This was a pilot, single blind, randomised, controlled study in patients requiring partial meniscectomy. The aim was to assess whether replacing the synovial fluid lost during arthroscopy with a hyaluronic acid-containing synovial fluid substitute (Viscoseal) would reduce the severity and duration of post-operative symptoms during the 4 weeks post-surgery, in comparison to the standard arthroscopy procedure alone. Fifty patients were randomly assigned to either undergo arthroscopic partial meniscectomy alone (control group: n=25) or to receive 10 ml Viscoseal into the joint at the end of the procedure (Viscoseal group: n=25). Forty patients (20 per group) completed the study. Despite the small patient population in this pilot study, some interesting results were obtained. On Day 1 after surgery, the mean values for pain at rest (VAS) increased in both groups but this increase was lower in the Viscoseal group (8.9+/-23.1 mm) than in the standard therapy group (20.0+/-25.9 mm) (Mann-Whitney statistic MW-S: P=0.0525) and remained in favour of Viscoseal for the first 3 days after surgery. Joint swelling decreased to a greater extent in the Viscoseal group with an observed superiority at Day 7 (MW-S: P=0.1187) and a proven superiority at Days 12 (MW-S: P=0.015) and 28 (MW-S: P=0.0072). Diclofenac intake was lower in the Viscoseal group from Day 3 to Day 28 with a proven superiority (LB-CI > 0.5) in favour of Viscoseal on Days 3 (MW-S: P = 0.0093), 4 (MW-S: P= 0.0075), and 7 (MW-S: P = 0.0195) indicating that the product had an NSAID-sparing effect. Viscoseal was safe and well-tolerated and no adverse reactions occurred during the study. These findings indicate that Viscoseal may be useful as a synovial fluid substitute after arthroscopy.