Bow Legged Or Knocked Knees? Or Normal?

Different knee shapes

Visual inspection of lower limb alignment is common standard practice for us in our clinics (and elsewhere I am sure) when a patient comes in with ankle, knee, hip and low back pain.

You would think that as a trained health professional, we would be able to see if a person has normal, bow legs (varus) or knocked knees (valgus) quite easily. If it was an extreme valgus or varus it would be fairly easy to differentiate. What if you saw the following pictures below?

Varus or valgus?

How about this? Confused?

Hence I was rather surprised when a published study (Nguyen et al, 2022) found that visual inspection of lower limb alignment is not valid nor reliable when compared to the gold standard of whole leg radiography (WLR).

The study involved 50 patients who underwent a WLR and a standardized digital photograph of the lower limbs (pictured below). The patient's feet were placed 10 cm apart and in 10 degrees of external rotation with knees in full extension and both arms alongside the body. Pictures were taken from knee height, 2 meters away from the patient. 

WLR and digital photograph

There were 4 assessors who rated the digital photograph twice. Two are orthopaedic surgeons with 10 and 5 years experience respectively. The remaining two were an orthopaedic resident and a researcher. They were unaware of the patients' hip knee angle (HKA).

Knees were rated with severe valgus (>5 degrees), moderate valgus (2-5 degrees), neutral, moderate varus (2-5 degrees) and severe varus (>5 degrees).

Ready for the results? The percentage of incorrect visual leg assessments ranged between 46-75 percent. Now that's high! The errors were lowest in patients with moderate valgus alignment (knock knees) and highest when the patient presented with a severe varus deformity (bow legs). See the picture below of a patient I saw recently. How can the error be highest when it is bow legged? Isn't that fairly obvious?

Surely this varus is obvious

There were patients with a neutral leg alignment but were assessed to be pathological in 50.7 percent of cases. I am concerned about this since the wrong diagnosis of normal presentation as pathological/ dysfunctional may potentially cause the patient to opt for surgical intervention. This will lead to increased health care cost for patients and insurers.

Interestingly, there were no significant differences between the accuracy of more experienced verus less experienced assessors.You would think that the ability to assess alignment would improve with practice through one's working life.

The results also show that there were gender influences. Women do present an increased risk for incorrect readings due to the difference in the angle of the thigh bone between men and women.

The authors concluded that visual assessment of lower limb alignment does not provide clinically relevant information. Physical examinations and X-ray assessments are advised.

Limitations for this study? My biggest gripe was that visual assessments were done on 2-dimensional (2D) digital photographs instead of in person assessment. It is definitely easier (and more accurate) to visually assess a patient than to look at a digital photograph. Only 1 assessor measured the HKA on the WLRs, so there is no comparison for inter-assessor reliability.

Hopefully our surgeons here in Singapore are better are visually assessing patients. They should also do whole leg x-rays and in clinic assessments. Make sure yours does.

We see many of these cases. Come see us in our clinics if you have any pain or discomfort. While we cannot alter the shape of your knees, we can definitely reduce or take away the symptoms.

Reference

Nguyen HC, Egmond N, De Visser HM et al (2022). Visual Inspection For Lower Limb Malalignment Diagnosis Is Unreliable. Cartilage. 13(4): 59-65. DOI: 10.1177/19476035221113952