Efficacy of combined ozone and platelet-rich-plasma treatment versus platelet-rich-plasma treatment alone in early stage knee osteoarthritis

Abstract

BACKGROUND:

Osteoarthritis (OA) is a chronic disease most often occurring in knee joints, leading to pain of varying severity and deterioration in daily living activities.

OBJECTIVE:

To compare efficacy of platelet-rich-plasma (PRP) versus PRP in combination with ozone gas injection in patients with early stage knee OA.

METHODS:

Retrospective data of patients who received PRP alone ( $n=$ 45) or combined treatment (PRP $+$ ozone, $n=$ 35) injection was analyzed. Patients were evaluated using the visual analogue scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores.

RESULTS:

In both PRP alone and combined treatment groups, post-treatment VAS and WOMAC scores at month 1, month 3, and month 6 showed a significant reduction compared to pre-treatment scores ( $p<$ 0.001). Physical function and total WOMAC scores as well as VAS scores at post-treatment month 3 were significantly lower in the combined treatment group compared to the PRP alone group. Moreover, in the combined treatment group, VAS scores on Day 10 and hyper-inflammation at the injection site was significantly lower than the PRP alone group.

CONCLUSION:

In general, similar efficacy was observed between treatment with PRP alone and treatment with PRP in combination with ozone. However, patients receiving ozone treatment are less likely to experience post-injection pain and are more likely to recover faster when compared to patients receiving PRP treatment alone.

Keywords

Platelet-rich-plasma ozone knee osteoarthritis

1. Introduction

Osteoarthritis (OA) is a chronic disease most often occurring in knee joints, leading to pain of varying severity and deterioration in daily living activities [1]. Osteoarthritis affects approximately 250 million people worldwide and can lead to serious economic adverse effects as well as poor quality of life [2]. Oral medical therapy, several physical therapy modalities, and exercises as well as various injections such as steroids and hyaluronic acid are used for the treatment of knee OA. Surgical procedures are performed on patients who do not benefit from such therapies. However, no definitive treatment is available with any methods used for the treatment of knee OA. This led the investigators to conduct several trials for using different methods in knee OA treatment. Platelet-rich plasma (PRP) has been used for various maxillofacial and dermatological disorders since the 1950s [3, 4]. Recently, PRP has been used widely in musculoskeletal disorders for many reasons, including production from the patient’s own blood, higher efficacy, and fewer adverse effects [5, 6]. The PRP procedure includes administration of platelets derived from the patient’s blood and growth factors derived from these platelets to the pathological area [5, 6]. Platelets are concentrated by plasmapheresis and anticoagulated blood is separated into its’ solid and liquid components by two-phase centrifugation. In the last phase, plasma and platelets are separated from erythrocytes and leukocytes. Platelet-rich-plasma includes white blood cells and some proteins as well as platelets [7]. Neutrophils and monocytes may induce localized anti-inflammatory effects, which can accelerate tissue regeneration. Tissue regeneration is a complex process consisting of several phases such as chemotaxis, angiogenesis, cell proliferation, and matrix formation. Platelets promote these phases by the release of growth factors such as platelet-derived growth factor, vascular endothelial growth factor (VEGF), endothelial cell growth factor and fibroblast growth factor. Besides, transforming growth factor beta (TGF- $\beta$ ), which is a protein also released by the platelets, may demonstrate inhibitory effects on tissue regeneration and cause unpredictable results [8]. Using PRP treatment, disease progression can be controlled and a positive impact on healing of the affected joint can be obtained [7].

Ozone injection is another method used for injection. The effects of ozone were discovered in mid-19 ${}^{\text{th}}$ century. Ozone is an unstable molecule formed by the combination of oxygen atoms. The therapeutic effects of ozone include anti-inflammatory effects, positive impact on cellular metabolism following increased use of glucose, improvement of protein metabolism, conversion of unsaturated fatty acids into water-soluble compounds and improvement of erythrocyte activity [9]. There are publications supporting the use of ozone injection in knee OA treatment [10]. Ozone gas combined with oxygen gas is administered to the pathological area. Oxygen-ozone injection improves tissue oxygenation and inhibits inflammatory mediators such as TNF alpha. Ozone can also induce moderate oxidative stress and inhibit inflammatory responses. Ozone also has moderate analgesic effects through phosphodiesterase A2 blockage [11]. Several trials provided results confirming that ozone injection was safely used in treatment of lumbosacral disc herniation, post-laminectomy syndrome, and shoulder disorders [12, 13]. Moreover, ozone treatment was shown to be an efficient treatment method for managing symptoms after traumatic meniscal injuries [14].

