Osteoarthritis is the most common Orthopaedic disorder; it is a chronic disease which primarily affects cartilage and subchondral bone and surrounding synovial structures. Knee osteoarthritis is a highly prevalent condition in Indian population, which leads to disabling pain and functional limitations.[1] Rise in the geriatric population is responsible for increased prevalence of Knee OA. Pain, difficulty in walking and other functional activities are major complaints of patients with knee OA. Prevalence of Knee osteoarthritis in India ranges between 22-30%.[2] The development of knee osteoarthritis is influenced by several risk factors, including advancing age, female sex, obesity, and previous knee trauma. Age-related degenerative changes are the strongest predictor, with radiographic evidence demonstrating a high prevalence of knee OA among individuals older than 65 years. Females are affected more frequently than males, particularly after menopause. Obesity further increases the risk by causing excessive mechanical loading, chronic inflammation, altered body composition, and reduced muscle strength, while previous knee injury predisposes individuals to secondary osteoarthritis [2]. Management of knee osteoarthritis depends on disease severity. Early-stage disease is primarily treated with pharmacotherapy, lifestyle modification, and physiotherapy, whereas Total Knee Arthroplasty is indicated for patients with advanced disease who continue to experience severe pain and functional disability despite conservative treatment [3]. Total Knee Arthroplasty (TKA) is the gold standard surgical treatment for end-stage knee osteoarthritis, providing significant pain relief, improved joint function, and enhanced quality of life. The procedure involves replacing the damaged knee joint surfaces with prosthetic components. Although knee osteoarthritis predominantly affects the medial tibiofemoral compartment, degenerative changes of the patellofemoral joint are also common and may result in persistent anterior knee pain and functional limitation. Patellar resurfacing is frequently performed to address these symptoms; however, its routine use remains controversial. Evidence suggests that approximately 25% of patients who do not undergo patellar resurfacing experience poorer postoperative clinical outcomes, highlighting the potential importance of appropriate patellar management during TKA [4]. Postoperative functional recovery is particularly important in the Indian population, where routine activities commonly involve prolonged walking, stair climbing, and squatting. The thickness of the resurfaced patella may vary depending on the extent of patellar degeneration and the surgeon's intraoperative judgment, potentially influencing patellofemoral biomechanics and postoperative outcomes. However, evidence regarding the prognostic significance of postoperative patellar thickness following Total Knee Arthroplasty (TKA) remains limited. Therefore, the present study was undertaken to evaluate the effect of postoperative patellar thickness on clinical and functional outcomes after TKA by assessing its correlation with postoperative Knee Society Score (KSS) and Kujala Score. Additionally, the study aimed to determine whether the difference between preoperative and postoperative patellar thickness is associated with postoperative clinical and functional outcomes, thereby providing evidence for optimal patellar thickness restoration during TKA.

Study Design and Setting This prospective observational study was conducted between August 2025 and July 2026 at the Department of Orthopaedics, KD hospital, Ahmedabad, Gujarat, India. The study included patients undergoing primary Total Knee Arthroplasty (TKA) for primary knee osteoarthritis. Institutional Ethics Committee approval was obtained before commencement of the study, and written informed consent was obtained from all participants. Study Population All consecutive patients undergoing primary TKA during the study period were screened for eligibility. Patients fulfilling the inclusion criteria and willing to participate were enrolled. Inclusion Criteria • Patients undergoing primary Total Knee Arthroplasty for primary osteoarthritis. • TKA performed using the medial parapatellar surgical approach. • Patients providing written informed consent. Exclusion Criteria • Patients unwilling to participate. • Revision Total Knee Arthroplasty. • Active local or systemic infection. • Complex primary TKA. • Periprosthetic fracture occurring during the study period. • TKA performed for indications other than primary osteoarthritis. Data Collection Demographic and clinical data were collected from hospital records and direct patient assessment. All participants underwent preoperative evaluation, including detailed history, clinical examination, and standard radiographic assessment using weight-bearing anteroposterior and lateral radiographs