Intra-articular injection of platelet-rich plasma and therapeutic exercise in knee osteoarthritis

Context There is no definite treatment strategy capable of decreasing destruction of cartilage and enhancing its healing. Intra-articular injection of platelet-rich plasma (PRP) provides a lot of growth factors that are capable of stimulating regeneration of cartilage and is supposed to be a future solution to patients with osteoarthritis (OA). Aim To detect the efficacy of intra-articular injection of PRP or therapeutic exercise (Ex) alone as well as a combination of both in the treatment of idiopathic knee OA. Settings and design A prospective randomized controlled clinical study was conducted. Patients and methods A total of 60 patients, 44 to 65 years of age, having idiopathic unilateral knee OA were included in the study and were divided into three groups: PRP group included 20 patients and were treated with intra-articular PRP injection, Ex group included 20 patients and were treated with only therapeutic Ex, and PRP and Ex group included 20 patients who were treated with both PRP intra-articular injection and therapeutic Ex. Evaluation of all patients was done by visual analogue scale, tenderness, range of motion, thigh circumference, and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores at baseline and 1 and 6 months later. Objective evaluation was done through MRI of osteoarthritic knee at baseline and 6 months later. Statistical analysis Statistical analyses were performed using SPSS for windows, version 20.0. Results Baseline WOMAC score differences among the three groups were not statistically significant but were significant 6 months after treatment. In PRP and Ex groups, there was a significant improvement after treatment, whereas a highly significant improvement in PRP+Ex group. MRI grading differences among the three groups were not significant before or after treatment, with no improvement in all three groups after treatment. Conclusion A combination of intra-articular injection of PRP and therapeutic Ex resulted in significantly lesser visual analogue scale, WOMAC score, and joint tenderness compared with PRP or Ex alone.


Introduction
Knee osteoarthritis (OA) is the most common OA condition and is the most common cause of impaired mobility and disability in the elderly [1]. OA is associated with destruction of articular cartilage, which is progressive, and is partly owing to increased destruction and decreased production of proteoglycans, the main component of articular cartilage [2]. Besides, OA affects the subchondral bone, capsule, ligaments, synovial membrane, tendons, and even peri-articular muscles because of limitation of mobility, leading to their weakness, which act as an aggravating factor for the disease [3]. Various treatments, such as NSAIDs, hyaluronic acid (HA), chondroitin sulfate, glucocorticoids, and glucosamine, have been used as ways for treatment of pain and disability, with varying rates of success [4]. These agents have not been shown to be effective clearly, and owing to the defect in the common accepted evidence, they are not ideal solutions for the treatment of OA [5]. The American College of Rheumatology (ACR) subcommittee on OA recommends corticosteroid injections collectively as effective ways for decreasing joint pain. However, American Society of Orthopaedic Surgeons have been incapable of suggesting for or against the intra-articular injection of corticosteroids in their recommendations [6]. Corticosteroid injections are often thought of as an associate adjunct to main treatment for management of cases with moderate to severe OA owing to its role in short-term pain relief [7].
In OA, inflammation results in a high permeable synovial membrane for HA. The increased levels of cytokines, proteolytic enzymes, and free radicals in the synovial membrane impair HA function and decrease its concentration, eventually leading to deterioration of OA. So, the intra-articular injection of HA restores normal visco-elastic properties of synovial fluid (SF). HA has beneficial effects such as protecting cartilage against erosion and promoting the intra-articular HA secretion. To sum up, the application of HA injections is safe and may be effective for reduction of pain in mild knee OA up to 24 weeks. However, cost should be taken in consideration before injection of HA in osteoarthritic knee [8]. The ACR does not recommend for the use of injection of HA in knee OA [6]. Moreover, American Society of Orthopedic Surgeons has no recommendations for the utilization of intra-articular HA. A study by Ayhan et al. [9] supports strong evidence of recommendation against the utilization of intra-articular HA in their guideline.
The role of exercise (Ex) in the treatment of knee OA has been acknowledged. According to recommendations by ACR regarding knee OA [6] and OA Research Society International [10], Ex therapy is one of the effective methods for knee OA management. Ex reduces pain and improves the joint range of motion and muscle strength [11].
Another line of treatment of knee OA is platelet-rich plasma (PRP). It is a biological autologous management option obtained from patients' own plasma, which contains a high concentration of growth factors (GFs) that are platelet-derived growth factor such as insulinlike growth factor-1, transforming growth factor-beta, epidermal growth factor (EGF), and vascular endothelial growth factor [12]. All the GFs may lead to healing of soft tissue and regeneration of bone by the increased physiologic secretion of platelet-derived factors at the management site directly [13,14].
PRP is one of the options in the management of knee OA [15]; however, its effectiveness and wide application is still controversial [16]. Although good results were reported about PRP in knee OA, most studies are based on subjective data and use only questionnaires for evaluation of patients [15]. Therefore, studies based on objective data as MRI evaluation of patients after PRP injections are needed in this regard.
So in this research work, we prepared PRP and used the preparation for intra-articular injection; moreover, an Ex program was also applied. We used both methods to find their efficacy in the improvement of knee OA. Besides, the results were evaluated objectively using MRI before and after treatment.

