms. An anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the. Typically patients present with knee pain or restricted movement, although often other potential causes for the patient's symptoms are found. Accessibility Does mucoid degeneration of ACL require surgery? - TimesMojo Most authors believe that partial ACL resection is the treatment of choice in symptomatic MD of the ACL. In most cases Physiopedia articles are a secondary source and so should not be used as references. FOIA J Arthrosc Joint Surg 3(1):2833. Initially, partial weightbearing is allowed. They reported that a biopsy indicated mucoid degeneration and a relief of symptoms could be obtained through arthroscopic partial resection of the ligament. MM and A performed the literature search, and data analysis. Several critical distinctions allow a confident diagnosis of an ACL ganglion cyst. Glossary of terms for musculoskeletal radiology. 2020 Jun 2. el Kadi KI, Marcaillou F, Blanc S, Salloum B, Dimontagliari C, Boutayeb F. Mucoid degeneration of the anterior cruciate ligament: a case report. Google Scholar, Chudasama CH, Chudasama VC, Prabhakar MM (2012) Arthroscopic management of mucoid degeneration of anterior cruciate ligament. The https:// ensures that you are connecting to the reported the largest percentage of patients (27.5%) with a positive pivot test. An official website of the United States government. Fig. Complete resection of the ACL without ACL reconstruction is a reliable treatment for symptomatic cases of mucoid degenerated ACL. ACL mucoid degeneration is present on ~10% (range 9-12%) of 3 T MRI examinations and 2% of 1.5 T MRI examinations 6. Ligaments hold our bones together and allow us to bend, twist, pivot and rapidly accelerate and decelerate and yet maintain the stability of our joints. 2022 Apr 11;31:67-71. doi: 10.1016/j.jor.2022.04.004. Average improvement in flexion was 21.5 degrees (0 to 60 degrees). It contrasts with cystic lesions better known as synovial cysts or intercondylar fossa cysts. 2013;15(1). This site needs JavaScript to work properly. Loreto v. Kijakazi, 1:22-CV-1404-JDG | Casetext Search + Citator https://doi.org/10.1046/j.1445-2197.2003.02748.x, Ekhtiari S, Horner NS, Bedi A, Ayeni OR, Khan M. The learning curve for the Latarjet procedure: a systematic review. Sep 2017 - Feb 20186 months. Reeducation. FOIA This is basically an MRI diagnosis of expansion and increased signal of an intact ACL in a person with knee pain which is worse on knee flexion/bending. An official website of the United States government. Association between magnetic resonance imaging characteristics and pathological findings in entire posterior cruciate ligament with mucoid degeneration. Mucoid degeneration of both ACL and PCL. Knee Surg Sports Traumatol Arthrosc. Introduction to Arthroscopic Debridement Arthroscopy 24(6):642649. Finally, partial meniscectomy was commonly performed simultaneously with ACL debridement in all studies, which arguably could be the reason for the postoperative improvement. Ligaments are very tough, fibrous tissue structures. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Conclusions: 2007;90(3):1923. Tissue biopsy was performed in 85% of patients (58 of 68) in the study of Cha et al. -. -Evaluated and planned treatment protocol in accordance with physician. Six studies reported using the pivot shift test; unsurprisingly, Lintz et al. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) flowchart illustrating the selections of trials included in the systematic review. 3. Google Scholar, Cha JR, Lee CC, Cho SD, Youm YS, Jung KH (2013) Symptomatic mucoid degeneration of the anterior cruciate ligament. This is a characteristic appearance of ACL mucoid degeneration where the ACL is expanded and hyperintense but is still continuous with normal alignment. Due to the heterogeneity of data, a meta-analysis was not possible, and a narrative review was deemed most appropriate. Possible etiologies include: It is postulated that mucoid degeneration may be a predisposing factor in the formation of ACL ganglion cysts. Arthroscopic treatment of mucoid hypertrophy of the anterior cruciate ligament. It is lined by the synovial fluid, which provides the nutrition and plays an integral part in healing. -, McIntyre J, Moelleken S, Tirman P. Mucoid degeneration of the anterior cruciate ligament mistaken for ligamentous tears. A total of nine studies were eligible for review. 