Bisphosphonate Therapy Preserves Knee Joints

SAN DIEGO?In addition to protecting against osteoporotic bone loss, the bisphosphonate risedronate (Actonel) ?ap??pears to delay joint destruction and the need for joint replacement in patients with knee osteoarthritis (OA). Data ?presented at the annual meeting of the American College of Rheuma?tology show?ed that the drug helps preserve the subchondral bone that supports the ?cartilage of the articular surfaces of the knee.

J. Christopher Buckland-Wright, PhD, of King's College London, compared a joint to the roof of a house, with the tiles representing the cartilage and the rafters representing subchondral bone. The structural integrity of the rafters has to be maintained to prevent the roof from falling in, he said, pointing to photomicrographs of subchondral bone that showed a loss of the vertical trabecular bars that support the bony plate under the cartilage. "In time, the joint begins to collapse," he said.

Groups of about 300 patients with knee OA and 2 to 4 mm of joint space narrowing at baseline received risedronate, either 5 or 15 mg/day or 50 mg once weekly, or placebo for 2 years. A novel computational technique was applied to standard radiographs to gauge the bone structure in the medial tibial compartment of the knee. Patients were stratified according to whether they had little or no (static) joint space narrowing (<0.6 mm) or advanced (progressive) narrowing (>=0.6 mm).

In "patients with progressive joint disease?the 15-mg/day dose halted the bone loss, whereas the 50 mg [dose] given once a week reversed the process," Dr Buckland-Wright reported. "It put bone back into the joint, thereby restoring some of the lost bone." The lower doses were not beneficial. Of interest, the static group experienced a modest loss of bone structure regardless of dose over the 2-year period.

Dr Buckland-Wright concluded that despite cartilage loss, higher doses appear to protect knees against bone loss and preserve their structural integrity. He predicted that bisphosphonate therapy will prevent or delay compartmental collapse from subchondral bone loss and delay the need for knee arthroplasty, depending on the degree of local bone loss and the general quality of the bone in an individual patient.

Since none of the bisphosphonates is approved for preventing OA joint damage, "it's up to clinicians to make that decision," he said, noting the generally good safety record of long-term bisphos??phonate use. ?D.M.K.