Visual inspection for lower limb malalignment diagnosis is unreliable

Key Points

1. Visual inspection of lower limb alignment is a common practice in musculoskeletal care for various pathologies including, but not limited to, knee pain, hip pain, ankle pain, and low back pain.
2. The reliability of visual inspection (visual observation of the patient in stance on both legs in the examination room) for the detection of lower limb malalignment is currently unknown.
3. The findings of this study demonstrate that when compared to the gold standard of whole leg radiography, visual inspection of lower limb alignment is not valid or reliable.

BACKGROUND & OBJECTIVE

It has previously been established that varus malalignment of the knee is present in 53% to 76% of individuals with unicompartmental knee osteoarthritis (OA) (1). Currently, this malalignment is thought to increase the risk of both the development and progression of OA due to loading imbalance of the knee joint (2,3).

During physical examination, several methods are available for the assessment of lower limb alignment (4,5). All these alternatives for whole leg radiographs (WLRs) have been tested and compared with the measured leg axis on WLRs for correlations with results ranging from low, moderate to good. In the case of suspected malalignment, physicians often choose to obtain additional WLR which exposes patients to unnecessary radiation and increases health care costs.

This study aimed to investigate how reliable visual inspections are in terms of detecting lower limb malalignments without the addition of tools and other physical examinations. The authors’ hypothesis was that only a visual inspection of the lower limb is not sufficient for the detection of lower limb malalignment.

Varus malalignment of the knee is present in 53% to 76% of individuals with unicompartmental knee osteoarthritis.

The overdiagnosis of normal anatomic presentation as pathological or dysfunctional has the underlying potential for long ranging iatrogenic effects.

METHODS

• For this study, patients were recruited at the outpatient clinic of the University Medical Center (UMC) Utrecht.

• Patients were eligible when a WLR was obtained on the same day as their appointment at the outpatient clinic.

• Exclusion criteria were age below 18 years; inability to read, communicate, and/or speak the Dutch language; and incapable of providing informed consent.

• When a patient was referred for WLR, a digital photo was also taken for visual inspection of the lower extremity. The conditions for obtaining the digital photograph were kept similar to the WLR with the patient’s feet placed 10° externally rotated and 10 cm apart on a template, knees in full extension, and both arms alongside the body.

• Each digital photograph was randomly assessed twice bilaterally by 4 observers with 1 week in-between, with varying experience levels (orthopedic surgeon with 10 years’ experience, orthopedic surgeon with 5 years’ experience, orthopedic resident, and researcher).

• All observers were blinded from the hip knee angle (HKA) present on WLRs during visual observations. HKA alignment was divided into four categories:

  • Severe valgus (>5°)
  • Moderate valgus (3°-5°)
  • Neutral
  • Moderate varus (3°-5°)
  • Severe varus (>5°)

RESULTS

• Radiographic assessment of the 100 included legs resulted in 11 severe varus, 16 moderate varus, 67 neutral, 6 moderate valgus, and 0 severe valgus (based on the HKA measured on the WLR) cases.

• When radiographic assessment was compared with visual inspections, the percentage of incorrect visual leg axis assessments ranged between 45.8% and 75.0%. The errors were lowest in patients with a moderate valgus alignment and highest when the patient presented a severe varus deformity.

• No significant difference was noted between the accuracy of more and less experienced examiners. Patients with a neutral leg alignment were assessed to be pathological in 50.7% of cases.

• Women had an increased odds ratio of 3.7 (P = 0.001) for incorrect visual leg alignment assessment. Also, an increasing HKA itself had a significant (P = 0.003) effect on incorrect visual assessments with an odds ratio of 1.4.

LIMITATIONS

• The authors of this study detailed no limitations to the study, which may be perceived as a limitation.

• Limitations noted by the reviewer include the lack of multicenter design for patient selection and a design in which all examiners practiced in the same center for knee pathology. These two factors taken together may create measurements with an inherent clinical bias specific to the clinicians in this center.

• Additionally, the standardization of standing position was placed in the research design to limit variability and achieve consistency. However, anatomical variance exists between human beings and the assessment may have yielded different results if patients were allowed to assume their natural and comfortable standing posture.

CLINICAL IMPLICATIONS

The results of this study provide evidence that the clinical utilization of visual limb inspection for lower extremity alignment has poor interrater reliability and validity when compared to WLR’s. These findings should be integrated into current clinical practice in order to update biomechanical and postural narratives consistently utilized in clinical decision-making models for injury risk assessment, lower extremity dysfunction, and lumbar spine pathology.

The results of this study also demonstrated that gender influences the visual assessment of patients’ leg axis. It is important to note that women appear to present at an increased risk for incorrect visual ratings. A possible explanation for this could be the difference in the anatomical axis of the femur between men and women. Understanding the influence of gender on examiner perception of lower limb alignment should be considered when evaluating patients clinically.

Interestingly, no significant difference was noted between the accuracy of more and less experienced examiners demonstrating that ability to assess lower limb alignment does not improve with practice and repetition through one’s career. Among the most concerning findings was that patients with a neutral leg alignment were assessed to be pathological in 50.7% of the time. The overdiagnosis of normal anatomic presentation as pathological or dysfunctional has the underlying potential for long ranging iatrogenic effects, including but not limited to, unnecessary intervention, erroneous treatment plans, and associated health care cost to patients.

+STUDY REFERENCE

Nguyen H, van Egmond N, de Visser H, Weinans H, Sakkers R, Custers R (2022) Visual inspection for lower limb malalignment diagnosis is unreliable. Cartilage, 13(4), 59-65.

SUPPORTING REFERENCE

1. Hinman RS, May RL, Crossley KM. Is there an alternative to the full-leg radiograph for determining knee joint alignment in osteoarthritis? Arthritis Care Res. 2006;55(2):306-13.
2. Palmer JS, Jones LD, Monk AP, Nevitt M, Lynch J, Beard DJ, et al. Varus alignment of the proximal tibia is associated with structural progression in early to moderate varus osteoarthritis of the knee. Knee Surg Sports Traumatol Arthrosc. 2020;28(10):3279-86.
3. Glyn-Jones S, Palmer AJR, Agricola R, Price AJ, Vincent TL, Weinans H, et al. Osteoarthritis. Lancet. 2015;386(9991):376-87.
4. Navali AM, Bahari LAS, Nazari B. A comparative assessment of alternatives to the full-leg radiograph for determining knee joint alignment. Sport Med Arthrosc Rehabil Ther Technol. 2012;4(1):1-7. Kraus VB, Vail TP, Worrell T, McDaniel G. A comparative assessment of alignment angle of the knee by radiographic and physical examination methods. Arthritis Rheum. 2005;52(6):1730-5.
5. Kraus VB, Vail TP, Worrell T, McDaniel G. A comparative assessment of alignment angle of the knee by radiographic and physical examination methods. Arthritis Rheum. 2005;52(6):1730-5.