Reliability and Agreement of Four Radiographic Methods for Measuring Posterior Tibial Slope on Lateral Knee Radiographs

Year 2025, Volume: 32 Issue: 4, 327 - 335, 01.12.2025

Yavuz Yüksel , Özkan Köse

https://doi.org/10.17343/sdutfd.1771453

Abstract

Objective: The posterior tibial slope (PTS) is a critical anatomical parameter influencing knee biomechanics and ligamentous stability. Despite its clinical relevance, no consensus exists on the most reliable radiographic method for measuring PTS. This study aimed to evaluate the inter- and intra-observer reliability and agreement of four radiographic techniques for PTS measurement on standard lateral knee radiographs.
Material and Method: A retrospective analysis was conducted on 70 adult patients with high-quality true lateral knee radiographs. Four commonly used methods were applied to measure the PTS: the fibular shaft axis (FSA), anterior cortical line (ACL), posterior cortical line (PCL), and proximal anatomical axis (PAA). Two experienced observers performed all measurements twice, 15 days apart, using a standardized protocol. Intraclass correlation coefficients (ICCs) were calculated to assess reliability, and Pearson correlation coefficients were used to evaluate the agreement between measurements and demographic characteristics.
Results: All four methods showed excellent intra-observer reliability (ICC, range 0.916–0.975) and good-to-excellent inter-observer reliability (ICC, range 0.813–0.968). Mean PTS values differed by method: ACL 12.4° ± 3.2°, PCL 7.2° ± 3.1°, FSA 10.1° ± 3.2°, PAA 9.6° ± 3.0° (p = 0.001). Pairwise correlations were strong for all methods (p < 0.001). PTS showed no significant association with age, sex, height, weight, or body mass index.
Conclusions: Although reliability was high for all techniques, differences in absolute values indicate that methods are not interchangeable. Standardized reference axes should be specified to ensure consistent reporting across clinical and research settings.

Keywords

posterior tibial slope , knee radiograph , measurement reliability , observer agreement , anatomical axis

Ethical Statement

Alaaddin Keykubat University Ethics Committee approved the study protocol. Date:11.06.2025 Issue:10-2. The study was conducted in line with the principles of the "Helsinki Declaration".

