Document Type : Original Article
Authors
1 Rheumatology and rehabilitation department, Faculty of medicine Al-Azhar university, Cairo, Egypt
2 Department of Rheumatology and Rehabilitation, Faculty of Medicine, Al-Azhar University, Cairo, Egypt.
3 Rheumatology and Rehabilitation Department, faculty of Medicine, AL-Azhar university, Cairo, Egypt
Abstract
Keywords
INTRODUCTION
Osteoarthritis (OA) represents a global health issue, with being the second source of disability 1.2. Moreover, it affects socioeconomic status negatively.3
Pain site detection is an efficient tool for diagnosing health issues and providing the best treatment4. OA influences physical impairment and pain severity, with recorded poor clinical outcomes5.
Photographic Knee Pain Map (PKPM) has been optimized to detect ten zones of pain sites with margins based on anatomic boundaries.6
This study aims to detect the pattern and site of knee pain in patients with knee OA confirmed by X-ray and their effect on the functional status.
PATIENTS AND METHODS
One hundred patients with primary knee OA have been included in this cross-sectional study. The participants have met the criteria of American College of Rheumatology (ACR) for OA diagnosis.7
They have been selected from the Rheumatology and Rehabilitation outpatient clinic, El-Hussein University Hospital. Patients with hip disorders, knee surgery, post-traumatic, and secondary knee OA have been excluded.
PKPM6 has been used to determine pain sites in most symptomatic knee based on anatomic landmarks in areas such as the posterior knee zone, tibia, patella tendon, medial and lateral patella, quadriceps tendon, superior medial and lateral zone, and lateral and medial joint line areas. Pain has been classified as absent or present in the previous zones.
Posterior-anterior (PA) and lateral views of knees have been obtained using plain X-rays. The Kallgren–Lawrence (K-L) radiograph score[i] has been used for scoring as follows: grade 2 represents possible joint space narrowing (JSN) and definite osteophytes. Grade 3 reflects possible bone deformity, definite JSN, and moderate multiple osteophytes. Grade 4 indicates definite bone deformity, severe sclerosis, marked JSN, and large osteophytes.
Physical function and experienced pain throughout daily activities have been evaluated by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The pain subscale ranges from zero (no pain) to four (severe pain), with an optimum score of 20. The physical function subscale ranges from zero (no physical dysfunction) to four (severe physical dysfunction), with an optimum score of 68.9
Statistical analysis
Statistical Package for Social Science version 16, Chicago, IL, USA (SPSS) has been used to gather, tabulate, and analyze data. Percentages and frequencies have been used to demonstrate qualitative data. Moreover, mean ± standard deviation has been used to represent quantitative data, with the significant results obtained at P values less than 0.05.
RESULTS
Table (1) shows the demographic characteristics of the studied patients. The mean age of the patients was 47.6 ± 6.3 years with a range of (35-62) years. Most patients were females (88%)
Table (2) shows the total WOMAC score, stiffness, and pain characteristics of the studied patients. Most patients had morning stiffness (79%) with a duration ranging from 5 to 20 minutes (mean 11.2± 5.7 minutes). The mean VAS for pain was 6.95± 0.97. The pain was ranged from moderate (29%) to severe (71%), with no patients experiencing mild pain. The mean total WOMAC score was 46.29± 13.03.
Figure (1) shows the right knee pain map of the studied patients. The most common site of pain was localized at the patella (41%), followed by medial joint pain (16%), and then diffuse knee pain (14%).
Figure (2) shows the left knee pain map of the studied patients. The most common site of pain was localized at the patella (25%), followed by diffuse knee pain (20%) and then localized inferior medial (6%) and medial region (6%).
Table (3) shows the WOMAC pain items of the studied patients. The mean walking pain, night pain and standing WOMAC for pain was ranged from moderate to severe (2-3). The mean WOMAC pain on upstairs was ranged from severe to extreme (3-4). The mean WOMAC resting pain was ranged from mild to moderate (1-2).
Table (4) shows the WOMAC stiffness items of the studied patients. The mean WOMAC for morning stiffness was ranged from mild to moderate (1-2). The mean WOMAC stiffness later the day was ranged from none to mild (0-1).
