Traditional and labeled use of Hyaluronic Acid (HA) Orthovisc® for treatment of pain due to OA of the knee involves a series of 2 ml (30 mg of HA: 15 mg/ml) injections weekly in the clinic over a span of three weeks. Some studies have documented the complication rate of this injection to be as high as 27% , with the most complication being injection site pain. Other complications of significance are transient local reactions in the injected joint, which are typically benign, short lived, without sequelae, and similar to those observed with any intra-articular treatment . These adverse reactions have been found to occur at a rate of 2–4% .
In this study using 6 ml/90 mg of Orthovisc®, no complications were noted at the 6 months follow up time period. The presence of minimal joint swelling was observed in several patients at the earlier follow up appointments which can be attributed to the arthroscopic procedure; however, none of these patients were symptomatic and all resolved by the 6 months appointment. No patients had evidence of infection, transient reactions, deep venous thrombosis, or other neurovascular insult. Delivery site pain and reaction may have occurred but could remain disguised by post surgical pain or narcotic use (Vicodin). Because of these influences, the ability of our study to detect delivery site pain or other related symptoms were somewhat limited. Overall, we found that 6 ml/90 mg of Orthovisc® can be given safely at the time of arthroscopy without any adverse complications. However, this statement can not be generalized to all HA supplements as Orthovisc® was the only HA used in our study. Ulucay et al. showed no difference in the complications between three different HA formulations (Orthovisc, Adant, and Synvisc) after arthroscopic knee debridement for OA .
The dosing effect of giving 6 ml/90 mg of Orthovisc® when compared to three separate injections raises concern. Several meta-analysis on investigating the safety and efficacy of HA injections show that the standard dosing is safe and effective [25, 31, 32]. Our pilot study results showed at least equivalent efficacy and safety at the six-month mark. We did not observe any adverse events at the 6 months time period with the increased dosage of 6 ml/90 mg of Orthovisc®. Bellamy et al.  in a meta-analysis found that WOMAC pain scores peaked between 5 and 13 weeks and tended to deteriorate towards baseline over 52 weeks. Brandt et al.  in a randomized control trial of 226 patients found that HA injections improved WOMAC pain scores for the duration of the study of 30 weeks. Neustadt et al.  in a randomized control trial of 272 patients followed over a period of 28 weeks showed that a WOMAC pain scores improved by greater than 40% in patients receiving HA when compared to those receiving placebo. Our study showed consistently improved WOMAC pain scores after 24 weeks with a single delivery of 6 ml/90 mg of Orthovisc® at the time of the arthroscopic debridement with over 79% of our patients having an improvement of greater than 40%. However the final follow up in our study was at the six month mark, so we can not conclude that the improvement in WOMAC pain score would be sustained for greater than one year.
Dervin et al.  performed a study examining the outcomes of arthroscopic debridement alone on arthritic knees. They found 44% of the patients in the study sustained a significant decrease in WOMAC pain scores over two years, where improvement was considered greater than 15%. Their study population composed of 126 patients with knee OA that is refractory to conservative management and with significant medial compartment disease (57% had ICRS Grade III or IV lesions) and meniscal tear (63%) which is similar to the patient population of our study. Compared to this historical control, our study showed that WOMAC pain scores from the combined procedure was significantly improved in 87% of our patients and SF-36 PCS scores improved in 89% of patients at the 6 months follow up. Furthermore, the patients in the bottom 25th percentile of the SF-36 PCS in our study improved from 29.9 (pre-op) to 45.8 at the 6 months follow up. However, the length of follow up (6 months) may have skewed our results.
In another study by Mathies et al.  HA injection was performed after arthroscopy for meniscal tears. He found that patients had less pain at rest and during exercise when compared to a control group. Patients in the HA group were also noted to have less joint swelling and better Lysholm scores. Hempfling el al.  in a recent study compared arthroscopic knee debridement and lavage for knee OA versus the same procedure with immediate injection of 10 ml of HA post arthroscopy. A total of 80 patients were followed prospectively for two years with 40 patients in each group. At the one year follow up time frame, patients in the debridement/lavage and HA group were found to have statistically longer lasting improvement in walking pain, night pain, and ability to walk 100 meters with no complications observed. It was concluded that the post-arthroscopic instillation of a HA-based synovial fluid substitute into the joint is a suitable way of achieving long-term stabilization of the treatment outcome. However, their study did not utilize WOMAC and SF-36 questionnaires to evaluate functional efficacy.
Although differences in the patient population and indication for arthroscopy exist when compared to our study, these above published results correlate with our hypothesis that HA delivered at the time of arthroscopy for osteoarthritis of the knee can be performed safely with the preliminary data showing that the combined procedure is efficacious in improving patient's pain level and functional outcome.
Another key factor in determining success of the arthroscopy procedure for knee OA is patient selection. In a recent review of evidence based factors influencing arthroscopy for knee OA by Darling et al , the authors recommended arthroscopy for OA only in patients with short duration of symptoms, medial sided knee pain with localized tenderness, preservation of the joint space on radiograph, and mechanical symptoms. Patients with mechanical mal-alignment, flexion contracture, and obesity are not likely to have long term improvement after arthroscopy for knee OA. The above statements were also supported by several other studies [2, 11, 41]. The results from our study and other literature reports support the notion that the addition of HA injection at the time of the arthroscopy procedure for knee OA will result in better pain relief with sustained benefits in the right patient population.
There are several limitations in our study. One being that it is a case series, level IV evidence study with small sample size of twenty-three patients at the final follow up (6 months). Another significant limitation is that there were no control group and our data was compared to the historical controls found in literature with a short follow-up time of six months. This presents bias in terms of patient population heterogeneity and patient selection across the different studies. Also majority of our patients had menisectomy in addition to the chondroplasty which could result in the improved outcome scores. However, the strength of this study is that all the procedures were performed by a single surgeon (BB) and the results were collected prospectively. To our knowledge, this is also the first case series study evaluating the preliminary efficacy and safety of combined HA (Orthovisc®) injection at the time of arthroscopic debridement for OA of the knee utilizing the WOMAC and SF-36 questionnaires. Complications were also documented for this study group and it was shown that injection of 6 ml/90 mg of Orthovisc® was safe at the 6 months follow up.