Hip-knee-ankle angle

Last revised by Henry Knipe on 2 Apr 2021

Citation, DOI, disclosures and article data

Citation:

Weng N, Knipe H, Rock P, Hip-knee-ankle angle. Reference article, Radiopaedia.org (Accessed on 18 Apr 2024) https://doi.org/10.53347/rID-88254

DOI:

https://doi.org/10.53347/rID-88254

Permalink:

https://radiopaedia.org/articles/88254

rID:

88254

Article created:

1 Apr 2021, Nicholas Weng

Disclosures:

At the time the article was created Nicholas Weng had no recorded disclosures.

View Nicholas Weng's current disclosures

Last revised:

2 Apr 2021, Henry Knipe ◉ ◈

Disclosures:

At the time the article was last revised Henry Knipe had no recorded disclosures.

View Henry Knipe's current disclosures

Revisions:

4 times, by 3 contributors - see full revision history and disclosures

Systems:

Musculoskeletal

Synonyms:

HKA angle
Hip knee ankle angle

The hip-knee-ankle angle (HKA) measures the angulation between the mechanical axes of the femur and tibia ¹. The HKA is useful in quantifying the degree of valgus or varus alignment in the knee. It is also used in assessing post-operative knee alignment after total knee replacement ¹.

Measurement

The HKA is measured on a weight-bearing, full-length AP lower limb radiograph. The first line is drawn from the femoral head to the femoral intercondylar notch, while the latter from the tibial interspinous point to the tibial mid-plafond. The HKA is defined as the angle between these two lines ².

Interpretation

Normal values in children

Normal knee alignment varies during childhood. Genu varum is physiological from birth to 18-24 months of age. Valgus alignment is normal during development until 7 years ³. Adult valgus alignment is present after this age. HKA cannot be measured accurately until a child is able to stand independently ⁴.

Normal values in adults

For a knee in neutral alignment, the HKA angle is approximately 1-1.5° varus. However, in healthy individuals, the HKA can vary between 1° valgus and 3.2° varus ¹.