As advancements in total knee arthroplasty progress at an exciting pace, two areas are of special interest, as they directly impact implant design and surgical decision making. Knee morphometry considers the three-dimensional shape of the articulating surfaces within the knee joint, and knee phenotyping provides the ability to categorize alignment into practical groupings that can be used in both clinical and research settings. This annotation discusses the details of these concepts, and the ways in which they are helping us better understand the individual subtleties of each patient’s knee. Cite this article: Bone Joint J 2024;106-B(12):1363–1368

Side-to-side comparison of anatomical or functional parameters in the evaluation of unilateral pathologies of the knee joint is common practice. Generally, it is assumed that the contralateral joint provides “normal” anatomy and function and that within-subject side differences are less when compared with between-subject variability. This has advocated the use of side-to-side comparisons in a wide field of orthopaedic surgery. The aim of this study was to test the hypothesis that there are no significant differences in the morphometric knee joint dimensions between the right and the left knee of a human subject. Furthermore, it was hypothesized that side differences within subjects are smaller than inter-subject variability. In 30 pairs of human cadaver knees the morphometry of the articulating osseous structures of the femorotibial joint, the cruciate ligaments, and the mensici were measured using established measurement methods. Morphometric data were obtained either using digital callipers, radiographs, contour gauges, or cross-sectiontal scans. Data were analysed for overall side differences using the Student t-test and Pearson’s correlation coefficient and the ratio between within-subject side differences and intersubject variability was calculated. In three out of 71 morphometric dimensions there was a significant side difference, including the posterior tibial slope, the anatomical valgus alignment of the distal femur, and the position of the femoral insertion area of the ACL. In two additional parameters, including the cross-sectional area of the distal third of the ACL and PCL, within-subject side differences were larger than intersubject variability. In general, there was a positive correlation in morphometric dimensions between right and left knees in one subject. This study confirmed a good correlation in the morphometric dimensions of a human knee joint between the right and the left side. Our data support the concept of obtaining morphometric reference data from the contralateral uninjured side in the evaluation of unilateral pathologies of the knee joint. The uninjured contralateral side rather than knee joint dimensions obtained from an uninjured subject should be used as a valid control in orthopaedic practice

Purpose: There is no data concerning morphological dimensions of distal femur(DF), proximal tibia(PT) and thickness of patella(TP) in Indian population and our objective was to analyse the anthropometric data in Indian knees and to correlate them with existing knee arthroplasty systems. Methods: MRI scans of 25 patients(15M;10F) who underwent bilateral knee scans for ligamental injuries were collected. Patients with arthritis, bone loss, varus/ valgus deformity of > 150 and those with immature skeleton were excluded. The mean age was 32 years (range 18–53y). Three surgeons independently measured medio-lateral(ML), antero-posterior(AP) lengths & aspect ratio(AR) of DF, PT and TP on three occasions one week apart to account for intra & inter-observer variability. The resultant data of 50 knees was analysed using SPSS v16.0 and compared with five different knee arthroplasty systems (PFC sigma/NexGen/Scorpio/IB-II/ Gender specific knee). Results: The mean ML & AP for proximal tibia was 73.3±5.3 & 47.8±4.3 mm. The mean ML & AP (lateral condyle) for distal femur was 74.3±5.9 & 65.4±5.0 mm. The mean unresected thickness of patella was 24.7 & 21.8 mm in males & females respectively. The ML & AP showed a statistically significant positive correlation with person’s height (ML®=0.55;AP®=0.50 & p=0.01). A decrease in AR for increasing AP dimension was noted for both distal femur and proximal tibia (Tibia®=0.153;p=0.29 & Femur:®=−0.91;p=0.001). Discussion: None of the prosthesis designs mimicked this decrease in AR and NexGen infact showed increase in AR. Only Gender specific knee closely mimicked normal variation in AR and is available only for females (in India). Most of the available TKR prosthesis designs differ from true knee morphometry of Indian population. These data provides the basis for designing optimal prosthesis for people of Indian/Asian origin in UK/overseas

There is no data concerning morphological dimensions of distal femur, proximal tibia and patella in Indian population. The objective was to analyse the anthropometric data in Indian knees and to co-relate them with existing knee arthroplasty systems. MRI scans of 25 patients (15 males & 10 females) who underwent bilateral knee scans for ligamental injuries were collected. Patients with arthritis, bone loss, varus/valgus deformity of > 15 degrees and those with immature skeleton were excluded. The mean age was 32 yrs (18–53 yrs). Three surgeons independently measured medio-lateral (ML), antero-posterior(AP) dimensions & aspect ratio(AR) of distal femur, proximal tibia and unresected patellar thickness(PT) on three occasions one week apart to account for intra & inter-observer variability. The resultant data of 50 knees was analysed using SPSS v14.0 and compared with five prosthesis knee systems (PFC sigma, NexGen, Scorpio, IB-II & Gender specific knee). The mean ML & AP for proximal tibia was 73.3±5.3 & 47.8±4.3 mm. The mean ML & AP (lateral condyle) for distal femur was 74.3±5.9 & 65.4±5.0 mm. The mean PT was 24.7 & 21.8 mm in males & females respectively. The ML & AP showed a statistically significant positive correlation with the height of the person (ML r=0.55; AP r=0.50 & p=0.01). The tibial and femoral AR showed higher ratio for smaller knees & smaller ratio for larger knees i.e. decline in AR for increasing AP dimension. None of the prosthesis designs mimicked this decrease in AR and NexGen prosthesis infact showed an increase in AR. Gender differences in the morphological data were shown by variable tibial AR. Most of the available TKR prosthesis designs differ from actual knee morphometry of Indian population. These data provides the basis for designing optimal prosthesis for people of Indian/Asian origin in UK and overseas