Joint line preservation is of great significance in knee replacement. Purpose. Bibliographic review and own cases revision to establish proper bone references to assess joint line Material and Methods. Retrospective assessment of 30 patients with knee osteoarthritis. A-P and lateral X-ray were evaluated. Joint line was measured from next references: medial and lateral epicondyle, medial and lateral flare, anterior tibial tubercle and head of the fibula. Outcomes. 23 women and 7 men of 71.3 (± 6.34) of age were included in this revision. Twenty-eight PS prostheses and 2 CR were assessed. No changes were observed in joint line after primary knee replacement. No big differences were related to age, sex or prostheses design. Medial flare and anterior tibial tubercle were the most precise references (83 and 70 % of cases). We found differences with statistically significance for absolute measures related to sex that were matched with the use of ratios. Conclusions. Joint line is re-established in the majority of cases after primary knee replacement. Medial flare is the easiest and reproducible bone reference in clinical practice. Femoral and tibial ratios allow mending possible changes due to sizes of the patient and mistakes related to magnification of the image.

Joint line preservation is of great significance in knee replacement. Purpose. Bibliographic review and own cases revision to establish proper bone references to assess joint line Material and Methods. Retrospective assessment of 30 patients with knee osteoarthritis. A-P and lateral X-ray were evaluated. Joint line was measured from next references: medial and lateral epicondyle, medial and lateral flare, anterior tibial tubercle and head of the fibula. Outcomes. 23 women and 7 men of 71.3 (± 6.34) of age were included in this revision. Twenty-eight PS prostheses and 2 CR were assessed. No changes were observed in joint line after primary knee replacement. No big differences were related to age, sex or prostheses design. Medial flare and anterior tibial tubercle were the most precise references (83 and 70 % of cases). We found differences with statistically significance for absolute measures related to sex that were matched with the use of ratios. Conclusions. Joint line is re-established in the majority of cases after primary knee replacement. Medial flare is the easiest and reproducible bone reference in clinical practice. Femoral and tibial ratios allow mending possible changes due to sizes of the patient and mistakes related to magnification of the image.