Cross-linked hyaluronic acid in the treatment of osteoarthritis of the knee--results of a prospective randomized trial

PURPOSE: The objective of this trial was to compare the effectiveness of intraarticular injection of highly cross-linked hyaluronic acid (HA) with intraarticular injection of gaseous oxygen (O 2 ) in patients with clinical symptoms of cartilage damage in the knee. METHODS: Based on arthroscopically verified diagnosis, 111 patients were randomised and treated prospectively either with HA or O 2. The treatment was completed with an exercise program. The follow up was one year. 109 patients (56 x HA, 53 x O 2 ) were statistically calculated with the Wilcoxon-test according to the results of the Lysholm-score, the Tegner-activity-index, the Womac-score for pain, stiffness, function and the VAS for pain in rest and under strain. RESULTS: Both treatments were able to attain a statistically significant reduction of pain (VAS in rest and under strain, Womac part A), a reduction of joint stiffness (Womac part B) and improvement of joint function (Womac part C, Lysholm-score) during the follow up of one year. The Tegner-activity-index showed no significant change under both treatments. The comparison of both treatments showed differences in VAS under strain (p = 0.001), the Lysholm-score (p = 0.003), Womac part A (p = 0.003) and part C (p = 0.001). As a result HA showed significant better improvements with the VAS and Lysholm-score and oxygen showed significant better changes in the Womac-score part A and C. The results with cartilage damage 2 degrees were the same as in the total (VAS strain: p = 0.029 for O 2, Lysholm-score: p = 0.003 for HA, WOMAC part A: p = 0.009 for HA, Womac part C: p = 0.006 for O 2 ). The results with cartilage damage 3 degrees showed significant differences in reduction of joint stiffness (Womac part B: p = 0.012) for O 2. For cartilage damage 4 degrees HA showed significant reduction of pain (VAS rest: p = 0.001, VAS strain: p = 0.003) and O 2 significant reduction of pain and function (Womac part A: p = 0.004, part C: p = 0.002). CONCLUSION: Both methods are suitable to improve significantly the discomfort due one year to osteoarthritis. The pain relief by HA and the improvement of joint function by O 2 treatment have been shown for higher degrees of cartilage damage.