Level of pain and physical function in patient with chronic knee pain visiting Dhulikhel hospital: A cross sectional study

Knee pain is one of the common causes of chronic pain mainly in the older adults.Chronic knee pain (CKP) is commonly due to arthritic changes (osteoarthritis). Chronic knee pain is a common and major health problem in ageing population. Knee pain is associated with high levels of disability. So early detection and treatment of pain related functional limitation is likely to have major inuence on healthy ageing. The general objective of this study was to quantify the level of pain and physical function in patient with CKP.


Results
75.6% of female with chronic knee pain was found with the average pain level found to be 5 in N-NPRS scale.Among them 80.8% of chronic knee pain was due to knee osteoarthritis. Sitting function was found to be affected in 82.1% of population with mean Nepali version of Patient speci c functional Scale score of 2. Similarly 80.8% reported going downstairs to be di cult due to knee pain with N-PSFS score of 2.

Conclusion
Pain and functional disability are the principle ndings in patient with chronic knee pain for which they seek medical treatment .So the treatments should target on functional task with effective strategy. addressing disability. Focus on function is important for the development of optimal rehabilitation programs in patients with chronic knee pain.

Background
Pain is de ned as unpleasant sensory or emotional disturbance that occurs due to actual or potential tissue damage [1].So the pain is considered to be chronic if the duration of pain is more than 3 month and pain prolongs past normal healing time and hence lack the acute warning function of the physiological nociception [2,3]. There are seven classi cation of chronic pain where chronic knee pain falls mainly under chronic musculoskeletal pain [3].Knee pain is one of the common causes of chronic pain mainly in the older adults [3,4].
In a study done in the community dwelling adults of Iran, the prevalence of chronic knee pain was found to be 29.97% [5].Chronic knee pain is commonly due to arthritic change and knee osteoarthritis is one of the leading cause of chronic knee pain [6]. The patellofemoral pain syndrome is one of the leading causes of pain in adults and adolescents [7].Since knee is one of the largest weight bearing joint in our body, it is always prone to overload and overuse causing pain and limiting the lower limb function [8]. Usually the mechanical axis passes through or just medial to the centre of the knee joint in the coronal plane [9].
Deviation of the mechanical axis away from this leads to increased contact stresses at the joint surface.
Mainly during maximum knee exion of 20 degree, the patellofemoral compressive force is approximately 25 to 50 % of body weight [9]. The consequence of the altered biomechanics of the knee leads to chronic symptoms [10].People with knee pain have 5 fold raise in risk of worst lower extremity function compared to people without knee pain [12]. Chronic knee pain is associated with functional impairment and this will cause social isolation [12,13]. In a study prevalence of chronic knee pain was found to be 12.1% [14]. Most of the participants in the study were not able to go uphill and downhill.
Chronic knee pain is a major health problem and is also very common in ageing population [14].Kneeling, squatting on the toilet, carrying heavy weights, getting on and off the toilet, were the activities that had the greatest proportion of participants reporting knee pain [14].Knee pain is associated with high levels of disability [9]. So early treatment of pain related functional limitation is likely to have major in uence on healthy ageing for adult with chronic knee pain.Functional exercises are regarded in rehabilitation to restore good knee function [12,13].
Pain is the main complain of people living with osteoarthritis and they are distressed mainly because of its impact on their physical function [15,16]. Identi cation of the key impairments related to pain and function may assist in delineating physical therapy treatment approaches for patients with PFPS. If it can be shown that particular impairments are associated with function and pain, targeting such impairments may improve the effectiveness of physical therapy for patients with PFPS [17].The exercise that will improve the physical factors will be based on functional exercise [18]. A home based program based on functional exercises and the management of kinesiophobia was useful in changing the course of disability, fear-avoidance beliefs, pain, and the quality of life in patients with TKA [19].

Study type and design
A cross sectional study was designed as the study aimed to determine the level of pain and function with the demographic characteristics of people with chronic knee pain Place and duration of study Dhulikhel Hospital: Physiotherapy outpatient department and orthopedic outpatient department.It is an excellent site for data collection as it receives patients with knee pain from both rural and urban communities with different ethnicity and background making the sample more representative. The data was collected within 2 weeks of times and the study was done within 6 month of time.
Sample size and sampling method A total of 78 participants was recruited after calculating sample size for non probability convenience sampling method for this study

Methods of data collection
Individuals with chronic knee pain and who show willingness to participate in the study were screened for the eligibility criteria. After screening, participants who were eligible were provided with a subjective information sheet. The participants were provided with demographic form with N-NPRS and N-PSFS questionnaire to ll up which took 3.5 to 5 minutes to complete. The data was collected, recorded and analyzed using Statistical Package for the Social Sciences (SPSS) version 23.