Aim
The aim was to detect the efficacy of intra-articular injection of PRP alone, therapeutic Ex alone, and combination of both in the treatment of idiopathic knee OA. Exclusion criteria [17] The following were the exclusion criteria:

Patients and methods
(1) Patients with secondary OA or inflammatory arthritis.

Methods
All patients gave consent and were subjected to the following: (1) Detailed history taking.
(2) Pain assessment by pain visual analogue scale (VAS): VAS of pain is a one-dimensional tool to measure pain severity. It is 10-cm transverse line that is marked every 1 cm, and pain severity range from 0 to 10 (0 reflects no pain at the left end of horizontal line and 10 reflects worst pain at the right end of the line) [19]. Patients stated their severity of pain during the past 4 weeks. (i) Swelling (localized or diffuse, bony prominence, or synovial thickening). (ii) Tenderness was evaluated on a rating scale 0-3: [20] Grade 0: there is no tenderness.  (c) Subchondral cyst more than 10 mm. (iv) Grade 3: cartilage injury grade III with at least one of the following: (a) Osteophyte more than 5 mm. (b) Bone marrow edema more than 10 mm. (c) Subchondral cyst more than 10 mm.

Pre-injection precautions published by American
Academy of Orthopaedic Surgeons are as follows: [27] (a) No corticosteroid medications for 2-3 weeks before the injection. (b) Stop taking NSAID 1 week before the injection. (c) No anticoagulation medication 5 days before the injection. Injection procedure [28] :Vein puncture and subsequent collection of 10 cm 3 of venous blood into a tube containing an anticoagulant (sterile sodium citrated tubes) were done by 10 ml syringe with needle bore of 21 G. The tube with citrated blood was exposed to double spin technique. First centrifugation (the used device was manufactured by dragon labs company and the model was DMO 412) was at 1600 rpm for 15 min, resulting into three layers: the lower layer is made of red blood cells, intermediate layer is formed of white blood cells, and the upper one is formed of plasma. The upper two layers were then collected in plain tube, and second centrifuged at 3500 rpm was done for another 10 min to yield two layers: the superficial layer is platelet-poor layer, which was withdrawn, leaving the concentrate of platelets at the bottom (second layer), for obtaining more concentrated platelet layer (PRP) [15]. The patient was asked to relax in the supine position during the injection for facilitation and for making it less painful. Skin of injection site was disinfected by betadine. Then a 3 cm 3 of PRP by 5 ml syringe with 21 G needl was injected in a sterile place at the anteromedial part of the knee joint in flexed knee position.
The patient was then asked after 15 min to move his/her knee actively in flexion and extension, so that PRP unfolds across the joint area [15]. The patient was then discharged. Postinjection precautions were as follows [15]: The following muscle groups will be gradually trained: quadriceps, hamstrings, and calf muscles [29].
The following six Exs (three strengthening and three stretching) were recommended [29,30]:

Statistical analysis
The collected data were summarized, tabulated, and analyzed using the SPSS (version 20.0; SPSS, Chicago, Illinois, USA) program for statistical analysis. The appropriate statistical test was used to analyze the data. The level of significance was considered at P value less than or equal to 0.05 and high significance at P value less than or equal to 0.001.