Both PRP and ozone have recently gained popularity in the treatment of knee OA. Although similar in efficacy, ozone is also used for PRP activation. Currently there are not many studies comparing efficacy between PRP and PRP $+$ ozone treatments. In the published literature, there’s only one similar retrospective study conducted by Sabanci et al. [15] which evaluated the efficacy of PRP treatment combined with ozone. However Sabanci et al. [15] did not compare PRP treatment alone to combination treatment. Instead, they compared different doses of combination treatments. This is the first comparative study in which the objective was to evaluate the difference in efficacy between the pain and functional status of patients diagnosed with knee OA, who received PRP treatment alone compared to PRP treatment in combination with ozone.

2. Methods

Data from patients undergoing magnetic resonance imaging in combination with X-ray for evaluation of intra-articular problems in the outpatient clinic were assessed. The diagnosis of knee OA was made on the basis of the results of clinical examination and anteroposterior standing radiography. Among these, patients diagnosed with knee OA, who received PRP alone or PRP in combination with ozone injection (combined treatment) between 2016 and 2017 were included in the study. All patients included in the study were stage I or II according to the Kellgren-Lawrence grading. PRP treatment outcomes may be different in early and late stage OA. In order to have a homogenous patient population and to minimize bias, patients with early stage OA were preferred in this study [16]. Patients with bleeding disorders, pregnant women and patients with history of rheumatoid diseases or cancer were not included into the study. A total of 183 patients with knee OA were screened and 103 patients were excluded due to various reasons such as late stage OA or loss to follow-up. Among remaining 80 patients, 45 patients received PRP alone and 35 patients received combined PRP $+$ ozone injections. Patients who discontinued the PRP or ozone treatment were considered as drop-out patients (Fig. 1). Both groups received injections twice monthly.

Figure 1.

Disposition of patients.

For PRP administration, the Easy PRP Kit ${}^{\@setsize{\scriptsize}{8pt}{\viipt}{\@viipt}\textregistered}$ was centrifuged for five minutes at 1200 RCF. Afterward, the blood was separated into plasma and red blood cells (RBCs). Next, RBCs, which were collected in the RBC collector section, were discarded from the device. In order to concentrate platelets, a second centrifuge process was performed for 10 minutes at 1200 RCF. The final product was 1–3 ml of PRP containing leucocytes. An exogenous factor was not used for the process of activation, but allowing the platelets to be in direct contact with the joint collagen helped the activation. The injection site was prepared, a local anesthetic injection was administered, and the PRP was injected under sterile conditions using a 22G needle with the classic approach for intra-articular knee injections. For each patient, the anesthetic injection consisted of 2 cc of a mixture of 0.5 cc lidocaine and 5 cc of physiological serum.

For PRP and ozone group, PRP was prepared with the same kit as described above. Immediately after PRP administration, while the needle was still in the knee, approximately 3 cc of ozone gas (20 gamma, modular dose) was administered with the same injector tip.

All patients were evaluated before injection using special forms for specific diseases. Parameters such as weight, height, body mass index, age, gender and grade of knee OA were recorded. The visual analogue scale (VAS) for general pain and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale for functional status in OA were being used as a routine practice in the clinic.

For pain assessment with VAS, patients were asked to put a mark on a 10 cm line. The score was obtained by measuring the distance with a ruler on the line between the “no pain” anchor and the patient’s mark. Scores ranged from 0–100, higher score indicating greater pain intensity.

The WOMAC assessment is widely used in the evaluation of knee OA. It is a self-administered questionnaire consisting of 24 items divided into 3 subscales (pain, stiffness and physical function). The questionnaire provides a score between 0 and 100 points and lower scores indicate better knee status. WOMAC questions are scored on a scale of 0–4 (0 $=$ no pain/restriction, 1 $=$ mild pain/restriction, 2 $=$ moderate pain/restriction, 3 $=$ severe pain/restriction, 4 $=$ very severe pain/restriction) [17].

