On 2013 Oct 29, Hilda Bastian commented:

The results of this systematic review are contradicted by a more recent and more comprehensive analysis of the methodologically more rigorous trials of viscosupplementation of the knee (Rutjes AW, 2012). In that more recent review, Rutjes and colleagues identify significant publication bias as a contributing factor in previous over-estimations of the benefit of intra-articular injections.

Rutjes and colleagues conclude that the intervention has only a clinically irrelevant benefit on pain, no statistically significant effect on function and is associated with serious unexplained adverse events. They discourage the use of the intervention and suggest an individual patient data meta-analysis would be needed to explore the issue of adverse events.

Doubts about the potential for viscosupplementation of the knee to do more good than harm were also expressed in another systematic review published after that by Bellamy and colleagues (Samson DJ, 2007).

UPDATE: A network meta-analysis by Bannuru RR, 2015 was able to analyze intra-inarticular injections, intra-articular placebos, and oral placebos, as well as a range of active treatments. It found a clinically meaningful benefit from intra-articular hyaluronic acid injections, in large part attributable to the effects of intra-articular injections per se.

(I discussed the implications of the 2015 review in a February 2015 blog post.)

On 2013 Oct 29, Hilda Bastian commented:

The results of this systematic review are contradicted by a more recent and more comprehensive analysis of the methodologically more rigorous trials of viscosupplementation of the knee (Rutjes AW, 2012). In that more recent review, Rutjes and colleagues identify significant publication bias as a contributing factor in previous over-estimations of the benefit of intra-articular injections.

Rutjes and colleagues conclude that the intervention has only a clinically irrelevant benefit on pain, no statistically significant effect on function and is associated with serious unexplained adverse events. They discourage the use of the intervention and suggest an individual patient data meta-analysis would be needed to explore the issue of adverse events.

Doubts about the potential for viscosupplementation of the knee to do more good than harm were also expressed in another systematic review published after that by Bellamy and colleagues (Samson DJ, 2007).

UPDATE: A network meta-analysis by Bannuru RR, 2015 was able to analyze intra-inarticular injections, intra-articular placebos, and oral placebos, as well as a range of active treatments. It found a clinically meaningful benefit from intra-articular hyaluronic acid injections, in large part attributable to the effects of intra-articular injections per se.

(I discussed the implications of the 2015 review in a February 2015 blog post.)