Results
This study included 60 patients having unilateral OA of the knee joint. Ex, exercise; PRP, platelet-rich plasma; VAS, visual analogue scale. P 1 , comparison between baseline value and 1 month after treatment for each group. P 2 , comparison between baseline value and 6 months after treatment for each group. P 3 , comparison between Ex group and PRP group. P 4 , comparison between Ex group and Ex+PRP group. P 5 , comparison between PRP group and Ex+PRP group. *P value less than 0.05, significant. **P value less than 0.001, highly significant. insignificant difference among the three groups. One and 6 months after treatment, the group treated with combination of Ex and PRP showed more significant improvement of thigh circumference than the other two groups. Compared with the PRP group, the Ex group had a greater improvement of thigh circumference, as shown in Table 5.
There was an insignificant difference between baseline and 6-month post-treatment MRI grading in Ex, PRP, and Ex+PRP groups, as shown in Table 6.
There was an insignificant improvement of effusion in Ex and PRP groups but significant in Ex+PRP group as shown in Table 7.

Discussion
OA of the knee is a chronic disease associated with pain and morbidity. The increasing number of patients with  Ex, exercise; PRP, platelet-rich plasma. *P value less than 0.05, significant. **P value less than 0.001, highly significant. symptomatic OA will continue to place an increasingly large economic burden on global health care systems [31].
The various agents for treatment of OA have not been showed to be effective clearly, and owing to the defect in commonly accepted evidence, there may not be ideal solutions for the treatment of OA [5]. This has led to the emergence of other options for functional improvement and symptom relief in these patients [32].
Although there are a good amount of studies documenting the use of HA in the management of knee OA, there are limited studies documenting the use of PRP. More importantly, there are no studies comparing the utilization of PRP with Ex in the management of knee OA [33].
However, strong proof from elegant clinical trials to support PRP utilization for OA of the knee joint continues to be little [34]. Therefore, PRP requires more investigation to assess its effectiveness in the intra-articular injection [35].
According to the recommendations by ACR about knee OA [6] and OA Research Society International [10], Ex therapy is one of the effective methods for knee OA management. Light to moderate intensity Ex has been shown to positively influence knee OA [36]. In a study done in 2015, Nejati et al. [37] demonstrated that Ex for muscles around knee can promote the efficacy of different therapeutic interventions for knee OA.
PRP decreases pain and has anti-inflammatory effect and Ex has anti-inflammatory effect. Thus, an additional result, in treating knee OA, could be obtained from this combination [37].
To our information, this is the first study that evaluates the combination of PRP intra-articular injection treatment and therapeutic Ex in treatment of idiopathic knee OA.
The aim of this study was to compare the efficacy of intra-articular injection of PRP alone, therapeutic Ex alone, and combination of both in the treatment of idiopathic knee OA.
In our study, there was a significant improvement in all evaluation scores (VAS, tenderness, and WOMAC) after treatment at 1or 6 months. Moreover, there was a significant difference between these scores among the three groups after management either after 1or 6 months, with improvement in PRP group more than Ex group and in PRP+Ex group more than the other two groups.
The result of PRP group was in agreement with many studies that used PRP for the treatment of OA [14,34,[38][39][40][41]. It was demonstrated that there was an improvement in VAS and all WOMAC parameters, pain scores, and clinical and functional scores after PRP and supported that intra-articular PRP injections had a better response in younger patients, more active patients, and those with Ex, exercise; PRP, platelet-rich plasma. *P value less than 0.05, significant. **P value less than 0.001, highly significant. low-grade OA [14,38]. In a study done in 2013, 78 patients (156 knees) had bilateral knee OA, and patients were administered two PRP injections 3 weeks apart. PRP was effective in alleviating symptoms and lowering scores of WOMAC and VAS. The results, however, deteriorated after 6 months [34]. The result of Ex group was in agreement with many studies [37,42,43]. The mechanisms underlying beneficial effects of Ex are largely unknown [44].
Ex for persons with knee OA results in small-tomoderate improvements in function and pain. In spite of the variability in results and inherent biases in trials, Ex seems to decrease pain and enhance function for the persons with knee OA [42].
There is overwhelming proof that light to moderate physical activity does not lead to knee OA or even accelerate the condition. In fact, Ex could stop its onset and is clearly effective in the management of the pain and functional decline associated with OA. Health care providers should not hesitate to include recommendations for Ex as part of the clinical management of knee OA [43].