For each patient undergoing an intraarticular administration, evaluations with VAS and WOMAC were being conducted before treatment and 1, 3, 6 months after the treatment as a routine practice. For evaluation of complications, additional VAS evaluations for pain and examination for hyper-inflammation were performed 10 days after the first injection.

The injections were performed in all patients in the supine position. The skin of the injection site was prepared and draped. The PRP, or PRP + ozone injections were administered under sterile conditions using a needle through the classic suprapatellar approach for intraarticular injection.

Table 1

Demographics and patient characteristics

	(Mean $\pm$ SD/ $n$ – %)	(Median)	(Mean $\pm$ SD/ $n$ – %)	(Median)	$p$
	PRP treatment		PRP $+$ Ozone treatment
Age	58.6 $\pm$ 6.4	59.0	56.4 $\pm$ 9.3	52.0	0.146 ${}^{\text{a}}$
Gender
Female	42 93%		28 80%		0.074 ${}^{\text{b}}$
Male	3 7%		7 20%
Side
Right	9 20%		13 37%
Left	17 38%		15 43%		0.079 ${}^{\text{b}}$
Bilateral	19 42%		7 20%

${}^{\text{a}}$ : Mann-Whitney U test, ${}^{\text{b}}$ : Chi-square test, PRP: Platelet-rich-plasma, SD: Standard deviation.

This study was conducted in a retrospective manner, therefore a study specific formal consent was not obtained. However all patients signed an informed consent form which is being used in the clinic on a regular basis for all types of intraarticular injections. The study was approved by the Local Ethics Committee, Istanbul Kanuni Sultan Suleyman Education and Research Hospital, Turkey (ID Number: 2014/2-18129).

Descriptive statistics of the data were given as mean, standard deviation, median, minimum, maximum, frequency, and percentage. Independent quantitative data were analyzed with Mann-Whitney U test and dependent quantitative data was analyzed with the paired Friedman test (Wilcoxon test). Independent qualitative data were analyzed with the chi-square test. All statistical analysis was performed using SPSS software (IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, IBM Corp., NY, USA).

3. Results

There were no significant ( $p>$ 0.05) differences between PRP group and the PRP $+$ ozone group in terms of age, gender distribution and affected side (Table 1).

Within the same group, all evaluations were compared to pre-treatment. For both groups, all WOMAC subscale scores (pain, stiffness and physical function) including the WOMAC total score, as well as VAS scores, indicated a significant reduction when compared to pre-treatment ( $p<$ 0.001).

For WOMAC pain scores, there was no significant difference between two groups starting from pre-treatment to 6 ${}^{\text{th}}$ month visit ( $p>$ 0.05).

For WOMAC stiffness scores, no significant difference was observed between PRP alone and combined treatment groups in pre-treatment, 1 ${}^{\text{st}}$ and 3 ${}^{\text{rd}}$ month visits ( $p>$ 0.05 for all three visits). However, a statistically significant difference was observed between two groups on the 6 ${}^{\text{th}}$ month visit in terms of stiffness. On the 6 ${}^{\text{th}}$ month visit, lower WOMAC stiffness scores were obtained in the PRP group compared to PRP group ( $p=$ 0.024).

For WOMAC physical function scores, no significant difference was observed between PRP and PRP $+$ ozone groups in pre-treatment, 1 ${}^{\text{st}}$ and 6 ${}^{\text{th}}$ month visits ( $p>$ 0.05). WOMAC physical function scores at the 3 ${}^{\text{rd}}$ month visit was significantly lower in the PRP $+$ ozone group compared to the PRP group ( $p<$ 0.001).

There were no significant differences between 2 groups, in pre-treatment and post-treatment WOMAC total scores at the 1 ${}^{\text{st}}$ month visit ( $p>$ 0.05). WOMAC total scores at post-treatment month 3 was significantly lower in the PRP $+$ ozone group compared to the PRP group ( $p<$ 0.001). On the contrary, in the PRP group WOMAC total scores at month 6 were lower than the PRP $+$ ozone group ( $p=$ 0.024).