1992;159(2):35760. Mucoid change | Radiology Reference Article | Radiopaedia.org Kim TH, Lee DH, Lee SH, Kim JM, Kim CW, Bin SI. The aim of this study was to detail the clinical, radiological, arthroscopic, and pathological findings of mucoid degeneration of the anterior cruciate ligament and report the clinical outcomes following arthroscopic treatment. Orthop Traumatol Surg Res 96(4):400406, Bergin D, Morrison WB, Carrino JA, Nallamshetty SN, Bartolozzi AR (2004) Anterior cruciate ligament ganglia and mucoid degeneration: coexistence and clinical correlation. Anterior cruciate ligament mucoid degeneration: a review of the literature and management guidelines. MUCOID DEGENERATION OF ACL - ARTHROSCOPIC TREATMENT - YouTube 1999;81(2):304305. 2023 BioMed Central Ltd unless otherwise stated. Bethesda, MD 20894, Web Policies Part of 2010 Jun;96(4):400-6. doi: 10.1016/j.otsr.2010.02.008. PDF Anterior Cruciate Ligament Ganglion Cyst and Mucoid Degeneration: A Review proposed reduction plasty, which is reduction of the ACL to normal volume without excision of all mucoid tissue. The https:// ensures that you are connecting to the Knee Surg Sports Traumatol Arthrosc. Skeletal Radiol. sharing sensitive information, make sure youre on a federal had the largest number of patients (91) with a mean age of 61 years, which was the oldest study population amongst the nine studies [16]. Score: 4.7/5 (45 votes) . Mucoid degeneration of the ACL is a rare cause of knee pain.1-8) This lesion of the ACL was first reported by Kumar et al.3) in 1999. the degree of laxity, and the patient's age and willingness to pursue vigorous postoperative physical therapy are other major determinants. Accessed 1 Mar 2021. The rate of association between meniscal tears and MDACL ranged from 9 to 96%. Therefore, Anterior Cruciate Ligament tear is more susceptible during any injury to the knee. Mucoid degeneration of the anterior cruciate ligament. Mucinous material within the substance of ACL produces pain and limited motion in the knee. just over two decades ago [], the interest in this condition has quickly gathered pace in the orthopaedic community.Little is known about this condition that affects 1.8-5.3% of the population as per magnetic resonance imaging (MRI) diagnosis [2, 3]. A historical cohort of patients who underwent arthroscopic total or partial excision of the anterior cruciate ligament due to mucoid degeneration between 2011 and 2014 were reviewed. Knee Surg Sports Traumatol Arthrosc 21(3):658663. Patient having mucoid degeneration of ACL seeks multiple orthopedic consultation and most of the time treating orthopedican miss its diagnosis either because of lack of experience or rare cause of pain unless doctor sought magnetic resonance imaging (MRI) of knee. However, MDACL is asymptomatic in most patients. [6], in 62% of patients (18 of 29) in the study of Lintz et al. Effects of pre-operative knee laxity on clinical outcomes after partial anterior cruciate ligament reconstruction. Bergin et al. Epub 2010 May 8. Hide glossary Glossary. Unable to process the form. Only nine studies met our inclusion criteria and they were all case series. Categories were determined in accordance with the study of Ekhtiari et al. The author(s) read and approved the final manuscript. J Chin Med Assoc. Clin Orthop Surg. [16]. Methodological quality of the studies was assessed using the Methodological Index for Non-Randomized Studies (MINORS) criteria [11] (Table1). MDACL is not uncommon, however, it is rarely symptomatic [4, 5]. KoreaMed Synapse Mucoid degeneration,: like degenerative arthritis of a joint, generally occurs as a results of aging. Terms and Conditions, Sweed T, Mussa M, El-Bakoury A, Geutjens G, Metcalfe A. Knee Surg Relat Res. What causes myxoid degeneration? - Shabupc.com We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2009 