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The impact of body mass index on the accuracy of the physical examination of the knee

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Abstract

Purpose

Obesity is a worldwide pandemic; however, no adaptations were made to the physical examination of obese patient’s knees. The accuracy of the physical examination is critical for correct assessment and selection of treatment. We aimed to assess whether body mass index (BMI) affects the sensitivity and specificity of common provocative knee tests.

Methods

We studied 210 patients who underwent knee arthroscopy to treat anterior cruciate ligament (ACL) and meniscal pathologies. BMI and the knee’s physical examination were documented pre-operatively. Sensitivity, specificity, and accuracy of ACL and meniscal provocative tests in relation to BMI were evaluated using arthroscopy as a gold standard.

Results

The Anterior Drawer, Lachman, and Pivot-Shift tests for ACL tears were significantly less accurate and sensitive, yet more specific, in obese patients when compared to normal and overweight patients. The McMurray, Apley Grind, and Thessaly tests for medial meniscus tears showed greater sensitivity, but lower specificity, in patients with increased BMI. Above normal BMIs, independently of age and gender, were significantly associated with higher odds for positive ACL tests.

Conclusion

Tests for ACL tears are less sensitive in obese patients and alternatives to the classic tests should be considered. Medial meniscus tests tend to be more sensitive and less specific in patients with greater BMIs. Their results should be carefully interpreted due to possible false positives. The physician should take into consideration the impact of patient BMI on the accuracy of their physical examination of the knee to optimize treatment decision-making.

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Data availability

The authors declare data is available per request.

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Authors and Affiliations

  1. Department of Orthopaedic Surgery, Shamir Medical Center and Tel Aviv University, Tel Aviv, Israel

    Ron Gilat, Ilan Y. Mitchnik, Assaf Moriah, Almog Levi, Ornit Cohen, Dror Lindner, Yiftah Beer & Gabriel Agar

Authors
  1. Ron Gilat
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  2. Ilan Y. Mitchnik
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  3. Assaf Moriah
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  4. Almog Levi
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  5. Ornit Cohen
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  6. Dror Lindner
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  7. Yiftah Beer
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  8. Gabriel Agar
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Contributions

RG conceived the study, designed and coordinated it, received institutional board approval, collected materials, and drafted the manuscript. IM carried out the statistical analysis, drafted the manuscript, reported the results, discussed their interpretation, and designed the tables and illustrations. AM collected data and drafted the original manuscript. AL collected data and drafted the original manuscript. OC carried out the statistical analysis and edited and reviewed the final version. DL assisted in study design and editing and review of the manuscript. YB assisted in study conception and supervision, edited and reviewed the final version. AG assisted in study conception and supervision, edited and reviewed the final version.

Corresponding author

Correspondence to Ron Gilat.

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Ethical approval

Institutional review board approval was obtained prior to study initiation.

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Informed consent was not required for this study as per institutional review board approval.

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Informed consent was not required for this study as per institutional review board approval.

Conflict of interest

The authors declare no competing interests.

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Gilat, R., Mitchnik, I.Y., Moriah, A. et al. The impact of body mass index on the accuracy of the physical examination of the knee. International Orthopaedics (SICOT) 46, 831–836 (2022). https://doi.org/10.1007/s00264-021-05277-x

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  • DOI: https://doi.org/10.1007/s00264-021-05277-x

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