There were no significant differences between PRP group and PRP $+$ ozone group, in pre-treatment and post-treatment VAS scores at month 1 and month 6 ( $p>$ 0.05). The VAS score at post-treatment month 3 was significantly lower in the PRP $+$ ozone group compared to the PRP group ( $p<$ 0.001) suggesting an earlier efficacy (Fig. 3).

Figure 2.

Change in WOMAC total scores.

Figure 3.

Change in VAS scores.

Table 2

Pre- and post-treatment evaluations in PRP and PRP $+$ Ozone groups

	(Mean $\pm$ SD/ $n$ – %)	(Median)	(Mean $\pm$ SD/ $n$ – %)	(Median)	$p$
	PRP treatment		PRP $+$ Ozone treatment
WOMAC pain
Pre-treatment	15.7 $\pm$ 2.8	15.0	15.7 $\pm$ 2.9	15.0	0.987 ${}^{\text{a}}$
1 ${}^{\text{st}}$ Month	7.1 $\pm$ 1.9*	7.0	7.0 $\pm$ 2.1*	7.0	0.822 ${}^{\text{a}}$
3 ${}^{\text{rd}}$ Month	7.3 $\pm$ 1.7*	7.0	7.0 $\pm$ 0.0*	7.0	0.064 ${}^{\text{a}}$
6 ${}^{\text{th}}$ Month	7.0 $\pm$ 0.0*	7.0	7.0 $\pm$ 0.0*	7.0	1.000 ${}^{\text{a}}$
Intra-group variance ( $p$ )	$<$ 0.001 ${}^{\text{c}}$		$<$ 0.001 ${}^{\text{c}}$
WOMAC stiffness
Pre-treatment	6.1 $\pm$ 1.5	6.0	6.1 $\pm$ 1.5	6.0	0.925 ${}^{\text{a}}$
1 ${}^{\text{st}}$ Month	3.0 $\pm$ 0.8*	3.0	3.0 $\pm$ 0.9*	3.0	0.855 ${}^{\text{a}}$
3 ${}^{\text{rd}}$ Month	3.1 $\pm$ 0.8*	3.0	3.3 $\pm$ 0.4*	3.0	0.119 ${}^{\text{a}}$
6 ${}^{\text{th}}$ Month	3.3 $\pm$ 0.4*	3.0	3.5 $\pm$ 0.5*	4.0	0.024 ${}^{\text{a}}$
Intra-group variance ( $p$ )	$<$ 0.001 ${}^{\text{c}}$	$<$ 0.001 ${}^{\text{c}}$
WOMAC physical function
Pre-treatment	53.4 $\pm$ 10.8	51.0	53.9 $\pm$ 10.9	51.0	0.955 ${}^{\text{a}}$
1 ${}^{\text{st}}$ Month	20.4 $\pm$ 6.7*	19.0	19.6 $\pm$ 6.7*	19.0	0.552 ${}^{\text{a}}$
3 ${}^{\text{rd}}$ Month	22.6 $\pm$ 5.1*	20.0	19.0 $\pm$ 0.2*	19.0	$<$ 0.001 ${}^{\text{a}}$
6 ${}^{\text{th}}$ Month	19.0 $\pm$ 0.0*	19.0	19.0 $\pm$ 0.0*	19.0	1.000 ${}^{\text{a}}$
Intra-group variance ( $p$ )	$<$ 0.001 ${}^{\text{c}}$		$<$ 0.001 ${}^{\text{c}}$
WOMAC total
Pre-treatment	78.4 $\pm$ 15.2	75.0	78.9 $\pm$ 15.5	75.0	0.875 ${}^{\text{a}}$
1 ${}^{\text{st}}$ Month	31.9 $\pm$ 9.7*	30.2	30.9 $\pm$ 10.1*	30.2	0.587 ${}^{\text{a}}$
3 ${}^{\text{rd}}$ Month	34.4 $\pm$ 6.9*	33.3	30.5 $\pm$ 0.5*	30.2	$<$ 0.001 ${}^{\text{a}}$
6 ${}^{\text{th}}$ Month	30.5 $\pm$ 0.5*	30.2	30.7 $\pm$ 0.5*	31.3	0.024 ${}^{\text{a}}$
Intra-group variance ( $p$ )	$<$ 0.001 ${}^{\text{c}}$		$<$ 0.001 ${}^{\text{c}}$
Pain VAS
Pre-treatment	7.3 $\pm$ 1.1	7.0	7.2 $\pm$ 1.3	7.0	0.903 ${}^{\text{a}}$
1 ${}^{\text{st}}$ Month	3.6 $\pm$ 0.7*	4.0	3.7 $\pm$ 0.7*	4.0	0.838 ${}^{\text{a}}$
3 ${}^{\text{rd}}$ Month	3.2 $\pm$ 0.6*	3.0	1.0 $\pm$ 0.0*	1.0	$<$ 0.001 ${}^{\text{a}}$
6 ${}^{\text{th}}$ Month	2.6 $\pm$ 0.4*	3.0	2.6 $\pm$ 0.5*	3.0	0.509 ${}^{\text{a}}$
Intra-group variance ( $p$ )	$<$ 0.001 ${}^{\text{c}}$	$<$ 0.001 ${}^{\text{c}}$
Hyper-inflammation	14 31%		3 8.6%		0.014 ${}^{\text{b}}$
Day 10 pain VAS	10 22%		1 2.9%		0.013 ${}^{\text{b}}$

