Effectiveness of Total Knee Arthroplasty on Pain Reduction and Functional Improvement in Elderly Patients: A Quasi-Experimental Study

Abstract

Background:

Knee osteoarthritis (OA) significantly impairs mobility and quality of life in elderly patients. Total knee arthroplasty (TKA) is a well-established surgical intervention to alleviate severe pain and improve knee function. This study aimed to evaluate the effect of TKA on pain severity and knee joint function in patients aged 60–70 years.

Materials and Methods:

This quasi-experimental study included 40 patients who underwent TKA at a teaching hospital between August 2021 and February 2023. Pain severity and knee function were assessed using the Visual Analog Scale (VAS) and the Knee Society Score (KSS), respectively. Assessments were performed preoperatively and at 3 and 6 months postoperatively.

Results:

The study included 31 women and 9 men, with a mean age of 65.20 ± 3.46 years and an average BMI of 28.7 ± 3.4 kg/m². A significant reduction in pain was observed, with mean VAS scores decreasing from 8.40 preoperatively to 3.05 at 6 months postoperatively (P < .001). Knee function improved markedly, with the KSS scores increasing from 36.13 preoperatively to 75.75 at 6 months (P < .001). Both pain intensity and knee function showed significant improvements at each time point, with continued benefits observed over time.

Conclusions:

TKA significantly reduced pain and improved knee joint function in elderly patients. These findings support the effectiveness of TKA as a treatment for knee osteoarthritis, highlighting its potential to enhance the quality of life in the elderly population. Further research is recommended to explore the long-term outcomes and factors that influence patient satisfaction.

INTRODUCTION

Osteoarthritis (OA) of the knee is a prevalent degenerative joint disease that significantly affects mobility and quality of life, particularly among the elderly.[1,2] Knee OA impacts millions of individuals worldwide. Its prevalence has been increasing owing to demographic shifts, such as an aging population and rising obesity rates.[3,4] The disease is characterized by the progressive deterioration of articular cartilage, alterations in subchondral bone, and inflammation, which collectively contribute to pain, stiffness, and functional impairments.[5,6]

The management of knee OA typically begins with conservative approaches, including physical therapy, weight management, and pharmacological treatments.[7]

TKA has demonstrated considerable success in alleviating pain and improving function in patients with end-stage knee OA. A systematic review by Shan et al.[8] reported substantial improvements in pain relief, functional ability, and quality of life following TKA, with these benefits generally sustained over long-term follow-up periods. Furthermore, recent advancements in surgical techniques, implant technology, and perioperative care have contributed to enhanced outcomes and reduced complication rates.[9]

The decision to proceed with TKA involves a complex evaluation of individual factors, including age, comorbidities, and functional expectations.[10] Historically, TKA was predominantly considered for older patients; however, emerging evidence suggests that it may also be beneficial for younger, more active individuals with severe OA.[11] The optimal timing for surgery remains debated, with some studies proposing that earlier intervention could yield better functional results.[4,12]

Despite the overall efficacy of TKA, some patients report dissatisfaction or less-than-optimal outcomes postsurgery.[13] Contributing factors may include the severity of preoperative pain, psychological factors, and unrealistic expectations.[14] Therefore, thorough preoperative assessment and effective patient education are crucial for maximizing surgical outcomes and patient satisfaction.[15]

Given the increasing global burden of knee OA, there is a pressing need for evidence-based strategies to optimize its management across various populations.[16] Knee osteoarthritis (OA) is a significant and growing public health challenge, particularly among the aging population.[17] Globally, approximately 10% of men and 13% of women aged ≥60 years are affected by symptomatic knee OA, contributing substantially to disability and increased healthcare costs.[17] As the prevalence of this degenerative condition continues to rise, the need for optimized, evidence-based management strategies tailored to diverse demographic groups becomes even more urgent. TKA has consistently demonstrated substantial efficacy in patients with end-stage osteoarthritis who do not respond to conservative treatment approaches, such as physical therapy, weight management, and pharmacological interventions.[18] However, there remains a paucity of literature specifically examining short- to medium-term TKA outcomes in the elderly population. The primary aim of this study was to evaluate the effectiveness of TKA in reducing pain severity and improving knee joint functionality among elderly patients aged 60–70 years with advanced knee OA. Specifically, this study aimed to assess changes in patient-reported pain levels using the validated Visual Analog Scale (VAS) and evaluate functional outcomes, including range of motion and the ability to perform daily living activities using the Knee Society Score (KSS). This study aimed to elucidate the postoperative recovery trajectory and overall therapeutic efficacy of TKA over 6 months by focusing on this specific age cohort. The outcomes of our study are expected to provide critical insights for optimizing patient selection criteria and refining postoperative management, thereby enhancing evidence-based clinical decision-making and ultimately improving mobility and quality of life in elderly patients with severe knee OA.

