When is the right time to have your knee replaced? Knee arthritis takes years to reach a true bone-on-bone end point. Each individual patient makes the decision to have a total knee replacement based on a number of factors. Generally, the younger you are, the longer you should wait to replace a joint. This is mostly because we know that knee replacements will not last forever. Recent papers suggest the average total knee replacement done with modern techniques and implants has a 90 percent chance of lasting 20 years. Of course this does not guaranty any particular knee will last this long. Revision knees may not last as long because the bone quality is not as good the second or third time around. All patients should exhaust all non-operative options before having a total knee. This includes physical therapy, steroid injections, anti-inflammatory medication, and sometimes arthroscopic debridement. When the knee pain makes it impossible to do the activities you want to do, such as tennis, golf, or hiking, then it is reasonable to proceed. If narcotics are needed to control the pain, that is also a sign that total knee replacement may be the best option. Your surgeon will take an Xray of the knee and if the joint is worn out, and the bones are touching, then you are likely close to your replacement. See an orthopedist who specializes in joint replacement, and who operates in a Total Joint Center if possible.