Osteoarthritis (OA) of the knee is one of the most common chronic musculoskeletal disorders worldwide and a leading cause of pain, functional limitation, and disability among middle-aged and elderly populations. It is characterized by progressive degeneration of articular cartilage, subchondral bone remodeling, osteophyte formation, and synovial inflammation. With increasing life expectancy, rising obesity rates, and sedentary lifestyles, the global burden of knee osteoarthritis continues to increase, posing a significant public health challenge.^[1]

Radiographic evaluation remains the cornerstone for diagnosing and grading the severity of knee osteoarthritis in clinical practice. The Kellgren-Lawrence (KL) grading system is the most widely used radiographic classification, based on features such as joint space narrowing, osteophyte formation, subchondral sclerosis, and bony deformity. Despite its widespread use, the extent to which radiographic severity correlates with patients’ perceived pain and functional impairment remains controversial. Several studies have reported weak to moderate correlations between radiographic findings and clinical symptoms, highlighting a potential discordance between structural damage and patient-reported outcomes.^[2]

Pain is the primary symptom driving patients with knee OA to seek medical attention. However, pain perception in osteoarthritis is multifactorial, influenced not only by structural joint changes but also by synovial inflammation, bone marrow lesions, muscle weakness, psychosocial factors, and central pain sensitization. Functional limitation, assessed through validated scoring systems such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), often has a more direct impact on quality of life than radiographic severity alone.^[3][4]

Aim

To evaluate the correlation between radiographic severity of knee osteoarthritis and pain and functional limitation in patients with knee OA.

Objectives

1. To assess radiographic severity of knee osteoarthritis using the Kellgren-Lawrence grading system.
2. To evaluate pain intensity and functional status using validated clinical scoring systems.
3. To analyze the correlation between radiographic severity and pain and functional outcomes in knee OA.

Source of Data Data were collected from patients attending the Orthopaedics outpatient department of a tertiary care teaching hospital who were clinically diagnosed with knee osteoarthritis and fulfilled the study criteria. Study Design This was a hospital-based cross-sectional correlational study. Study Location The study was conducted in the Department of Orthopaedics at a tertiary care hospital. Study Duration The study was carried out over a period of 12 months. Sample Size A total of 80 patients diagnosed with knee osteoarthritis were included in the study. Inclusion Criteria • Patients aged ≥40 years • Clinically diagnosed cases of primary knee osteoarthritis • Patients willing to participate and provide informed consent • Availability of standard weight-bearing anteroposterior and lateral knee radiographs Exclusion Criteria • Secondary osteoarthritis due to trauma, inflammatory arthritis, or infection • History of previous knee surgery or fracture • Presence of neurological disorders affecting lower limb function • Patients with severe systemic illness limiting functional assessment Procedure and Methodology After obtaining informed consent, eligible patients were enrolled in the study. Detailed demographic and clinical information was recorded, including age, sex, body mass index, duration of symptoms, and affected knee. Standardized weight-bearing anteroposterior and lateral radiographs of the knee were obtained. Radiographic severity was graded using the Kellgren-Lawrence classification by an experienced orthopaedician blinded to clinical scores. Pain intensity was assessed using a validated pain scale, and functional status was evaluated using the WOMAC questionnaire. All assessments were performed on the same visit to minimize variability. Each patient’s pain and function scores were documented systematically. Sample Processing Radiographs were reviewed and graded, and questionnaire scores were calculated as per standard scoring guidelines. Data were checked for completeness and accuracy before entry into the database. Data Collection Data were collected using a pre-designed and pre-tested structured proforma, including demographic details, clinical findings, radiographic grades, pain scores, and functional assessment scores. Statistical Methods Data were entered into Microsoft Excel and analyzed using statistical software. Descriptive statistics were used to summarize demographic and clinical variables. Correlation between radiographic severity and pain and functional scores was assessed using appropriate correlation coefficients (Pearson or Spearman, based on data distribution). A p-value of <0.05 was considered statistically significant.