MATERIALS AND METHODS

Study design and setting

This quasi-experimental study included 40 patients who underwent total knee arthroplasty (TKA) at Kashani Hospital, the primary referral center in Isfahan Province, Iran, between August 2021 and February 2023. This study aimed to evaluate the effect of TKA on pain severity and knee joint function. The demographic information collected included age, gender, body mass index (BMI), pain severity, and knee joint function. All patient data were gathered by a trained researcher from the medical records and histories of patients who underwent TKA. Pain severity and knee function were evaluated before and after surgery using the Visual Analog Scale (VAS) and the Knee Society Score (KSS).

Participants

The inclusion criteria for this study were patients aged between 60 and 70 years who were diagnosed with advanced knee osteoarthritis and required total knee arthroplasty based on a comprehensive clinical evaluation by an orthopedic specialist. All included patients presented with varus deformity of the knee before the procedure. Eligible patients were required to be in good health without significant comorbidities such as uncontrolled diabetes, severe cardiovascular disease, or active infections, which could compromise surgical outcomes. Additionally, patients with a body mass index (BMI) within the range of 18.5-30 kg/m² were included to minimize the influence of extreme obesity on postoperative recovery and knee function. All participants provided written informed consent and demonstrated a willingness to adhere to the postoperative rehabilitation protocols. Patients were excluded from the study if they had a history of previous knee surgery on the affected joint, were diagnosed with inflammatory arthritis (such as rheumatoid arthritis), or had severe musculoskeletal deformities that might complicate the surgical procedure or affect the postoperative outcomes. Other exclusion criteria included chronic use of immunosuppressive drugs, current cancer treatment, and any neurological or cognitive impairments that could hinder postoperative rehabilitation. This rigorous selection process was designed to ensure a homogeneous study population, allowing for a more accurate assessment of the effects of total knee arthroplasty on pain and knee joint function.

Surgical procedure and postoperative protocol

All surgical procedures were performed by a single senior orthopedic surgeon to maintain uniformity in the applied technique. Total knee arthroplasty (TKA) was performed using a mechanical alignment approach with the aim of restoring the neutral mechanical axis of the lower limb. The procedure was performed under spinal anesthesia with the patient in the supine position. A longitudinal midline incision was made over the knee, followed by a medial parapatellar arthrotomy to expose the knee joint. The patella was everted to allow for complete access to the femur, tibia, and joint surfaces. The distal femur and proximal tibia were resected using intramedullary and extramedullary alignment guides to create bone surfaces perpendicular to the mechanical axis of the leg. Meticulous bone cuts accommodated the femoral and tibial components and ensured proper alignment and rotation. Posterior-stabilized (PS) prostheses were used in all patients to enhance joint stability and accommodate any soft tissue imbalances. Trial components were then inserted to evaluate ligament balance, stability, and range of motion (ROM), with soft tissue release performed if necessary to achieve optimal alignment. The patella was resurfaced in all the cases. Once satisfactory alignment and stability were confirmed, the final prosthetic components were cemented in place, and the knee was thoroughly irrigated before closing the arthrotomy. The wound was closed in layers, and a sterile dressing was applied. Postoperative care followed a standardized protocol, focusing on pain management, anticoagulation, and early mobilization. Weight bearing was initiated as tolerated on the first postoperative day. Physical therapy began within the first 24 h after surgery with the aim of promoting early functional recovery through a structured rehabilitation regimen. This included active-assisted ROM exercises, quadriceps isometric contractions, and assisted ambulation.[17,19] Assistive devices, such as walkers or crutches, were provided to the patients to ensure safe mobilization during the early recovery phase. The goal was to achieve sufficient balance, functional stability, and muscle strength within the first-week postsurgery, allowing a smooth transition to unassisted walking.[18,20] The emphasis on early mobilization was designed to enhance outcomes, reduce postoperative complications, and facilitate return to daily activities. Details regarding the postoperative medication regimen, including antibiotics, analgesics, and anticoagulants, were also standardized to ensure consistency in patient care.

Outcome measures

Outcome measures were assessed both preoperatively and 6 months postoperatively using the Knee Society Score (KSS) as the primary metric. The KSS is a comprehensive evaluation tool that measures pain, function, and knee range of motion, incorporating both subjective and objective components. The Visual Analog Scale (VAS) was also used to quantify pain and establish associations between knee function and implant positioning. The severity of pain was assessed using the VAS, a well-established tool allowing patients to rate their pain on a scale from 0 (no pain) to 10 (worst pain).[21] Furthermore, the KSS provides a detailed appraisal of knee function, encompassing pain, stability, range of motion, and the ability to perform daily activities, such as walking and stair climbing.[1]

Sample size determination

The sample size was calculated considering a statistical power of 80% and a confidence level of 95%, with standard deviations of 5.58 and 7.05, a minimum detectable difference of 5.5, and factoring in a 10% dropout rate. Consequently, 40 participants were included in the study.