Table (5) shows the WOMAC physical function items of the studied patients. The most difficult function to perform was heavy domestic duties with a mean of 3.26±0.85 (severe to extreme 3-4), followed by going upstairs with a mean of 3.03±0.70 (severe to extreme 3-4) and then going downstairs, getting in and out of a car, and shopping with a mean of 2.6±0.92, 2.54±0.83, and 2.43±1.01 respectively (moderate to severe 2-3).
|
|
|
Total (n=100) |
|
|
Age |
Mean (SD) |
47.6 |
6.3 |
|
Range |
35 |
62 |
|
|
Gender |
Male (%) |
12 |
12.0 |
|
Female (%) |
88 |
88.0 |
|
|
Occupation |
Occupied (%) |
69 |
69.0 |
|
Housewives (%) |
31 |
31.0 |
|
SD: standard deviation
Table 1: Demographic characteristics of the studied patients (n=100)
|
|
|
Total (n=100) |
|
|
Morning stiffness |
Present (%) |
79 |
79.0 |
|
Absent (%) |
21 |
21.0 |
|
|
Stiffness duration (minutes) |
Mean (SD) |
11.2 |
5.7 |
|
Range |
5 |
20 |
|
|
Pain VAS |
Mean (SD) |
6.95 |
0.97 |
|
Range |
5 |
9 |
|
|
Pain severity |
Mild |
0 |
0.0 |
|
Moderate |
29 |
29.0 |
|
|
Severe |
71 |
71.0 |
|
|
Total WOMAC score |
Mean (SD) |
46.29 |
13.03 |
|
Range |
0 |
68 |
|
Table 2:WOMAC score, stiffness, and pain characteristics of the studied patients (n=100)
SD: standard deviation, VAS: visual analogue scale (0-10), 1–4 for mild pain, 5–6 for moderate pain, and 7–10 for severe pain, total WOMAC =0-96.
Fig. 1: Right knee pain map of the studied patient
Fig. 2: Left knee pain map of the studied patients
|
WOMAC pain items |
Total (n=100) |
|
|
Mean |
SD |
|
|
Walking pain |
2.45 |
1.09 |
|
Pain on upstairs |
3.27 |
0.67 |
|
Nocturnal (night) pain |
2.15 |
0.90 |
|
Rest (sitting) pain |
1.38 |
0.68 |
|
Weight-bearing (standing) pain |
2.78 |
1.03 |
|
Total WOMAC pain |
11.78 |
3.75 |
Table 3: WOMAC pain items (n=5) of the studied patients (n=100)
SD: standard deviation, the ordinal pain scale of every item: 0-4, the Likert scale for all items: none (0), mild (1), moderate (2), severe (3), and extreme (4), total pain=0-20.
|
WOMAC stiffness items |
Total (n=100) |
|
|
Mean |
SD |
|
|
Morning stiffness |
1.46 |
1.02 |
|
Stiffness later the day |
0.85 |
0.68 |
|
Total WOMAC stiffness |
2.26 |
1.66 |
Table 4: WOMAC stiffness items (n=2) of the studied patients (n=100)
SD: standard deviation, the ordinal pain scale of every item: 0-4, the Likert scale for all items: none (0), mild (1), moderate (2), severe (3), and extreme (4), total stiffness=0-8.
|
WOMAC function: difficulty with |
Total (n=100) |
|
|
Mean |
SD |
|
|
Going downstairs |
2.60 |
0.92 |
|
Going upstairs |
3.03 |
0.70 |
|
Arising from sitting |
1.83 |
0.59 |
|
Standing |
1.46 |
0.66 |
|
Bending |
1.52 |
0.58 |
|
Walking on flat ground |
1.56 |
0.54 |
|
Getting in and out of a car |
2.54 |
0.83 |
|
Shopping |
2.43 |
1.01 |
|
Taking off socks |
1.55 |
0.64 |
|
Lying down |
1.35 |
0.63 |
|
Putting on socks |
1.51 |
0.61 |
|
Arising from bed |
1.38 |
0.57 |
|
Getting in and out of the bath |
1.60 |
0.87 |
|
Sitting |
1.69 |
0.84 |
|
Getting on and off the toilet |
1.96 |
0.77 |
|
Heavy domestic duties |
3.26 |
0.85 |
|
Light domestic duties |
1.64 |
0.68 |
|
Total WOMAC function |
32.25 |
8.86 |
Table 5: WOMAC physical function items (n=17) of the studied patients (n=100)
SD: standard deviation, the ordinal pain scale of every item: 0-4, the Likert scale for all items: none (0), mild (1), moderate (2), severe (3), and extreme (4), total function=0-68.
DISCUSSION
This study aims to evaluate OA pain patterns and their relationship to physical function and pain severity.
Previous studies have concentrated on assessing the duration and frequency of knee pain, besides its location, and pattern via several techniques such as the knee diagram[ii].
Our study has shown that OA patients' ages have 35 to 62 years, with an average of 47.6 ± 6.3 years. Most patients have been females (88%). Thompson et al.5 have performed a similar study to evaluate the relationship between OA risk factors and the different types of knee pain. Most of the participants' ages have ranged from 45-64 years. Most of patients have been females (62%).
The mean VAS for pain has been 6.95± 0.97. The pain has ranged from moderate (29%) to severe (71%), with no patients experiencing mild pain. The mean WOMAC has been 46.29± 13.03.
McLendon et al.11 have shown that knee pain is more valuable in determining physical dysfunctions than radiographic characteristics of knee OA.