${}^{\text{a}}$ : Mann-Whitney U test, ${}^{\text{b}}$ :Chi-square test, ${}^{\text{c}}$ : Friedman test (Wilcoxon test), PRP: Platelet-rich-plasma, SD: Standard deviation, *: Significant difference when compared to pre-treatment ( $p<$ 0.05).

In the PRP $+$ ozone group, VAS scores on Day 10 and hyper-inflammation were significantly lower compared to the PRP group ( $p=$ 0.014 and $p=$ 0.013, respectively) (Table 2).

4. Discussion

In this study efficacy of PRP treatment alone was compared to PRP treatment in combination with ozone gas injection in patients with early stage knee OA. Even though similar efficacy was observed between two treatment regimens, patients receiving combined ozone treatment were less likely to experience post-injection pain and were more likely to recover faster when compared to patients receiving PRP treatment alone.

Currently there are very few studies comparing efficacy between PRP and PRP $+$ ozone treatments. In the literature, there’s only one similar retrospective study conducted by Sabanci et al. [15], which evaluated the efficacy of PRP treatment combined with ozone. In that study, patients were not clinically evaluated, and outcomes were evaluated in terms of VAS scores after administration of different doses of ozone, combined with PRP. In our study, evaluation of clinical outcomes, administration of WOMAC questionnaire in addition to VAS evaluation, and comparison or results with and without ozone treatment may be considered as additional values. According to our knowledge, this study was the only study comparing the intraarticular treatment with and without ozone treatment. In the current study, patients in the group receiving PRP + ozone demonstrated a better well-being in terms of pain and functions, compared to the other group. In addition to VAS scores, evaluation of WOMAC scores may make this current study considerably more reliable.

In recent years, ozone injections have become widespread like PRP treatment, especially in the treatment of knee OA [18, 19]. In most of the studies efficacy was detected using WOMAC questionnaire in OA patients. In observational and case series studies, ozone was determined to be an efficient treatment for various diseases [12, 20, 21]. Ozone therapy can basically induce moderate oxidative stress and inhibit inflammatory responses [10, 22]. In a randomized, placebo-controlled, double-blind study, ozone was identified as an efficient treatment method for pain relief (evaluated using VAS) and improvement in functional status (evaluated using WOMAC) in the treatment of knee OA. The study showed that post-treatment efficacy reached the maximum level in 8 ${}^{\text{th}}$ week [19]. In a study conducted by Mishra et al. [20], it was concluded that ozone therapy was more efficient at 6-month follow-up compared to steroid injections in the treatment of knee OA. In a study comparing intraarticular dextrose and ozone treatments, ozone therapy combined with dextrose, administered three times every 10 days, showed positive impact on pain and functional status in patients with early- and mid-stage OA [12]. In another study, patients with knee OA received hyaluronic acid, ozone and a combination of both methods. All three groups demonstrated a statistically positive and significant impact on pain, symptoms, daily living activities and quality of life [18]. In a study conducted by Giombini et al. [22], efficacy in patients receiving ozone combined with hyaluronic acid injection was higher compared to patients receiving hyaluronic acid or ozone alone. This present study also showed that the WOMAC total and WOMAC stiffness scores, especially at month 6, were better in patients receiving PRP $+$ ozone treatment, compared to the group receiving PRP alone. Results of this study promote that combination therapies can provide more positive effects compared to single therapies.

