Background: Commonly used oral once weekly (ow) bisphosphonate therapy for bone diseases is accompanied by various adverse effects. However, information regarding the musculoskeletal adverse effects (MAEs) is scarce.

Objectives: To evaluate whether alendronate (ALN) or risedronate (RSN) given orally ow could produce MAEs and which among ALN / RSN had a greater propensity to cause MAEs?

Methods: One hundred and twelve osteoarthritic patients on ow oral ALN 35 mg or RSN 35 mg from orthopaedic clinics were examined and followed up for MAEs, using Short Form McGill Pain Questionnaire (SFMPQ).

Results: Eighteen (16.07%) patients reported MAEs after ALN / RSN treatment. Of the patients experiencing MAEs, 72.72% experienced MAEs after first dose in the RSN group while 71.42% experienced after the second dose in ALN group (p=0.927).

Conclusions: Oral ow ALN / RSN induced MAEs in 16.07% patients, any time between the first to fourth doses equally in both genders which rarely recurred after repeating the dose in the same patient.

Key words: Alendronate; adverse effects; osteoarthritis; risedronate.