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Clinical and epidemiological research
Extended report
Breaking the Law of Valgus: the surprising and unexplained prevalence of medial patellofemoral cartilage damage
  1. K Douglas Gross1,2,
  2. Jingbo Niu1,
  3. Joshua J Stefanik1,
  4. Ali Guermazi3,
  5. Frank W Roemer3,
  6. Leena Sharma4,
  7. Michael C Nevitt5,
  8. Neil A Segal6,
  9. Cora E Lewis7,
  10. David T Felson1
  1. 1Clinical Epidemiology Research and Training Unit, Boston University School of Medicine, Boston, Massachusetts, USA
  2. 2Department of Physical Therapy, MGH Institute of Health Professions, Boston, Massachusetts, USA
  3. 3Department of Radiology, Boston University School of Medicine, Boston, Massachusetts, USA
  4. 4Department of Internal Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
  5. 5Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA
  6. 6Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA
  7. 7Department of Preventive Medicine, University of Alabama, Birmingham, Alabama, USA
  1. Correspondence to K Douglas Gross, Boston University School of Medicine, Clinical Epidemiology Research and Training Unit, 650 Albany Street, Suite X-200, Boston, Massachusetts 02118, USA; grossd{at}bu.edu

Abstract

Objectives To compare the prevalence of medial and lateral patellofemoral (PF) cartilage damage in three large osteoarthritis (OA) studies and determine the relationship of this damage to varus, neutral and valgus knee alignment.

Methods In the Boston OA of the Knee, Framingham OA and Multicenter OA studies, MRIs were read for cartilage morphology at the medial and lateral patella and trochlea femoris using Whole-Organ MRI Scores (WORMS). WORMS scores ≥2 (any cartilage defect), ≥3 (areas of partial thickness loss), ≥4 (diffuse partial thickness loss) and ≥5 (extensive full thickness loss) were all variously considered as thresholds to identify damage that may indicate OA. Full-limb radiographs were measured for mechanical alignment, and varus (<−2°), neutral (-2° to 2°) and valgus (>2°) knees were identified.

Results The prevalence of medial PF cartilage damage exceeded that of lateral damage in all three studies and according to nearly every threshold. Only among severely involved knees (WORMS ≥4 or ≥5) did the prevalence of lateral PF cartilage damage approximate that of medial damage. The high prevalence of medial PF damage persisted in all strata of knee alignment. Even among knees with valgus alignment, the prevalence of lateral PF cartilage damage equalled or surpassed that of medial PF damage only when the threshold was specific to severely involved knees.

Conclusions Medial PF cartilage damage is at least as prevalent within these older adult populations as lateral PF cartilage damage.

https://doi.org/10.1136/annrheumdis-2011-200606

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    Footnotes

    • Funding Provided by the National Institutes of Health.

    • Competing interests Dr Guermazi has received consultancy fees (more than $10 000 each) from Stryker and Novartis, and (less than $10 000 each) from Merck Serono, Facet Solutions and Genzyme. He owns stock and/or holds stock options in Synarc and is president of Boston Imaging Core Lab, LLC. Dr Guermazi was compensated for MRI readings that he performed as part of this study. Dr Roemer owns stock and/or holds stock options in Boston Imaging Core Lab, LLC. Dr Roemer was compensated for MRI readings that he performed as part of this study.

    • Patient consent Obtained.

    • Ethics approval This study was conducted with the approval of the Boston University Medical Center Institutional Review Board.

    • Provenance and peer review Not commissioned; externally peer reviewed