The lack of correlation between both OP and OA type II fiber atrophy and patients’ age could be explained by the fact that the primary causes of muscle atrophy in these two diseases (hormonal decline and Akt decrease for OP, and disuse due to pain and joint disability for OA) prevail over the effects of physiological muscle aging, as previously described in OA [25]. The gene discussed is AKT1; the disease is muscle atrophy.