Feng and Beiping [18], evaluated the efficacy of ozone injection, using pain intensity (VAS), in patients with knee OA, receiving oral treatment as celecoxib and glucosamine hydrochloride administration. The pain score and functional status significantly improved in both groups. However, efficacy was demonstrated earlier in the combined therapy group (ozone $+$ oral treatment) comparing to oral treatment alone [18]. Similarly in this study the effect started earlier in the combined treatment group (PRP $+$ ozone group) and well-being was maintained until 6 ${}^{\text{th}}$ month. Especially, control at 10 ${}^{\text{th}}$ day after treatment revealed that the PRP $+$ ozone group had fewer complications such as less hyper-inflammation and pain compared to the PRP alone group.

In the present study, the evaluation of complications at 10 ${}^{\text{th}}$ day after treatment also showed that pain and hyper-inflammation levels were significantly lower than the PRP $+$ ozone group. This can be related to the faster onset of action of ozone [18]. Although PRP treatment has no known side effects, it is known that it can rarely cause hyper-inflammation at the administration site. The reason of this reduced hyper-inflammation rate may be due to the growth factors that are present in the thrombocytes [23]. Fewer hyper-inflammation detected in the PRP $+$ ozone group was a positive finding in terms of safety, mechanism of action and efficacy of ozone, and may be related to the inhibitory effect of ozone for inflammation [18].

Since PRP and ozone therapies have a positive impact especially on the progression of OA, they have been used frequently in the treatment of knee OA in recent years. In the light of this information, this study aimed to evaluate the efficacy of ozone therapy combined with PRP. The main limitation of this study was its retrospective nature. The cause of this limitation was unavailability of the ozone generator in the clinical unit. Lack of biochemical or histopathologic examinations, small sample size, as well as female dominancy due to absence of randomization may be considered as other limitations of our study. However, study results reached significance and suggested that PRP treatment combined with ozone has a faster onset of action and fewer complications. According to current knowledge, this study was the only study in the literature that compared efficacy of PRP treatment to PRP $+$ ozone treatment in patients with knee OA. Providing new approaches will be aimed for knee OA treatment in the future by utilizing different combinations of the injection methods used in the treatment of knee OA.

5. Conclusions

In general, similar efficacy was observed between treatment with PRP in combination with ozone and treatment with PRP alone. Patients receiving combined ozone treatment are less likely to experience post-injection pain and are more likely to recover faster when compared to patients receiving PRP treatment alone. Different combination studies can provide new approaches for knee OA treatment in the future.

Footnotes

Conflict of interest

The authors have no conflict of interest to declare.

References

Loeser

Goldring

Scanzello

Goldring

. Osteoarthritis: A disease of the joint as an organ. Arthritis Rheum 2012; 64(6): 1697-707.

Lim

Vos

Flaxman

Danaei

Shibuya

Adair-Rohani

, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: A systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012; 380(9859): 2224-60.

Marx

. Platelet-rich plasma (PRP): What is PRP and what is not PRP? Implant Dent 2001; 10(4): 225-8.

Tayapongsak

O’Brien

Monteiro

Arceo-Diaz

. Autologous fibrin adhesive in mandibular reconstruction with particulate cancellous bone and marrow. J Oral Maxillofac Surg 1994; 52(2): 161-5, (discussion 6).

Raeissadat

Rayegani

Hassanabadi

Fathi

Ghorbani

Babaee

, et al. Knee osteoarthritis injection choices: Platelet-rich plasma (prp) versus hyaluronic acid (a one-year randomized clinical trial). Clin Med Insights Arthritis Musculoskelet Disord 2015; 8: 1-8.

Rayegani

Raeissadat

Taheri

Babaee

Bahrami

Eliaspour

, et al. Does intra articular platelet rich plasma injection improve function, pain and quality of life in patients with osteoarthritis of the knee? A randomized clinical trial. Orthop Rev (Pavia) 2014; 6(3): 5405.