References

• 1. Shelburne KB, Kim HJ, Sterett WI, Pandy MG. Effect of posterior tibial slope on knee biomechanics during functional activity. J Orthop Res. 2011;29(2):223-31. doi: 10.1002/jor.21242.
• 2. Zeng C, Borim FM, Lording T. Increased posterior tibial slope is a risk factor for anterior cruciate ligament injury and graft failure after reconstruction: A systematic review. J ISAKOS. 2025;12:100854. doi: 10.1016/j.jisako.2025.100854.
• 3. Diconi AF, Roman MD, Cristian AN, Boicean AG, Mohor CI, Ion NCI, Bocea BA, Teodoru CA, Oprinca GC, Fleaca SR. The effects of biomechanical loading on the tibial insert after primary total knee arthroplasty: A systematic review. J Clin Med. 2025;14(4):1043. doi: 10.3390/jcm14041043.
• 4. Dejour H, Bonnin M. Tibial translation after anterior cruciate ligament rupture. Two radiological tests were compared. J Bone Joint Surg Br. 1994;76(5):745-9.
• 5. Yoo JH, Chang CB, Shin KS, Seong SC, Kim TK. Anatomical references to assess the posterior tibial slope in total knee arthroplasty: A comparison of 5 anatomical axes. J Arthroplasty. 2008;23(4):586-92. doi: 10.1016/j.arth.2007.05.006.
• 6. Brandon ML, Haynes PT, Bonamo JR, Flynn MI, Barrett GR, Sherman MF. The association between posterior-inferior tibial slope and anterior cruciate ligament insufficiency. Arthroscopy. 2006;22(8):894–9. doi: 10.1016/j.arthro.2006.04.098.
• 7. Hendrix ST, Barrett AM, Chrea B, Replogle WH, Hydrick JM, Barrett GR. Relationship Between Posterior-Inferior Tibial Slope and Bilateral Noncontact ACL Injury. Orthopedics. 2017;40(1):e136-e140. doi: 10.3928/01477447-20161013-06.
• 8. Hashemi J, Chandrashekar N, Mansouri H, et al. Shallow medial tibial plateau and steep medial and lateral tibial slopes: new risk factors for anterior cruciate ligament injuries. Am J Sports Med. 2010;38(1):54–62. doi:10.1177/0363546509349055.
• 9. Hohmann E, Bryant A, Reaburn P, Tetsworth K. Is there a correlation between posterior tibial slope and non-contact anterior cruciate ligament injuries? Knee Surg Sports Traumatol Arthrosc. 2011;19(Suppl 1):S109–14. doi:10.1007/s00167-011-1547-4
• 10. Sonnery-Cottet B, Archbold P, Cucurulo T, et al. The influence of the tibial slope and the size of the intercondylar notch on rupture of the anterior cruciate ligament. J Bone Joint Surg Br. 2011;93(11):1475–8. doi:10.1302/0301-620x.93b11.26905.
• 11. Hees T, Zielke J, Petersen W. Effect of anterior tibial bowing on measurement of posterior tibial slope on conventional X-rays. Arch Orthop Trauma Surg. 2023;143(6):2959-2964. doi: 10.1007/s00402-022-04507-0.
• 12. Ni QK, Song GY, Zhang ZJ, Zheng T, Cao YW, Zhang H. Posterior tibial slope measurements based on the full-length tibial anatomic axis are significantly increased compared to those based on the half-length tibial anatomic axis. Knee Surg Sports Traumatol Arthrosc. 2022;30(4):1362-1368. doi: 10.1007/s00167-021-06605-9.
• 13. Hiyama S, Rao RP, Xie F, Takahashi T, Takeshita K, Pandit H. Comparative analysis of posterior tibial slope measurements: Accuracy and reliability of radiographs and CT. J Orthop. 2025;68:62-67. doi: 10.1016/j.jor.2025.01.037.
• 14. Garra S, Li ZI, Triana J, Savage-Elliott I, Moore MR, Kanakamedala A, Campbell K, Alaia M, Strauss EJ, Jazrawi LM. The influence of tibial length on radiographic posterior tibial slope measurement: How much tibia do we need? Knee. 2024;49:167-175. doi: 10.1016/j.knee.2024.06.005.
• 15. Kacmaz IE, Topkaya Y, Basa CD, Zhamilov V, Er A, Reisoglu A, Ekizoglu O. Posterior tibial slope of the knee measured on X-rays in a Turkish population. Surg Radiol Anat. 2020;42(6):673-679. doi: 10.1007/s00276-020-02430-w.
• 16. Medda S, Kundu R, Sengupta S, Pal AK. Anatomical variation of posterior slope of tibial plateau in adult Eastern Indian population. Indian J Orthop. 2017;51(1):69-74. doi: 10.4103/0019-5413.197545.
• 17. Abdul W, Jones M, Haslhofer D, Motesharei A, Astrinakis E, Lee J, Ball SV, Williams A. Posterior tibial slope measurements show a high degree of variability. Knee Surg Sports Traumatol Arthrosc. 2025 Jun 29. doi: 10.1002/ksa.12733.
• 18. Peez C, Waider C, Deichsel A, Briese T, Palma Kries LK, Herbst E, Raschke MJ, Kittl C. Proximal tibial anatomical axis and anterior tibial cortex-based measurements of posterior tibial slope on lateral radiographs differ least from actual posterior tibial slope-A biomechanical study. J Exp Orthop. 2024;11(4):e70108. doi: 10.1002/jeo2.70108.
• 19. Bonett DG. Sample size requirements for estimating intraclass correlations with desired precision. Stat Med. 2002;21:1331–5. doi: 10.1002/sim.1108
• 20. Koo TK, Li MY. A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research. J Chiropr Med. 2016;15(2):155-63. doi: 10.1016/j.jcm.2016.02.012. Erratum in: J Chiropr Med. 2017;16(4):346. doi: 10.1016/j.jcm.2017.10.001.
• 21. Lee SH, Yoo JH, Kwak DK, Kim SH, Chae SK, Moon HS. The posterior tibial slope affects the measurement reliability regarding the radiographic parameter of the knee. BMC Musculoskelet Disord. 2024;25(1):202. doi: 10.1186/s12891-024-07330-3.
• 22. Fletcher AN, Liles JL, Pereira GF, Danilkowicz RM, Amendola A, Riboh JC. The Intrarater and inter-rater reliability of radiographic evaluation of the posterior tibial slope in pediatric patients. J Pediatr Orthop. 2021;41(6):e404-e410. doi: 10.1097/BPO.0000000000001792.
• 23. Clinger BN, Plaster S, Passarelli T, Marshall J, Wascher DC. Differentiation in posterior tibial slope by sex, age, and race: A cadaveric study utilizing 3-dimensional computerized tomography. Am J Sports Med. 2022;50(10):2698-2704. doi: 10.1177/03635465221108187.
• 24. Pangaud C, Laumonerie P, Dagneaux L, LiArno S, Wellings P, Faizan A, Sharma A, Ollivier M. Measurement of the posterior tibial slope depends on ethnicity, sex, and lower limb alignment: A Computed tomography analysis of 378 healthy participants. Orthop J Sports Med. 2020;8(1):2325967119895258. doi: 10.1177/2325967119895258.
• 25. Weinberg DS, Williamson DF, Gebhart JJ, Knapik DM, Voos JE. Differences in medial and lateral posterior tibial slope: An osteological review of 1090 tibiae comparing age, sex, and race. Am J Sports Med. 2017;45(1):106-113. doi: 10.1177/0363546516662449.