of the knee. Patellar thickness was measured intraoperatively before and after resurfacing using a sterile Vernier calliper and recorded in millimetres (mm). All measurements were performed by the operating surgeon. Surgical Procedure All procedures were performed by a single experienced orthopedic surgeon using the subvastus approach. Standard cemented Total Knee Arthroplasty was performed using femoral, tibial, polyethylene, and patellar components. Patellar resurfacing was carried out in all patients following standard surgical principles while maintaining appropriate patellar alignment and tracking. Standard perioperative antibiotic prophylaxis, thromboprophylaxis, pain management, and rehabilitation protocols were followed for all patients. Outcome Measures Patients were evaluated preoperatively and at six months postoperatively. The primary clinical outcome was assessed using the Knee Society Score (KSS), while functional outcome was evaluated using the Kujala Anterior Knee Pain Score. Pain intensity was assessed using the Visual Analogue Scale (VAS). Knee Society Score evaluation included pain, stability, range of motion, walking distance, stair climbing, and functional activities according to the modified Knee Society Scoring System. [5-7]. The primary study variable was postoperative patellar thickness. Correlation analyses were performed between postoperative patellar thickness and postoperative KSS and Kujala scores. Additionally, the difference between preoperative and postoperative patellar thickness was calculated and correlated with postoperative clinical and functional outcomes. Postoperative Rehabilitation and Follow-up All patients underwent a standardized postoperative rehabilitation protocol. Static quadriceps exercises and knee range-of-motion exercises were initiated on the first postoperative day, followed by progressive knee mobilization, full weight-bearing as tolerated, and supervised physiotherapy. Patients were followed up at 2 weeks, 1 month, 3 months, and 6 months after surgery. Final assessment was performed at the six-month follow-up, during which postoperative complications, VAS score, Kujala Score, and Knee Society Score were recorded. Statistical Analysis Data were entered into Microsoft Excel and analyzed using GraphPad version 3.0. Continuous variables were expressed as mean ± standard deviation (SD), whereas categorical variables were presented as frequencies and percentages. Pearson's correlation coefficient was used to determine the relationship between postoperative patellar thickness and postoperative Knee Society Score (KSS) and Kujala Score, as well as between the change in patellar thickness and postoperative outcomes. A p-value of <0.05 was considered statistically significant.

This study investigated the impact of Patella thickness change on the Kujala and KSS scores in individuals undergoing Total Knee Replacement (TKR). The data were analyzed to determine the improvement in these scores pre- and post-intervention, considering different categories of Patella thickness change. Table 1. Demographic characteristics of study participants Parameters Frequency Percent (%) Age (years) 40 - 49 3 5.88 50 - 59 14 27.5 60 - 69 20 39.2 70 - 79 12 23.5 80+ 2 3.92 Gender Female 42 82.4 Male 9 17.6 Affected side Left 23 45.1 Right 28 54.9 Table 1 shows the demographic characteristics of the 51 study participants. Most patients were aged 60–69 years (39.2%), followed by 50–59 years (27.5%) and 70–79 years (23.5%). Three patient (5.88%) belonged to the 40–49, and 2 patients were belonging to ≥80 years age groups. The study population comprised predominantly females (82.4%), while males accounted for 17.6%. Regarding the affected side, the right knee was involved in 54.9% of patients, whereas the left knee was affected in 45.1%. Overall, the study population mainly consisted of elderly female patients with a slight predominance of right-sided knee involvement. Table 2. Pre- and post-surgical patellar thickness distribution among study participants Measurement Frequency Percent (%) Pre-surgical patellar thickness 19.00 1 2.0 20.00 8 15.7 21.00 9 17.6 22.00 14 27.5 22.50 1 2.0 23.00 7 13.7 24.00 6 11.8 24.50 1 2.0 25.00 3 5.9 26.00 1 2.0 Post-surgical patellar thickness 21.00 7 13.7 22.00 20 39.2 23.00 9 17.6 23.50 1 2.0 24.00 7 13.7 24.50 1 2.0 25.00 3 5.9 25.50 1 2.0 26.00 1 2.0 26.50 1 2.0 Table 2 presents the distribution of pre- and post-surgical patellar thickness among the study participants. Preoperatively, the most common patellar thickness was 22.0 mm (27.5%), followed by 21.0 mm (17.6%) and 20.0 mm (15.7%), with measurements ranging from 19.0 mm to 26.0 mm. Postoperatively, the majority of patients had a patellar thickness of 22.0 mm (39.2%), followed by 23.0 mm (17.6%), while 21.0 mm and 24.0 mm were each observed in 13.7% of patients. Overall, postoperative patellar thickness was more uniformly distributed around 