Nejati et al. [37] observed that the patients with knee OA and treated with Ex only had significant improvement in pain, walking, disability, sit-up speed, and stair climbing after treatment when compared with non-Ex group, with significant difference in VAS between the groups. The result of PRP+Ex group reflected the importance of Ex combination with PRP, which significantly reduced the OA symptoms and improved quality of life in these patients. This combination effect could also be owing to the nature of the OA disease and its effect on tissues and structures within the whole joint. So, this combination of PRP therapy and Ex holds promise for pain and inflammation relief, resulting in a reduction in medications. Moreover, in our study, there was a significant difference of knee flexion limitation and thigh circumference after management among the three groups either after 1or 6 months, but improvement in Ex group was more than PRP group and in PRP+Ex group was more than the other two groups. In all groups, there was a significant improvement after treatment in all scores either after 1 or 6 months. The result of PRP group was in agreement with a study done in 2015 [40] which showed significant improvement 6 months after PRP injection. The result of Ex group was in agreement with another study done in 2012 [45]. The results of PRP+Ex group also reflect the importance of Ex combination with PRP, which significantly reduce the OA symptoms. Flexion limitation and thigh circumference were improved with Ex than PRP. This result may be owing to that therapeutic Ex would effectively target these specific deficits [45]. In this study, there was a statistically significant improvement in all previous parameters after 1 and 6 months, with nearly same result at the 6-month follow-up, which is in agreement with the study by Maheshwari and Harshwardhan. This may reflect sustained effect for 6 months [41]. A number of approaches to OA management have failed to restore normal knee function and anatomy, or to slow the progression of OA [46]. PRP has been proposed to improve clinical and structural outcomes by delivering a high concentration of GFs that mediate remodeling. MRI is suitable for searching about this point [47]. Some theories have been proposed to clarify the mechanism by which PRP improves cartilage healing, such as PRP augments the secretion of HA, which has been observed in the presence of PRP [48]. Besides, the exposed osteoarthritic chondrocytes to PRP demonstrated less interleukin-1β which resulted in inhibition of collagen 2 and aggrecan gene expression, and diminished nuclear factor-B activation. These factors are considered as pathways involved in OA pathogenesis [49]. In an ovine model, a proliferation of autologous chondrocytes and mesenchymal stem cells was demonstrated after PRP exposure [50]. In this study, the baseline MRI demonstrated that most patient in all groups had grade 1 or 2 (nearly equal), with only four from 60 patients had grade 3, without significant differences between the groups. The difference among groups after treatment was insignificant. There were also insignificant differences between baseline and posttreatment MRI grading in Ex, PRP, and PRP+Ex groups. This result goes with a study done in 2013 by Halpern and his colleagues, who evaluated 22 patients defined anatomically by degeneration of articular cartilage and subchondral bone. This degeneration involved the lateral, medial, or patellofemoral compartments of the knee with Kellgren and Lawrence grading 0-4 of radiograph, confirmed by a baseline MRI and treated with a single PRP injection. The patients underwent clinical assessments by WOMAC score. There was a significant improvement of WOMAC scores, with a decrease of 41.7% (P=0.003) after 6 months. However, there was no change in the appearance of OA in 83.3% of all cases by MRI after 1 year when compared with baseline [28].So, the role of PRP in the cartilage repair is a matter of debate. The small sample of this study and other few studies that use MRI push us for further researches to fully comprehend the long-term clinical significance of MRI changes seen after PRP therapy. Ex may be sufficient in reducing pain and functional limitation, but they may not be adequate for the cartilage repair or even minimizing the rates of disease progression [51].
There was an improvement in effusion detected by MRI in PRP group and significant in PRP+Ex group after treatment. This reflected a combination effect of PRP and Ex. This result was in agreement with a study done in 2015 [40].

Conclusion
This study suggested that PRP and Ex may play a role in improving clinical outcomes in patients with knee OA in agreement with most of studies, but combination of PRP and Ex was better than PRP and Ex alone, which reflects the additive effects of both. However, it seemed to be noneffective in the repair process or disease progression.

Recommendation
From this study, we recommend the combination of PRP and Ex in the treatment of idiopathic knee OA. This combination therapy is considered safe and may result in improvement of resistant cases to traditional lines of treatment. The response can be sustained for a period up to 6 months.
Further studies may be required to optimize PRP or Ex prescription and to determine the best way to use them.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.