Maurice,
In one of his lecture which I attended, the Nobelist Eric R. Kandel said that pain was associated with memory, to teach us a lesson and not to forget that experience. The results of a trial in advanced osteoarthritis patients with a new analgesic monoclonal antibody Tanezumab from Pfizer which blocks nerve growth factor in advanced osteoarthritis patients, show that without pain, patients damaged their knees by putting more stress. Thus having some pain may be a protective factor?
NEJM Paper : Lane, NE. Schnitzer, TJ. Birbara, CA., Mokhtarani, M. Shelton, DL. Smith, MD. Brown, MT. Tanezumab for the Treatment of Pain from Osteoarthritis of the Knee.
September 29, 2010 (10.1056/NEJMoa0901510)
Wood, JN. Nerve Growth Factor and Pain.September 29, 2010 (10.1056/NEJMe1004416)
Treatment with tanezumab was associated with significant reduction of joint pain and improvements in functions. The most common drug related ADRs were headache, upper respiratory infections and paresthesia. Tanezumab seems to be free from traditional analgesic side effects like ulcers, GI toxicity, hepatotoxicity, increased cardiovascular risk and provides sustained pain relief for upto 2 months with a single injection. Significant pain reduction may have contributed to the overuse of joints in some patients leading to accelerated knee replacement. Thus Chronic pain may have a protective role in joint protection? As most of the advanced OA patients are likely to progress to joint replacement surgery, the paradox of a drug providing pain relief and accelerated OA and knee replacement surgery requires open debate to define a way forward in the best interests of patients.
It is in the best interest of patients to live pain free and have the inevitable knee/hip replacement surgery done earlier. It seems that tanezumab is not causing the accelerated joint destruction but the pain free patients putting more stress on joints.
http://knol.google.com/k/krishan-maggon/tanezumab-pfizer-review-chronic-pain/3fy5eowy8suq3/121#