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Scientific Articles   |    
Reliability of Clinical Findings and Magnetic Resonance Imaging for the Diagnosis of Chondromalacia Patellae
Harri K. Pihlajamäki, MD, PhD1; Paavo-Ilari Kuikka, MD1; Vesa-Veikko Leppänen, MD1; Martti J. Kiuru, MD, PhD1; Ville M. Mattila, MD, PhD1
1 Research Unit, Centre for Military Medicine, P.O. Box 50, FIN-00301 Helsinki, Finland. E-mail address for H.K. Pihlajamäki: Harri.Pihlajamaki@helsinki.fi
View Disclosures and Other Information
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at the Centre for Military Medicine and the Department of Orthopaedic Surgery, Central Military Hospital, Helsinki, Finland

Copyright ©2010 American Society for Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Apr 01;92(4):927-934. doi: 10.2106/JBJS.H.01527
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Abstract

Background: 

This diagnostic study was performed to determine the correlation between anterior knee pain and chondromalacia patellae and to define the reliability of magnetic resonance imaging for the diagnosis of chondromalacia patellae.

Methods: 

Fifty-six young adults (median age, 19.5 years) with anterior knee pain had magnetic resonance imaging of the knee followed by arthroscopy. The patellar chondral lesions identified by magnetic resonance imaging were compared with the arthroscopic findings.

Results: 

Arthroscopy confirmed the presence of chondromalacia patellae in twenty-five (45%) of the fifty-six knees, a synovial plica in twenty-five knees, a meniscal tear in four knees, and a femorotibial chondral lesion in four knees; normal anatomy was seen in six knees. No association was found between the severity of the chondromalacia patellae seen at arthroscopy and the clinical symptoms of anterior knee pain syndrome (p = 0.83). The positive predictive value for the ability of 1.0-T magnetic resonance imaging to detect chondromalacia patellae was 75% (95% confidence interval, 53% to 89%), the negative predictive value was 72% (95% confidence interval, 56% to 84%), the sensitivity was 60% (95% confidence interval, 41% to 77%), the specificity was 84% (95% confidence interval, 67% to 93%), and the diagnostic accuracy was 73% (95% confidence interval, 60% to 83%). The sensitivity was 13% (95% confidence interval, 2% to 49%) for grade-I lesions and 83% (95% confidence interval, 59% to 94%) for grade-II, III, or IV lesions.

Conclusions: 

Chondromalacia patellae cannot be diagnosed on the basis of symptoms or with current physical examination methods. The present study demonstrated no correlation between the severity of chondromalacia patellae and the clinical symptoms of anterior knee pain syndrome. Thus, symptoms of anterior knee pain syndrome should not be used as an indication for knee arthroscopy. The sensitivity of 1.0-T magnetic resonance imaging was low for grade-I lesions but considerably higher for more severe (grade-II, III, or IV) lesions. Magnetic resonance imaging may be considered an accurate diagnostic tool for identification of more severe cases of chondromalacia patellae.

Level of Evidence: 

Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence.

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    References

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Harri K. Pihlajamäki, MD, PhD
    Posted on July 06, 2010
    Dr. Pihlajamäki and colleagues respond to Drs. Torres-Gomez and Falcon
    Centre for Military Medicine, Helsinki, Finland

    Thank you for your interest in our article. We appreciate your clarification of these often misused statistical terms. Thank you also for calculating the positive and negative likelihood ratios. We are familiar with these statistical terms and agree that the word "reliability" was not used in its strict statistical sense, as you kindly pointed out. However, we believe that the original article is understandable to the readers and also four reviewers and the editorial office accepted the terms as they were used. Thus, the statistical terms you mention tend to be used more liberally, even in scientific articles. We do appreciate your pointing out the correct statistical meaning of these terms and agree that this is an important issue.

    Armando Torres-Gomez
    Posted on June 08, 2010
    Reliability, Validity, and Other Scientific Terms
    ABC Medical Center, Mexico City, Mexico

    To the Editor:

    We found the paper by Pihlajamäki et al. (1) interesting although the title does not relate in any manner to the body of the article. My attention was drawn to a paper on the “reliability” of the MRI for the diagnosis of chondromalacia patellae. What I found, however, was a research on the “validity” of the issue. Reliability (or precision) is the degree in which results (of a measurement instrument such as the MRI) are reproduced in repeated measurements in similar conditions. Validity is the degree in which an instrument measures what it was designed to measure.

    Reliability can be assessed in multiple manners and the most used in medical sciences are. 1. Intraclass correlation coefficients, 2. Cohen`s Kappa statistic and 3. Interclass correlations (Pearson or Spearman). The reliability coefficient can be interpreted as the interrater and interrater reliability (depending on the study design). An instrument that is reliable can be valid, but a non-reliable instrument hardly will be valid.