checklist [9]. [3] and in 1% of patients (3 of 106 knees) in the study of Kim et al. Anterior cruciate ligament mucoid degeneration: selecting the best treatment option. MDACL is differentiated from synovial cysts of the anterior cruciate ligament (ACL) where, in MDACL, mucoid tissue intermingles within ACL fibres and is not contained within a cyst [3]. Postoperative clinical laxity was common, however, symptomatic instability was not. Clinical Outcomes, Return to Sports, and Patient Satisfaction After Anterior Cruciate Ligament Reconstruction in Young and Middle-Aged Patients in an Asian Population-A 2-Year Follow-up Study. With cruciate ligament ganglia, intact ACL fibers can often be visualized coursing through or around the cyst. (A) Bulging of, Fig. as very low (04 points), low (58 points), good (912 points) or excellent (1316 points) [12]. Twenty-eight knees (97%) showed soft and/or delayed stops on postoperative Lachman testing. Mucoid degeneration of ACL. Lintz F, Pujol N, Boisrenoult P, Bargoin K, Beaufils P, Dejour D. Knee Surg Sports Traumatol Arthrosc. Method. Mucoid degeneration of the anterior cruciate ligament (ACL) is a little-known entity. (61years), which was the largest study and represented more than one third of the total patients included in this review. Am J Roentgenol 182(5):12831287. Coronal proton density-weighted magnetic resonance imaging shows a thickening of the anterior cruciate ligament. Please enable it to take advantage of the complete set of features! Radiologic findings associated with mucoid degeneration of the anterior cruciate ligament. The site is secure. Ventura et al. It is a chronic degenerative change of a bulky ACL that may lead to notch impingement syndrome in the absence of instability symptoms and significant trauma history [ 1, 2, 3, 4 ]. Results: This study was registered on PROSPERO [10], an international prospective register of systematic reviews (CRD42018087782). Epidemiology The likelihood of mucoid change within ligaments and tendons increases with age 1. There was strong association between MDACL and chondral lesions (82%) and between MDACL and meniscal tears (69%). The need for delayed ACL reconstruction should be discussed preoperatively, especially if complete resection of the ACL is to be performed. MAUDE Adverse Event Report: GENZYME BIOSURGERY (RIDGEFIELD) SYNVISC ONE Epub 2013 Aug 27. ACL mucoid degeneration is an uncommon pathological condition; the pathogenesis, prevalence, and . There was more than 20% loss to follow up in the study of Kim et al., while the three prospective studies had no loss to follow up [13, 14, 18]. AJR Am J Roentgenol. The mean follow up ranged from 13 to 72months. Arch Orthop Trauma Surg. Anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the anterior cruciate ligament (ACL ). Epub 2018 Jun 13. An official website of the United States government. J Knee Surg. Google Scholar, Lintz F, Pujol N, Boisrenoult P, Bargoin K, Beaufils P, Dejour D (2011) Anterior cruciate ligament mucoid degeneration: a review of the literature and management guidelines. Methods From January 2012 to August 2013, 32 knees (24 females and 8 males with left knee of 14 and 18 of right) were diagnosed with mucoid degeneration of the ACL and underwent arthroscopic treatment, all of whom with a mean age of 58.817.97 years (42-74 years). 2004;182 (5): 1283-7. Patients and methods: Mucoid degeneration (MD) of the anterior cruciate ligament (ACL) is a rare pathological entity with disputed theories of origin. Mucoid degeneration of the patellar ligament in athletes. Mucoid degeneration of the ACL is suspected when an apparently thickened and ill-defined ligament with increased signal intensity on all sequences in MRI is identified in a patient with physically intact ligament and no obvious trauma history. See this image and copyright information in PMC. Mucoid degeneration of ACL Justamom21 Feb 17, 2023 7:27 AM Among other conditions - osteoarthritis, osteopenia, spondylolisthesis- an MRI report showed "severe mucoid degeneration of the ACL" in my left knee. Roberts CC, Towers JD, Spangehl MJ et-al. It is characterized by infiltration of mucoid like substance (glycosaminoglycans) interspersed within the substance of ACL causing knee pain and limited motion. California Privacy Statement, Treatment modalities for ACL ganglion cyst include arthroscopic excision or puncture, CT scan, and ultrasound-guided aspiration [25-26]. Rehabilitation, orthophony, crenotherapy. Bone and joint imaging. The anterior cruciate ligament (ACL) is the most commonly injured of the major knee ligaments. This study concerns complete ACL resec Management of mucoid degeneration of the anterior cruciate ligament: a systematic review. 