For evaluation of the joint space, weight-bearing knee radiographs have shown better results compared with supine radiographs.3 The standard, anteroposterior (AP), weight-bearing knee radiographs are usually performed by standing on both legs. We found a number of patients with severe symptomatic knee OA who would require knee surgery. However, the joint space width was measured as KL grade I to II in both legs on standing radiographs. Re-evaluation with the use of one leg standing radiographs found that the KL grading had changed to grade III-IV (Fig.1). Also, complete cartilage loss had been confirmed during the surgery. Joint space width may be larger in both legs on standing due to avoidance of weight-bearing on the painful arthritic knee or by shared weight-bearing between both legs.

https://online.boneandjoint.org.uk/doi/full/10.1302/2046-375...

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Panewka była owalna a jej osie symetrii wynosiły
odpowiednio 54,6 mm i 53,6 mm. Dla wyznaczenia
głębokości panewki oraz kąta inklinacji i kąta antewersji
zdefiniowano oś panewki, która jest prostą przechodzącą
przez jej środek i prostopadłą do płaszczyzny obrąbka
panewkowego
http://pe.org.pl/articles/2015/5/10.pdf

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Note added at 1 hr (2020-05-11 13:37:43 GMT)
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The same technique of EBRA (Einzel-Bild-Roentgen-Analyse)7,16 (University of Innsbruck, Innsbruck, Austria) analysis of standing radiographs was used to assess the BHR group and the larger ASR patient group.

Bergmann et al20 showed that, in the standing position, the average hip joint contact force is directed 14° medially from the longitudinal axis in the anteroposterior plane and 16° anteriorly in the transverse plane. Using these data and the orientations of the acetabular components of the patients in this study, we calculated the distance from the centre of the theoretical contact patch to the superior anterior edge of the articular surface of the acetabular component (or its rim) for each patient in the standing position.
With regard to standing radiological anteversion, we recommend 10° to 20°, with the same justification and allowance for a margin of error. In the senior author’s patient group, the minimum Harris Hip Score of the 14 patients with acetabular components in this target area was 97 (mean score 99.0, mean femoral size 48.0 mm (42 to 54)).
https://online.boneandjoint.org.uk/doi/full/10.1302/0301-620...