Zhang and Jordan12have illustrated how difficult it is to investigate risk variables for symptomatic OA. While OA pain has been regarded as chronic, it is not always persistent. Throughout the disease, physicians frequently find that patients with OA experience pain aggravation.
However, few studies have been performed to evaluate the association between risk variables and pain patterns due to methodological and practical challenges.
In our study, the WOMAC total pain score has been 12± 3.8. and Most of our patients (75%) have experienced severe WOMAC pain.
Similarly, Cubukcu et al.13 have reported that the WOMAC pain score (mean ± SD) is 14± 3.35, which indicates that most of their patients have experienced severe WOMAC pain.
In our results there was moderate correlation between VAS pain score and WOMAC pain score (r=0.472, p<0.0001).
Basaran et al.14 have performed a similar study to assess the reliability and validity of the WOMAC OA index and WOMAC has shown moderate correlation with VAS and his study concluded that WOMAC pain represents a consistent index to be used with OA patients.
Our study has reported that the mean WOMAC for morning stiffness ranges from mild to moderate (1-2). A remarkable association has been found between severe pain measured by VAS pain score and degree of stiffness measured by WOMAC stiffness (r=0.636, p<0.0001).
Our findings have revealed a positive correlation between severe pain measured by WOMAC pain score and the following: severe stiffness measured by WOMAC stiffness (r=0.357, p<0.0001). Physical impairment measured by WOMAC function (r=0.857, p<0.0001). Higher values of total WOMAC score (r=0.916, p<0.0001).
Similarly, Cubukcu et al.13 have documented that WOMAC pain scores are significantly associated with WOMAC disability (r=0.631, p<0.0001) and WOMAC stiffness (r=0.342, p<0.01).
Alkan et al.15 have performed a study to determine relationships between conventional clinical measures and self-reported disability. In OA patients, they have found that pain areas and physical function are significantly correlated with WOMAC subgroup scores and VAS pain (p < 0.05).
There have been significant correlations between severe pain measured by VAS pain score and severe difficulty in physical functions measured by WOMAC function (r=0.521, p<0.0001),
The likelihood of disability is increased in communities where knee pain is prevalent. Thus, it is critical to comprehend the elements that contribute to disability in patients with knee OA. Several studies have examined the association between pain and physical function in people with knee OA11.16.17
In line with these investigations, we have found a positive association between pain severity and disability using WOMAC subscales. The WOMAC scale has enabled an in-depth examination of pain. Patients have rated the severity of their pain while undertaking activities using the WOMAC pain subscale. We have interpreted this finding as the result of a vicious cycle of pain, causing decreased functional abilities.
According to our findings, most of patients hav been localized pain pattern (63%), consistent with Thompson et al.5, who have revealed that localized pain represented 50.6%, then regional (25.9 %), and diffuse pain (23.5%). The pain patterns in both knees have been consistent.
It is critical to detect the precise area of knee pain for diagnosis. It is unknown whether the site of knee pain varies naturally as the condition progresses.18.19
Sengupta et al.20 have compared pain emanating from the patellofemoral, lateral, and medial regions to osteophytes visible on magnetic resonance imaging scans.
Our results have revealed that there were significant correlations between severe pain measured by VAS pain score female sex (r=0.56, p<0.0001), as well as higher disease duration (r=0.303, p=0.01).
Moreover, there have been significant correlations between severe pain measured by WOMAC pain score and female sex (r=0.44, p<0.0001).
Females are more exposed to experience knee OA12, which may be due to differences in the pathophysiology. For instance, there may be alterations in cartilage and bone associated with differences in pain sensitivity between the two genders.
Fischbach and Jordan21have discovered that female sex is linked with decreased medial cartilage in OA patients using magnetic resonance imaging (MRI). However, variations in pain rating have not been investigated.
Functional MRI (fMRI) has demonstrated that gender variation is associated with activating pain sensation and processing centers such as the cerebellar cortex, hippocampus, dorsolateral prefrontal cortex, and mid-cingulate cortex.22
CONCLUSION
Majority of patients with knee OA had moderate level of knee pain and functional disability in daily living and they had the ability to localize site of pain. Also, the severity of knee pain and stiffness may influence the degree of disability in OA patients. As a result, OA treatments can be based on clinical aspects and functional status rather than relying on radiological findings.
[i] Kallgren JH and Lawrence JS. Radiological assessment of osteoarthrosis. Ann Rheum Dis. 1957; 16:494-502.
[ii] Hochberg MC, Lawrence RC, Everett DF, Cornoni HJ. Epidemiologic associations of pain in osteoarthritis of the knee: data from the National Health and Nutrition Examination Survey and the National Health and Nutrition Examination-I Epidemiologic Follow-up Survey. Semin Arthritis Rheum. 1989; 18(4 Suppl 2):4–9.
REFERENCES
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