Objective: Strontium ranelate significantly decreases the risk of osteoporotic fractures. The objective of the present study was to investigate whether strontium ranelate (2 g/day) also affects cartilage brakedown as measured by urinary marker of cartilage degradation, designated CTX-II.

Methods: A subgroup of 2617 postmenopausal osteoporotic women (aged 75.7+/-4.4 years) were selected from the TROPOS phase III study on the basis of a urinary sampling reported at each visit during the first three years of the study. When included in TROPOS, they were randomized to strontium ranelate or placebo in a double-blind fashion for 3 years. A calcium and vitamin D supplement was also provided to the subjects during the study. A marker of collagen type II degradation (CTX-II) corrected for urinary creatinine (CTX-II/cr.) was assessed at regular intervals throughout the study in 1310 patients in strontium ranelate group and 1307 patients in placebo group.

Results: The response in CTX-II depended on time (p<0.0001), and this time dependency differed statistically significantly between groups (time x treatment) (p<0.0003). In addition, there was a statistically significant difference between treatments (p<0.0001). The difference in the response of CTX-II/cr. appeared already after three months, with the strontium ranelate-treated subjects having approximately 15-20% lower values than the placebo-treated subjects for the remaining study period (p<0.0001).

Conclusion: Treatment with strontium ranelate significantly decreases urinary excretion of CTX-II, a marker of cartilage destruction. Further studies are warranted to investigate an effect on cartilage formation and symptoms of osteoarthritis.