Ethical approval and consent
This research was conducted after the approval from Institutional Review Committee, Kathmandu University School of Medical Sciences considering the guidelines to conduct research given by Declaration of Helsinki. Written informed consent was obtained from all participants prior to data collection. Verbal consent was obtained if the participants could not sign, and a witness signed on their behalf. We used Nepali version of numerical pain rating scale and Nepali version of patient speci c functional scale. NPRS is routinely used outcome measure for accessing the pain intensity in daily clinical practice. Out of many versions, the 11 point NPRS is most commonly preferred. It has acceptable psychometric properties. One of the main advantages of NPRS is that it can be used by people with low level of literacy as well and is routinely used in many countries and languages. NPRS-NP showed excellent test-retest reliability and a MDC of 1.13 points. NPRS-NP demonstrated a good construct validity The anchor on the left side corresponds to "no pain" that is zero and the anchor at the right side corresponds to the "worst possible pain" or "maximum pain". It was administered by patient self-report and by face to face interview [25,26].Patient speci c functional scale is a patient reported outcome measure in which patient themselves identi es the activity that are most important to them and rate them in a scale of 0 to 10 where higher score shows the better physical function. The proposed advantages of the PSFS include its wide applicability and ease of use clinically. PSFS-NP showed good reliability with Cronbach's alpha = 0.75; ICC = 0.89.Self-reported di culty in function using scale from the questionnaire was done in our study [27].

Results
Data were collected from the 78 participants. Descriptive statistics of the demographic characteristics, knee pain results and PSFS-NPRS ndings are illustrated in table I, II and III respectively. Similarly, distribution by PSFS ndings is depicted in Fig. 1.
The mean age of the patient was 52.59 ± 14.98 years.75.6% of the participants with chronic knee pain were female. Among 78 participants 80.8% of them were illiterate and 46.2% of them were farmers. Newar community patients were more i.e. 37.2%. Chronic knee pain was found to be more in illiterate female patients who were mostly farmer.Knee OA was the main cause of Chronic Knee pain followed by patella femoral pain syndrome. Bilateral knee pain was found to be prevalent in 59% of the patient with mean duration of 20 month. Table III shows about the functional level of the population where sitting function was found to be affected in 82.1% of population with mean PSFS score of 2. Similarly carrying load was found to be the most di cult task with PSFS score of 1. Mean pain level of patient with chronic knee pain in numerical pain rating scale was 5 with maximum score of 7 and minimum score of 2.

Discussion
The study shows sitting function was mostly affected in 82.1% of population with mean PSFS score of 2. Similarly carrying load was the most di cult task with mean PSFS score of 1. 80.8% of them reported going downstairs to be di cult due to knee pain with PSFS score of 2. Going upstairs was found to be di cult for 74.4% with PSFS score of 3. Mean pain level of patient with chronic knee pain in Nepali version of Numerical Pain Rating scale was 5 with maximum NPRS score7 and minimum score of 2.0. The main cause of chronic knee pain in following study shows knee osteoarthritis which is consistent with the similar study that has been done in Iran [5].
To the best of our knowledge no prior study has been done about pain level in chronic knee pain using the NPRS scale; thus a direct comparison of present ndings with the other studies couldn't be made. One study reported the baseline score of pain of people with Knee osteoarthritis to be 5.9 in Numerical rating scale which is expressed in a scale of 0 to 10 [10]. Combination of tibio-femoral and patello-femoral pain was associated with greater self-reported pain.The difference in pain between individual can be due to risk factors like age and gender [12]. There are studies suggesting that the psychological factors and the structural damage to the surrounding structures were the leading causes of pain [13]. Although this study didn't considered the level of pain during rest or movement, the rest pain in previous study shows 2 in VAS and 7 with the movement [29].
It may be argued that the speci c site of cartilage destruction within a joint might explain the presence of pain at rest and/or movement [29]. CKP was found to be more in female patients than in the male patients in the present study which is consistent with a study that has been done in Japan. This type of nding warrants the sex speci c preventive measures and management of chronic knee pain [30]. It is necessary to focus on the functional consequence which is important because knowledge of functional consequences is essential for development of optimal rehabilitation programs inpatient with CKP. [32] Limitation of the study First the study is a cross sectional study design so no casual conclusions can be drawn from the study results. Secondly, the association of pain and function was not analyzed. Psychological variables and health related beliefs are important determinants of functioning which was not analyzed in this study which is another potential limitation of the study.

Conclusion
Pain and functional limitation was main nding among the population with chronic knee pain. Regarding function, sitting function was mainly hampered. Along with this sit to stand, walking in upstairs and downstairs were also signi cantly affected. Knee osteoarthritis was the main cause of CKP. Proper functional rehabilitation protocol is necessary for such population .Olderage group was found with more pain as well as functional problem. So the functional rehabilitation should have focus on the older age group.To conclude knowledge of functional consequences is essential for development of optimal rehabilitation programs inpatient with CKP. Identi cation of the key impairments related to pain and function may assist in delineating physical therapy treatment approaches for patients with CKP.     Distribution by PSFS score