Statistical analysis

Statistical analysis was performed using SPSS version 26 (SPSS Inc., Chicago, IL, USA). Descriptive statistics were calculated to summarize the demographic data and outcome measures, with the results reported as mean ± standard deviation (SD) and 95% confidence intervals (CI). Repeated measures analysis of variance (ANOVA) was employed to evaluate the changes in pain intensity and knee function over three time points: Before surgery, 3 months, and 6 months postsurgery. Mauchly’s test of sphericity was conducted to assess whether the assumption of sphericity was satisfied. If the assumption was violated, the Greenhouse-Geisser correction was applied. Post-hoc comparisons were made using the Bonferroni correction to determine the specific time points at which significant changes occurred. A significance level of P < .05 was set for all statistical tests.

RESULTS

The analysis examined data from 40 patients who underwent total knee arthroplasty (TKA). Among the participants, 77.50% were female and 22.50% were male. The average age of the patients was 65.20 ± 3.46 years. The average body mass index (BMI) was 28.7 ± 3.4 kg/m².

A significant reduction in pain intensity was observed throughout the 6-month period following the surgery. The mean pain score decreased from 8.40 ± 0.87 before surgery to 5.25 ± 0.81 three months after surgery, and further declined to 3.05 ± 1.01 six months postoperatively, indicating a statistically significant improvement (P < .001). Knee function also demonstrated a significant improvement over the same period. The mean Knee Society Score increased from 36.13 ± 7.97 before surgery to 59.38 ± 8.86 3 months postsurgery, and further to 75.75 ± 8.44 6 months postsurgery, reflecting a statistically significant enhancement in knee function (P < .001) [Table 1].

Table 1.

Comparison of pain intensity and knee performance of participants before surgery and at 3 and 6 months postsurgery

Variable		Time Point		Mean±SD		95% CI		P**
Pain intensity		Before surgery		8.40±0.87		(8.12, 8.68)
		3 months postsurgery		5.25±0.81		(4.99, 5.51)
		6 months postsurgery		3.05±1.01		(2.72, 3.37)
Knee function		Before surgery		36.13±7.97		(33.57, 38.67)		<.001*
		3 months postsurgery		59.38±8.86		(56.54, 62.20)
		6 months postsurgery		75.75±8.44		(73.05, 78.45)

*Statistical significance at P<0.001. **Repeated measures ANOVA was used to determine significant differences across time points

Mauchly’s test was used to assess the assumption of sphericity for both pain intensity and knee function scores. The results for pain intensity (P = .053, Mauchly’s W = 0.857, Chi-square = 5.892) and knee function (P = .129, Mauchly’s W = 0.898, Chi-square = 4.096) indicated that the assumption of sphericity was not violated. Repeated measures ANOVA demonstrated significant improvements in both pain intensity and knee function at the 3- and 6-month marks compared to the preoperative baseline (P < .001). Additionally, a significant difference was observed between the 3- and 6-month follow-up periods, indicating the continued benefits of TKA over time (P < .001) [Table 2].

Table 2.

Changes in pain intensity and knee function scores at different time points

Variable		Time Point Comparison		Mean Difference		Standard Error (SE)		95% CI		P**
Pain intensity		Preoperative vs. 3 months		3.150*		0.150		(2.77, 3.52)		<0.001
		Preoperative vs. 6 months		5.350*		0.207		(4.83, 5.87)		<0.001
		3 months vs. 6 months		2.200*		0.172		(1.77, 2.6)		<0.001
Knee function		Preoperative vs. 3 months		−23.250*		1.168		(−26.171, −20.33)		<0.001
		Preoperative vs. 6 months		−39.625*		1.459		(−43.27, −35.97)		<0.001
		3 months vs. 6 months		−16.375*		1.160		(−19.277, −13.47)		<0.001

*The mean difference is significant at the 0.05 level. **Adjustment for multiple comparisons: Bonferroni.

DISCUSSION

This study aimed to investigate the effectiveness of total knee arthroplasty (TKA) on pain severity and functional improvement in patients aged 60–70 years with osteoarthritis over a 6-month period. The results demonstrated significant reductions in pain and marked improvements in knee function following TKA, supporting its efficacy as a treatment for severe knee osteoarthritis in elderly patients.