Sundman

Cole

Karas

Della Valle

Tetreault

Mohammed

, et al. The anti-inflammatory and matrix restorative mechanisms of platelet-rich plasma in osteoarthritis. Am J Sports Med 2014; 42(1): 35-41.

Harris

Bonewald

Harris

Sabatini

Dallas

Feng

, et al. Effects of transforming growth factor beta on bone nodule formation and expression of bone morphogenetic protein 2, osteocalcin, osteopontin, alkaline phosphatase, and type I collagen mRNA in long-term cultures of fetal rat calvarial osteoblasts. J Bone Miner Res 1994; 9(6): 855-63.

Cardile

Jiang

Russo

Casella

Renis

Bindoni

. Effects of ozone on some biological activities of cells in vitro . Cell Biol Toxicol 1995; 11(1): 11-21.

10.

Manoto

Maepa

Motaung

. Medical ozone therapy as a potential treatment modality for regeneration of damaged articular cartilage in osteoarthritis 2016.

11.

Al-Jaziri

Mahmoodi

. Painkilling effect of ozone-oxygen injection on spine and joint osteoarthritis. Saudi Med J 2008; 29(4): 553-7.

12.

Hashemi

Jalili

Mennati

Koosha

Rohanifar

Madadi

, et al. The effects of prolotherapy with hypertonic dextrose versus prolozone (intraarticular ozone) in patients with knee osteoarthritis. Anesth Pain Med 2015; 5(5): e27585.

13.

Zhou

Cheng

. Treatment of middle-aged and aged patients with knee osteoarthritis of yang-deficiency induced cold-damp syndrome by ozone combined Chinese materia medica: A clinical research. Zhongguo Zhong Xi Yi Jie He Za Zhi 2013; 33(4): 471-5.

14.

Wang

Dong

Yan

. Case-control study on therapeutic effects of ozone and triamcinolone acetonide on the treatment of meniscal injury. Zhongguo Gu Shang 2014; 27(4): 295-8.

15.

Sabanci

Yildiz

Akcali

Karamercan

Diracoglu

, et al. Comparison of the effects of intraarticular ozone and intraarticular PRP in patients with osteoarthritis. Turk J Integr Med 2015; 3(2): 31-4.

16.

Chang

Hung

Aliwarga

Wang

Han

Chen

. Comparative effectiveness of platelet-rich plasma injections for treating knee joint cartilage degenerative pathology: A systematic review and meta-analysis. Arch Phys Med Rehabil 2014; 95(3): 562-75.

17.

Bellamy

Buchanan

Goldsmith

Campbell

Stitt

. Validation study of WOMAC: A health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988; 15(12): 1833-40.

18.

Feng

Beiping

. Therapeutic efficacy of ozone injection into the knee for the osteoarthritis patient along with oral celecoxib and glucosamine. J Clin Diagn Res 2017; 11(9): UC01-UC3.

19.

Lopes de Jesus

Dos Santos

de Jesus

Monteiro

Sant’Ana

Trevisani

VFM

. Comparison between intra-articular ozone and placebo in the treatment of knee osteoarthritis: A randomized, double-blinded, placebo-controlled study. PLoS One 2017; 12(7): e0179185.

20.

Mishra

Pramanik

Das

Palit

, et al. Role of intra-articular ozone in osteoarthritis of knee for functional and symptomatic improvement. Ind J Phys Med Rehabilit 2011; 22(2): 65-9.

21.

Benvenuti

. Oxygen-ozone treatment of the knee, shoulder and hip: A personal experience. Rivista Italiana di Ossigeno-Ozonoterapia 2006; 5: 135-44.

22.

Giombini

Menotti

Di Cesare

Giovannangeli

Rizzo

Moffa

, et al. Comparison between intrarticular injection of hyaluronic acid, oxygen ozone, and the combination of both in the treatment of knee osteoarthrosis. J Biol Regul Homeost Agents 2016; 30(2): 621-5.

23.

Kaux

Croisier

Leonard

Le Goff

Crielaard

. Exuberant inflammatory reaction as a side effect of platelet-rich plasma injection in treating one case of tendinopathy. Clin J Sport Med 2014; 24(2): 150-2.