22–24 mm, indicating restoration of patellar thickness within the desired range following resurfacing. Table 3. Comparison of Pre and Post Scoring systems in different categories of patella difference Patella Difference Category Scoring System Mean ± SD P value Patella difference categories = -2.00 Pre_Kujala 35.00 ± 10.13 <0.001 Post_Kujala 72.71 ± 6.21 Pre_KSS 44 ± 8.50 <0.001 Post_KSS 171.14 ± 15.20 Patella difference categories = -1.00 Pre_Kujala 40.11 ± 6.97 <0.001 Post_Kujala 76.22 ± 6.74 Pre_KSS 51.83 ± 18.42 <0.001 Post_KSS 163.88 ± 13.62 Patella difference categories = 0.00 Pre_Kujala 38.57 ± 8.91 <0.001 Post_Kujala 79.52 ± 6.27 Pre_KSS 64.52 ± 14.92 <0.001 Post_KSS 164.21 ± 12.86 Table 3 compares the preoperative and postoperative Kujala Score and Knee Society Score (KSS) across different patellar thickness difference categories (−2 mm, −1 mm, and 0 mm). In all categories, both the Kujala Score and KSS showed a statistically significant improvement following surgery (p < 0.001). Patients with a 0 mm patellar thickness difference achieved the highest mean postoperative Kujala Score (79.52 ± 6.27), while the highest mean postoperative KSS was observed in the −2 mm difference group (171.14 ± 15.20). These findings indicate that Total Knee Arthroplasty resulted in significant improvements in both clinical and functional outcomes irrespective of the patellar thickness difference category. Table 4. Intragroup Comparison among Different scores among study participants Groups N Mean P value Different Kujala group -2.00 7 37.71 ± 8.82 0.10 -1.00 18 36.11 ± 6.27 .00 19 40.94 ± 6.58 Different KSS Group -2.00 7 127.14 ± 21.08 0.04 -1.00 18 112.05 ± 25.96 .00 19 99.68 ± 24.97 Table 4 presents the intragroup comparison of mean Kujala and Knee Society Score (KSS) across different patellar thickness difference categories. The mean Kujala scores were comparable among the −2 mm (37.71 ± 8.82), −1 mm (36.11 ± 6.27), and 0 mm (40.94 ± 6.58) groups, with no statistically significant difference (p = 0.10). In contrast, the mean KSS differed significantly across the groups (p = 0.04), with the highest score observed in the −2 mm group (127.14 ± 21.08), followed by the −1 mm group (112.05 ± 25.96) and the 0 mm group (99.68 ± 24.97), indicating a significant association between patellar thickness difference categories and KSS.

Total Knee Arthroplasty (TKA) is the standard surgical treatment for end-stage knee osteoarthritis, providing substantial pain relief and improvement in knee function. Despite the excellent long-term outcomes of TKA, the optimal management of patellar resurfacing remains controversial, particularly regarding the ideal postoperative patellar thickness. The present study evaluated the relationship between postoperative patellar thickness and clinical and functional outcomes using the Knee Society Score (KSS) and Kujala Score. The present study demonstrated significant improvement in both KSS and Kujala scores following TKA across all patellar thickness difference categories (p<0.001), confirming the effectiveness of TKA in improving clinical and functional outcomes. Patients with no difference between preoperative and postoperative patellar thickness (0 mm) achieved the highest postoperative Kujala score, suggesting that preservation of native patellar thickness may provide superior patellofemoral function and reduce anterior knee pain. Conversely, the highest postoperative KSS was observed in patients with a 2 mm increase in patellar thickness, indicating that a slight increase in patellar thickness may not adversely affect overall knee function. Furthermore, intragroup analysis revealed no significant difference in Kujala scores among the patellar thickness categories (p=0.10), whereas KSS differed significantly between the groups (p=0.04), suggesting that postoperative patellar thickness has a greater influence on overall knee performance than on anterior knee pain alone. The findings of the present study are consistent with those reported by Hsu et al., who emphasized the importance of restoring native patellar thickness during TKA to achieve satisfactory patellofemoral biomechanics and clinical outcomes. They observed that preservation of native patellar thickness was associated with favorable postoperative function without increasing complications such as patellar instability or component loosening [8]. Similarly, Saithna et al. reported that deviations from native patellar thickness, either by excessive thinning or overstuffing, adversely affected patellofemoral mechanics and clinical outcomes, underscoring the need for accurate restoration of patellar thickness during resurfacing [9]. The superior postoperative Kujala scores observed in patients with no change in patellar thickness in the present study further support these observations. However, the present findings also suggest that a modest increase in patellar thickness may be