2018. http://journals.sagepub.com/doi/10.1177/2325967118786930, Pandey V, Suman C, Sharma S, Rao SP, Kiran Acharya K, Sambaji C (2014) Mucoid degeneration of the anterior cruciate ligament: management and outcome. Noninfiltrating synovial cysts of the ACL were excluded. Mucoid degeneration of the anterior cruciate ligament: a case report. Introduction Mucoid degeneration of the anterior cruciate ligament (MDACL) is a rare entity, first described by Kumar et al. There was strong association between degenerative changes and MDACL (82% having chondral and 69% meniscal lesions), which might suggest that MDACL is a degenerative process. "Traumatic theory - post injury, ACL fibroblasts secrete glycosaminoglycans, the mucin substance within the ACL. Anterior cruciate ligament mucoid degeneration - Radiopaedia JBR-BTR. Outcome of Arthroscopic Treatment of Mucoid Degeneration of the Anterior Cruciate Ligament. 2011 Aug;19(8):1326-33. doi: 10.1007/s00167-011-1433-0. 8600 Rockville Pike The ACL appears on MRI to be enlarged with cystic changes throughout, however it is intact. A long duration of non-specific knee pain in a patient should be evaluated with MRI. Diffuse Intrasubstance Signal Abnormalities Ofthe Posterior Cruciate That is usually the journal article where the information was first stated. 2004;182(5):12837. 2001;17(9):E37. Lintz F, Pujol N, Boisrenoult P, Bargoin K, Beaufils P, Dejour D. Knee Surg Sports Traumatol Arthrosc. After the literature search and exclusion of duplicates, 54 papers were retrieved: 12 articles were assessed for eligibility, and of these, 9 papers met the inclusion criteria and were included in the systematic review [3, 6, 13,14,15,16,17,18,19] (Fig. Patients will . Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-3615, Case 11: with Hoffa fat pad ganglion cyst, Case 12: tibial nerve schwannoma and ACL mucoid degeneration, Case 1: Complete ACL tear and meniscal tears, Case 2: Anomalous insertion of the medial meniscus, View Frank Gaillard's current disclosures, see full revision history and disclosures, anterior cruciate ligament ganglion cysts, 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, Mucoid degeneration of the anterior cruciate ligament, congenital or acquired synovial tissue entrapment between ACL fibers. Management of mucoid degeneration of the anterior cruciate ligament: a systematic review. Ventura D, Nuez JH, Joshi-Jubert N, Castellet E, Minguell J. Clin Orthop Surg. Mucoid cystic degeneration of the cruciate ligament. Preoperative magnetic resonance imaging (MRI), Fig. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. W B Saunders Co. (2005) ISBN:0721602703. statement and Reeducation. Epub 2011 Feb 18. Cho SD, Youm YS, Lee CC et-al. https://doi.org/10.4055/cios.2018.10.3.307, University Hospitals of Derby and Burton, Uttoxeter Rd, Derby, DE22 3NE, UK, Trauma and Orthopaedic Speciality Trainee, West Midlands Deanery, Birmingham Rotation, Birmingham, UK, University Hospitals Plymouth NHS Trust, Plymouth, UK, University of Alexandria, Alexandria, Egypt, University Hospital Coventry and Warwickshire, Clifford Bridge Road, Walsgrave, Coventry, CV2 2DX, UK, You can also search for this author in 2009 Jul;17(7):737-40. doi: 10.1007/s00167-008-0690-z. We herein describe a case of PCL mucoid degeneration presented with secondary ACL . 2021 Sep;50(9):1837-1843. doi: 10.1007/s00256-021-03750-7. Patients in all studies presented with central or posterior knee pain, mainly with terminal extension in three studies [14, 16, 17]. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. It often presents with progressive knee pain, restriction in range of motion without a significant history of trauma, and without knee instability. The main MRI finding of ACL mucoid degeneration is a celery stalk appearance [26, 27]. Knee Surg & Relat Res 33, 26 (2021). in 1999 [ 1 ]. Would you like email updates of new search results? This site needs JavaScript to work properly. proposed a different intervention called reduction plasty, whereby the hypertrophic ACL is reduced to normal size without excision of all mucoid substance [17]. It results in postoperative laxity, but rarely in frank instability. official website and that any information you provide is encrypted Mucoid degeneration (MD) of the anterior cruciate ligament (ACL) is a benign knee pathology, which is often indicated for surgical treatment if symptomatic. National Library of Medicine 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. CIOS :: Clinics in Orthopedic Surgery https://doi.org/10.1007/s002560100336, Narvekar A, Gajjar S (2004) Mucoid degeneration of the anterior cruciate ligament. Here are the search results of the thread mucoid degeneration of acl treatment from Bing. Four studies reported only postoperative scores, which were comparable to those in other studies. AJR Am J Roentgenol. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). We report a case of mucoid degeneration of the anterior cruciate ligament (ACL). Arthroscopic debridement may help relieve the anterior knee pain. In the Lintz study, total resection of the ACL was performed in 17 out of 29 knees, while in the Ventura study total resection was performed in 17 out of 25 patients. 2 ). Twenty knees (69%) had associated cartilaginous lesions and 19 (66%) had meniscal lesions. At the time the article was last revised Dai Roberts had no recorded disclosures. 8600 Rockville Pike Mucoid degeneration of the ACL is suspected when an apparently thickened and ill-defined ligament with increased signal intensity on all sequences in MRI is identified in a patient with physically intact ligament and no obvious trauma history. https://doi.org/10.1016/j.arthro.2008.02.004, Morice A, Coupry A, Lintz F, Robert H (2013) Reduction plasty for hypertrophic anterior cruciate ligament mucoid degeneration: clinical and knee laxity outcomes in 23 cases. Pre-debridement arthroscopic view showing yellowish content in the anterior cruciate ligament. This study concerns complete ACL resection as a treatment of mucoid degenerated ACL. 2. Rajani AM, Shah UA, Mittal ARS, Gupta S, Garg R, Punamiya M. Knee Surg Relat Res. Google Scholar, Salvati F, Rossi F, Limbucci N, Pistoia ML, Barile A, Masciocchi C (2008) Mucoid metaplastic-degeneration of anterior cruciate ligament. The cause is not really known, but patients usually do not complain of instability. The pathogenesis remains controversial. Magn Reson Imaging Clin N Am. Imaging: Plain radiographs There is strong association between MDACL and chondral and meniscal lesions, which may support the theory that MDACL is a degenerative process. Mucoid degeneration of A C L is more common and literature has also reported many cases, but for PCL only few cases have been reported in English literature. Knee Surgery & Related Research Loss to follow up was not mentioned in the other five studies [3, 6, 15, 17, 19]. PubMed Central Individuals with mucoid degeneration of the ACL were excluded. A September 2018 MRI of the left knee showed anterior cruciate ligament and mucoid degeneration with intra cruciate ganglion . Does Femoral Intercondylar Notch Volume Differ in Anterior Cruciate Ligament-Injured Adult Patients Compared to the Uninjured? This was lowest in the study of Cha et al. HHS Vulnerability Disclosure, Help 1. National Library of Medicine sharing sensitive information, make sure youre on a federal Before On MRI, the ligament is thickened and ill-defined with a "celery stalk" appearance. -Provided skilled hands on in post-op rehabilitation to various population including Head and neck cancers, Lymph edema management, Bone cancers. Unauthorized use of these marks is strictly