Table 1: Baseline Demographic and Clinical Characteristics of Patients with Knee Osteoarthritis (N = 80)

*Statistically significant

Table 1 presents the baseline demographic and clinical characteristics of the 80 patients with knee osteoarthritis included in the study. The mean age of the study population was 58.7 ± 8.9 years, with a 95% confidence interval (CI) of 56.7-60.6 years, which was statistically significant (p < 0.001). Females constituted a higher proportion of the study population (61.2%) compared to males (38.8%); however, the sex distribution did not show a statistically significant difference (p = 0.214). The mean body mass index (BMI) of the participants was 26.8 ± 3.4 kg/m² (95% CI: 26.0-27.6), indicating an overweight population, and this finding was statistically significant (p < 0.001). The mean duration of knee symptoms was 4.6 ± 2.1 years, with a 95% CI of 4.1-5.1 years (p < 0.001). Regarding the side affected, right knee involvement was most common (42.5%), followed by left knee (36.3%) and bilateral involvement (21.2%); however, the distribution of the affected side was not statistically significant (p = 0.638).

Table 2: Distribution of Radiographic Severity of Knee Osteoarthritis Based on Kellgren-Lawrence (KL) Grading (N = 80)

*Statistically significant

Table 2 depicts the distribution of radiographic severity of knee osteoarthritis based on the Kellgren-Lawrence grading system. Grade III (moderate osteoarthritis) was the most common radiographic grade observed, accounting for 36.2% of patients, followed by Grade II (mild osteoarthritis) in 27.5%, Grade IV (severe osteoarthritis) in 25.0%, and Grade I (doubtful osteoarthritis) in 11.3% of cases. The overall distribution of Kellgren-Lawrence grades showed a statistically significant deviation from equal distribution (p < 0.001). The mean Kellgren-Lawrence grade was 2.75 ± 0.94, with a 95% CI of 2.54-2.96, indicating that the majority of patients had moderate radiographic disease severity. This finding was also statistically significant (p < 0.001).

Table 3: Pain Intensity and Functional Status Among Patients with Knee Osteoarthritis (N = 80)

*Statistically significant

Table 3 summarizes the pain intensity and functional status of patients with knee osteoarthritis as assessed by validated clinical scoring systems. The mean Visual Analogue Scale (VAS) pain score was 6.42 ± 1.31, with a range of 3-9 and a 95% CI of 6.13-6.71, indicating moderate to severe pain levels among the study population (p < 0.001). The mean WOMAC pain score was 11.6 ± 3.4 (95% CI: 10.9-12.3), while the mean WOMAC stiffness score was 4.8 ± 1.5 (95% CI: 4.5-5.2). Functional limitation, as measured by the WOMAC function subscale, showed a mean score of 36.9 ± 8.7 (95% CI: 34.9-38.8). The overall WOMAC total score was 53.3 ± 11.6, with a 95% CI of 50.7-55.8. All pain and functional parameters were statistically significant (p < 0.001), reflecting a substantial symptom burden among patients with knee osteoarthritis.

Table 4: Correlation Between Radiographic Severity and Pain/Functional Outcomes in Knee Osteoarthritis (N = 80)

*Statistically significant

Table 4 demonstrates the correlation between radiographic severity of knee osteoarthritis and pain and functional outcomes. A strong positive correlation was observed between Kellgren-Lawrence grade and VAS pain score (r = 0.61, 95% CI: 0.44-0.74; p < 0.001), indicating increased pain intensity with advancing radiographic severity. Similarly, significant positive correlations were noted between Kellgren-Lawrence grade and WOMAC pain score (r = 0.58) and WOMAC stiffness score (r = 0.46). The strongest correlations were observed with functional outcomes, particularly between Kellgren-Lawrence grade and WOMAC function score (r = 0.69) and WOMAC total score (r = 0.72), both of which were highly statistically significant (p < 0.001).

Baseline Demographic and Clinical Characteristics (Table 1): In the present study, the mean age of patients with knee osteoarthritis was 58.7 ± 8.9 years, indicating that knee OA predominantly affected the late middle-aged to elderly population. This finding is consistent with earlier epidemiological studies by Chaturvedi R et al. (2021)[5], who reported a higher prevalence of symptomatic knee OA after the fifth decade of life due to cumulative mechanical stress and age-related cartilage degeneration.

