Introduction The impact of knee joint loading exercise on MRI-assessed articular cartilage in osteoarthritis (OA) has only been reported by individual studies. We investigated the impact of knee joint loading exercise on MRI-assessed articular cartilage in people at risk of, or with established, knee OA, by conducting a systematic review of randomised controlled trials.

Methods We performed a literature search with no restriction on publication year or language on five major databases up to September 2017. A narrative synthesis of the effect of knee joint loading exercise on MRI-assessed articular cartilage thickness, volume, defects, glycosaminoglycans (GAG) and collagen was performed.

Results We included nine trials, involving 14 comparisons of different cartilage outcomes; two included participants at increased risk of knee OA and 12 included participants with knee OA. In participants at increased risk, one comparison reported no effect on cartilage defects and one had positive effects on GAG. In participants with OA, six comparisons reported no effect of knee joint loading exercise on cartilage thickness, volume or defects; one reported a negative effect and one no effect on GAG; two reported a positive effect and two no effect on collagen.

Conclusions Knee joint loading exercise seems to not be harmful for articular cartilage in people at increased risk of, or with, knee OA. However, the quality of evidence was low including some interventions considered to have too low or too high a dose to positively impact on cartilage, particularly for studies evaluating cartilage volume, thickness and defects.