The average age of the participants in this study was 65 years, indicating that they were susceptible to arthritis. Although osteoarthritis is often known as an age-related disease, evidence suggests that it is also common in young individuals.[22] This disease occurs in young individuals due to various reasons such as obesity, intense physical activity, injury, and trauma. Young individuals often opt for noninvasive methods like painkillers, activity modification, joint injections, and physiotherapy for treatment and avoid surgery.[23] However, studies have shown that TKA has fewer complications in young patients compared to older individuals, and the lifespan of the replaced joint is longer in young patients.[23,24] In cases of acute osteoarthritis, choosing a treatment path for young individuals is a clinical challenge. These patients are known as therapeutic gaps because they are either too young for knee joint replacement surgery or unwilling to undergo surgery.[22,25]

Most participants in this study were women, and studies also show that osteoarthritis is twice as common in women as in men.[26,27] The exact cause of this is not fully understood, but multiple factors play a role, such as a decrease in estrogen levels. This hormone plays a crucial role in cartilage health; during menopause, estrogen levels decrease in women, increasing the risk of osteoarthritis.[28,29] It has also been stated that symptoms of this disease, such as joint pain and decreased function, occur more in women than in men.[30,31] The exact cause of this issue is not fully understood, but studies have attributed it to factors such as a range of biological factors (such as hormonal and neural factors), anatomical differences in women compared to men, muscle strength, and laxity of ligaments.[31,32] The results of this study showed a significant reduction in the average pain scores and a significant increase in knee function quality after surgery. These results indicate a positive impact of the TKA on patients. Examination of different questionnaire times demonstrated statistically significant differences in pain severity and knee function at 3 and 6 months postsurgery compared to the presurgery status. Additionally, there was a significant difference in pain intensity and knee function at 6 months compared to 3 months postsurgery.

In the study by Williams et al.,[33] the satisfaction level with knee function in 486 osteoarthritis patients who underwent the TKA was examined. 77% of patients reported complete satisfaction with their knee function after surgery. Although the questionnaires in this study had different dimensions and were different from those in the current study, both studies reported improved knee function postsurgery. Furthermore, Maempel et al.[23] conducted research on 3144 elderly patients between 75 and 80 years old who underwent TKA. Their investigation concentrated on postoperative complications in older adults, revealing decreased pain and notable enhancement in knee functionality following the procedure. The study findings have important clinical implications, showing that TKA effectively reduces pain and improves knee function in elderly patients with advanced osteoarthritis. This study suggests that TKA should be considered a viable treatment option when conservative measures are unsuccessful, providing valuable insights for clinical decision-making and potentially leading to better patient outcomes and quality of life.

This study had several limitations. The nonrandomized design limits our ability to draw causal inferences because of the absence of random allocation, which may have introduced selection bias and affected the representativeness and generalizability of our findings. Unmeasured confounding factors, such as underlying comorbidities, may have influenced the outcomes, thus impacting the reliability of our results. In addition, the 6-month follow-up period was insufficient to assess the long-term effects of total knee arthroplasty. In addition, our study did not incorporate specific patient satisfaction measures or quality-of-life assessments. Future research should include validated instruments such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) or the Short Form-36 (SF-36) to provide a more comprehensive evaluation of TKA outcomes, including patient satisfaction levels. Therefore, investigating these factors in future studies could lead to a deeper understanding of the factors affecting patient pain assessment and provide more precise control strategies.

We recommend that future studies employ randomized controlled designs with larger sample sizes to enhance the statistical power and credibility. Extending the follow-up period would allow for the evaluation of long-term outcomes and durability of surgical benefits. Including patients with various chronic diseases could help to examine the effects of knee joint replacement across different populations. While we attempted to control for confounding factors in pain assessments, a more thorough investigation of these variables in future studies could deepen the understanding of the factors affecting patient outcomes and enable more precise control strategies.

CONCLUSION

This quasi-experimental study provides compelling evidence for the efficacy of TKA in alleviating pain and enhancing knee joint function in elderly patients aged 60–70 years with advanced knee osteoarthritis. The results demonstrated statistically significant improvements in pain intensity and knee function scores at 3 and 6 months postsurgery compared with preoperative levels, with continued benefits observed over time. These findings underscore the value of TKA as a treatment option for elderly patients with severe knee osteoarthritis, offering the potential to improve the quality of life and restore functional independence.

Ethics approval and consent to participate

This study was conducted in compliance with the Helsinki Declaration and was approved by the Institutional Review Board and Ethics Committee of the Isfahan University of Medical Sciences (IR.MUI.MED.REC.1402.074). Informed consent was obtained from all patients prior to their participation in the study.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.