Females constituted a larger proportion of the study population (61.2%), although the sex distribution was not statistically significant. Similar female predominance has been reported by Ribeiro IC et al. (2020)[6], who attributed this to postmenopausal hormonal changes, reduced muscle strength, and higher obesity rates among women.

The mean BMI in the present study was 26.8 ± 3.4 kg/m², placing most patients in the overweight category. This observation aligns with the findings of Özden F et al. (2020)[2], who identified increased BMI as a major modifiable risk factor for knee OA. The statistically significant duration of symptoms (4.6 ± 2.1 years) reflects the chronic and progressive nature of the disease, as also reported by Innmann MM et al. (2023)[3]. Side involvement showed no significant predominance, which is comparable to previous studies reporting variable laterality patterns without strong clinical significance.

Radiographic Severity Based on Kellgren-Lawrence Grading (Table 2): Radiographic assessment revealed that the majority of patients had moderate to severe osteoarthritis, with Grade III (36.2%) being the most common, followed by Grade IV (25.0%). This distribution is comparable to the observations of Riapesi Y et al. (2021)[7], who reported that patients presenting to tertiary care centers are more likely to have advanced radiographic disease.

The mean KL grade of 2.75 ± 0.94 indicates a predominance of established osteoarthritic changes rather than early disease. Similar mean KL grades have been reported in hospital-based studies by Alghadir AH et al. (2022)[8]. The statistically significant distribution of KL grades in the present study further supports the heterogeneous nature of structural severity among symptomatic OA patients.

Pain Intensity and Functional Status (Table 3): Patients in the present study experienced moderate to severe pain, with a mean VAS score of 6.42 ± 1.31. This is comparable to the findings of Zhu T et al. (2021)[9], who demonstrated that pain intensity in knee OA often remains high despite variable radiographic severity.

WOMAC scores indicated substantial impairment across pain, stiffness, and functional domains, with the highest burden observed in the functional subscale. These findings are consistent with Ahmed SM et al. (2020)[10], who reported that WOMAC function scores are particularly sensitive to disease severity and daily activity limitation. The statistically significant WOMAC total score observed in this study reflects the cumulative impact of pain and stiffness on physical function, reinforcing the multidimensional nature of osteoarthritis-related disability.

Correlation Between Radiographic Severity and Pain/Functional Outcomes (Table 4): The present study demonstrated a statistically significant positive correlation between KL grade and pain as well as functional impairment. A strong correlation was observed between KL grade and VAS pain score (r = 0.61), which is comparable to findings reported by Alghadir AH et al. (2022)[11], who noted moderate correlations between radiographic severity and pain intensity.

Notably, the strongest correlations were observed between KL grade and WOMAC function (r = 0.69) and WOMAC total score (r = 0.72). Similar observations were made by Bahia RK et al. (2021)[12], who reported that radiographic severity correlates more consistently with functional limitation than with pain alone. This may be explained by the fact that structural changes such as joint space narrowing and osteophyte formation have a more direct impact on mobility and physical performance than on pain perception, which is influenced by multiple biological and psychosocial factors.

The present cross-sectional correlational study demonstrated a significant association between radiographic severity of knee osteoarthritis and clinical outcomes related to pain and functional limitation. Increasing Kellgren-Lawrence grades were positively correlated with higher pain scores and, more strongly, with greater functional impairment as assessed by WOMAC indices. While pain intensity showed a moderate correlation with radiographic severity, functional limitation exhibited a stronger and more consistent relationship, suggesting that structural joint damage has a greater impact on physical function than on pain perception alone. These findings highlight the importance of integrating radiographic assessment with patient-reported outcome measures for comprehensive evaluation and individualized management of knee osteoarthritis. Radiographic grading alone may not fully capture symptom severity, emphasizing the need for a holistic approach in clinical decision-making and treatment planning. LIMITATIONS OF THE STUDY The cross-sectional design limited the ability to establish a temporal or causal relationship between radiographic severity and clinical symptoms. The sample size was relatively small and drawn from a single tertiary care center, which may limit the generalizability of the findings. Advanced imaging modalities such as MRI, which can detect early cartilage and soft-tissue changes, were not included. Psychosocial factors and pain sensitization, which can influence pain perception, were not assessed. The study relied on patient-reported outcome measures, which are subject to recall bias and inter-individual variability.

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