    Validity can be assessed in multiple ways. The appraisal of the validity of a test is a complex task. However, for diagnostic instruments with dichotomic outcomes (disease/non-disease), the evaluation of validity gets less complicated. The report of the sensitivity, specificity, predictive values and test precision give an account for the validity of the diagnostic instrument. This paper deals with the “validity” of the MRI, not with its “reliability”. Moreover, some important data is missing: the positive and negative likelihood ratios (positive likelihood ratio in this paper was 3.75, the negative likelihood ratio was 0.476). These ratios reflect the likelihood of a patient with a positive test of having the disease and the likelihood of a patient with a negative test of not having it.

    Finally, the summary states that “This diagnostic study was performed to determine the correlation between anterior knee pain and chondromalacia patellae”. The study does not “correlate”, but “associates” the findings of the MRI with the outcomes of the arthroscopy.

    The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

    Reference

    1. Pihlajamäki HK, Kuikka PI, Leppänen VV, Kiuru MJ, Mattila VM. Reliability of clinical findings and magnetic resonance imaging for the diagnosis of chondromalacia patellae. J Bone Joint Surg Am. 2010;92:927-34.

    Harri K. Pihlajamäki, MD, PhD
    Posted on May 20, 2010
    Dr. Pihlajamäki and colleagues respond to Dr. Manes
    Centre for Military Medicine, Helsinki, Finland

    Thank you for your interest in our manuscript. Traditionally, the diagnosis of chondromalacia patellae has been based on the presenting symptoms and physical examination by an orthopedic surgeon. Based on the current consensus of the International Patellofemoral Study Group, however, the term "chondromalacia patellae" should be used only when discussing arthroscopic findings of softened patellar articular cartilage (1-2). The term "anterior knee pain" should be used to describe symptoms of pain, presence of grating, pain after prolonged sitting or squatting, crepitation with knee movement, and tenderness of the patella.

    In past decades, the pathophysiology of anterior knee pain has been attributed to chondromalacia patellae and patellofemoral malalignment. Current opinion, however, is that chondromalacia patellae is not directly related to symptoms of anterior knee pain (3-4). Patellofemoral malalignment still seems to be a risk factor for anterior knee pain, but it is not sufficient to cause anterior knee pain alone and the onset of pain requires additional provoking factors (5).

    The tissue homeostasis theory by Scott F. Dye (6) has become more popular as an explanation for anterior knee pain. According to Dye, loss of tissue homeostasis causes anterior knee pain when loading of the knee joint exceeds its envelope of function. This can happen when the normal knee is simply overloaded or when other physiopathologic factors are present, such as an inflamed synovial lining or increased osseous metabolic activity of the patella, which decrease the amount of loading that a knee can normally withstand. The primary finding in our study was that clinical examination and symptoms previously suggested to be related to chondromalacia patellae (that is, the symptoms described by Dr. Manes in his letter) were not related to the arthroscopic findings of chondromalacia patellae. Our aim was not to promote unnecessary tests, including MRI scans.

    Diagnosis of anterior knee pain can still be made based on symptoms and careful physical examination.

    References

    1. Grelsamer RP. Patellofemoral semantics. The Tower of Babel. The International Patellofemoral Study Group. Am J Knee Surg. 1997;10:92-5.

    2. Sanchis-Alfonso V, editor. Anterior knee pain and patellar instability. London: Springer; 2006. p 381.

    3. Leslie IJ, Bentley G. Arthroscopy in the diagnosis of chondromalacia patellae. Ann Rheum Dis. 1978;37:540-7.

    4. Pihlajamäki HK, Kuikka PI, Leppänen VV, Kiuru MJ, Mattila VM. Reliability of clinical findings and magnetic resonance imaging for the diagnosis of chondromalacia patellae. J Bone Joint Surg Am. 2010;92:927-34.

    5. Grelsamer RP. Patellar malalignment. J Bone Joint Surg Am. 2000;82:1639-50.

    6. Dye SF. The pathophysiology of patellofemoral pain: a tissue homeostasis perspective. Clin Orthop Relat Res. 2005;436:100-10.

    Harvey Manes
    Posted on April 09, 2010
    Re: Chondromalacia Patella-MRI Versus History & Physical
    NULL

    To the Editor:

    I am not sure I agree with the conclusion of this article—"chondromalacia of the patella cannot be diagnosed based on symptoms or with current methods of physical exam". I still depend on the History—1) level of pain 1-10, 2) presence of grating, catching, locking, giving way, 3) increase pain on prolonged sitting, squatting etc., and Physical Exam—1) degree of crepitation on AROM and PROM, 2) manual pressure test while patient contracts quads, 3) tenderness on underside of patella 4) AROM against resistance is painful. The actual photo (Figure 2A) of a large grade III lesion is so subtle that many radiologists and orthopaedic surgeons could completely miss the diagnosis. The implied suggestion that in order to make a diagnosis of patella chondromalacia one must obtain an MRI, will result in many unnecessary tests.

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

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