clinically acceptable. Tammachote et al. demonstrated that an average increase of approximately 2 mm following patellar resurfacing did not significantly affect postoperative knee flexion, functional scores, or patient satisfaction, indicating that mild patellofemoral overstuffing may be well tolerated when appropriate component alignment and soft tissue balancing are achieved [10]. This finding corresponds with the present study, in which patients with a 2 mm increase in patellar thickness achieved the highest postoperative KSS without deterioration in functional outcomes. Although slight increases in patellar thickness appear acceptable, excessive overstuffing of the patellofemoral joint has been associated with adverse consequences. Nam D et al. reported that increased postoperative patellar thickness may alter patellofemoral biomechanics, resulting in patellar maltracking, increased contact pressures, anterior knee pain, and a higher likelihood of revision surgery [11]. Therefore, surgeons should avoid excessive increases in patellar thickness while ensuring adequate residual bone stock and appropriate implant positioning. Resurfacing of thin native patellae remains another important surgical consideration. Nam et al. demonstrated excellent long-term implant survivorship following resurfacing of thin patellae, with a 10-year survivorship free from patellar revision of approximately 98%. Nevertheless, isolated cases of patellar loosening and periprosthetic fractures were reported, emphasizing the importance of meticulous surgical technique and careful patient selection [12]. Overall, the findings of the present study suggest that restoration of patellar thickness close to the native anatomy provides favorable patellofemoral function, while a slight increase in thickness may still yield satisfactory overall clinical outcomes. These observations reinforce the importance of individualized intraoperative assessment rather than adopting a uniform target patellar thickness for all patients. Careful balancing of patellar thickness, component positioning, and soft tissue tension remains essential for optimizing postoperative outcomes following Total Knee Arthroplasty.

The present study demonstrates that postoperative patellar thickness significantly influences clinical and functional outcomes following Total Knee Arthroplasty. Restoration of patellar thickness close to its native anatomy was associated with better patellofemoral function, while a slight increase in thickness yielded satisfactory overall knee function without compromising outcomes. These findings emphasize the importance of individualized intraoperative assessment and meticulous surgical technique to optimize patellar thickness during resurfacing. Further large-scale, long-term studies are warranted to establish standardized recommendations for optimal patellar thickness and its impact on long-term TKA outcomes.

1. Bijlsma JW, Berenbaum F, Lafeber FP. Osteoarthritis: an update with relevance for clinical practice. The Lancet. 2011 Jun 18;377(9783):2115-26. 2. Kettlekamp DB, Pryor P, Brady TA. A selective use of the variable axis knee. Orthop Trans. 1979;3:543. 3. Vaishya R, Vijay V, Demesugh DM, Agarwal AK. Surgical approaches for total knee arthroplasty. Journal of clinical orthopaedics and trauma. 2016 Apr;7(2):71. 4. Berger RA, Rubash HE, Seel MJ, Thompson WH, Crossett LS. Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clinical orthopaedics and related research. 1993 Jan 1(286):40-7. 5. Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop relat res. 1989 Nov 1;248(248):13-4. 6. Lingard EA, Katz JN, Wright RJ, Wright EA, Sledge CB, Kinemax Outcomes Group. Validity and Responsiveness of the Knee Society Clinical Rating System in Comparisonwith the SF-36 and WOMAC. JBJS. 2001 Dec 1;83(12):1856-64. 7. Odum SM, Fehring TK. Can original knee society scores be used to estimate new 2011 knee society scores?. Clinical Orthopaedics and Related Research®. 2017 Jan;475(1):160-7. 8. Hsu, H. P., Luo, C. A., Chou, Y. C., & Wu, C. C. (1996). Influence of patellar thickness on outcomes after total knee arthroplasty. Journal of Bone and Joint Surgery, 78(6), 987-993. 9. Saithna, A., Kundra, R., & Murawski, C. D. (2014). Changes in patellar thickness and knee function post-TKR. Journal of Arthroplasty, 29(10), 1845-1850. PubMed 10. Tammachote, N., Chareancholvanich, K., & Pornrattanamaneewong, C. (2023). Influence of patellar thickness changes on functional outcomes after TKR. Clinical Orthopaedics and Related Research, 481(2), 320-329. 11. Nam, D., Nunley, R. M., & Barrack, R. L. (2020). Complications associated with patellar overstuffing in total knee arthroplasty. The Journal of Knee Surgery, 33(3), 256-264. 12. Nam, D., Mahoney, O. M., & Nunley, R. M. (2023). Outcomes of patellar resurfacing in patients with thin patellae: A 10-year follow-up study. Journal of Bone and Joint Surgery, 105(7), 1234-1242