prohibited. Bookshelf Springer Nature. Introduction Mucoid degeneration of the anterior cruciate ligament (ACL) is a little-known pathology. sharing sensitive information, make sure youre on a federal Answer (1 of 2): Most of the time mucoid degenrative changes in the ACL does not cause any problemonly if u have sign of ACL instability or the bending of the knee is reduced you may need a arthroscopic evaluation usually u may skip without ACL reconstruction but some of us will need AcL recons. HHS Vulnerability Disclosure, Help Introduction: and Ventura et al. All rights reserved. Several authors have identified this condition, described their experiences, and suggested their own guidelines for management. Arthroscopic treatment may include ACL resection, which raises the questions about the harmlessness of this procedure and the risk of anterior instability. This site needs JavaScript to work properly. CAS Association between magnetic resonance imaging characteristics and pathological findings in entire posterior cruciate ligament with mucoid degeneration. Background: Mucoid degeneration of the anterior cruciate ligament (ACL) is an uncommon non-traumatic cause of knee pain and motion restriction, typically seen in a middle-aged population. Postoperative symptomatic instability was not common in eight studies, but was observed in 48% of patients in the study of Lintz et al., with two patients having a delayed ACL reconstruction. Mucoid degeneration of the anterior cruciate ligament: can platelet ADVERTISEMENT: Supporters see fewer/no ads. [PDF] Mucoid degeneration of the anterior cruciate Ligament: a case . Mucoid Degeneration of the Anterior Cruciate Ligament - ResearchGate The retrospective study by Kim et al. Symptomatic ACL mucoid degeneration in middle-age athletes. Coronal T2 weighted fat suppressed fast spin echo image showed complex anterior cruciate ligament ganglion cyst arising from superior aspect of ligament. At last follow-up, the mean visual analogue scale score, International Knee Documentation Committee score, and Tegner Lysholm Knee score improved (p < 0.01). Mucoid degeneration of the anterior cruciate ligament (ACL) is a rare cause of knee pain. The anterior cruciate ligament (ACL) is one of the more vital and more easily injured ligaments within our knee. 2018 Sep;10(3):307-314. doi: 10.4055/cios.2018.10.3.307. Furthermore, this raises the question as to whether the symptoms (pain and diminished range of movement) were solely due to MDACL and not secondary to other associated pathological conditions. Level of evidence: J Bone Joint Surg Ser B 81(2):304305. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Mucoid degeneration of the anterior cruciate ligament (ACL) is a very rare cause of knee pain. Postoperative ACL laxity is a common finding after ACL arthroscopic debridement, however, symptomatic instability is not. PMC HHS Vulnerability Disclosure, Help The site is secure. This ranged from 90 to 95% in all studies, except in the report by Kim et al., where only 53.8% of patients (57/106) had complete pain relief after surgery. . Unauthorized use of these marks is strictly prohibited. All patients (100%, n=11) reported a good to very good surgery satisfaction. The .gov means its official. However, young patients should be forewarned about the risk of instability, and an anterior cruciate ligament reconstruction could be necessary. Epub 2021 Mar 8. The rate of simultaneous meniscectomy ranged from 13 to 44%. Mucoid degeneration of the anterior cruciate ligament 8600 Rockville Pike Seventeen females (67%) and eight males (33%) were included in the final analysis. Anterior cruciate ligament mucoid degeneration: a review of the literature and management guidelines. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If arthroscopy is performed, the ligament may appear entirely normal, especially using the standard anterior portal approach. Int J Curr Res Aca Rev 4(11):1824 http://www.ijcrar.com/abstractview.php?ID=228&vol=4-11-2016&SNo=3, Kim TH, Lee DH, Lee SH, Kim JM, Kim CW, Bin SI (2008) Arthroscopic treatment of mucoid hypertrophy of the anterior cruciate ligament.