If you’re thinking about having knee replacement surgery, you’re in good company. Every year, more than a half-million Americans opt for the procedure. Many people have knee replacements (also called knee arthroplasty) because they have osteoarthritis. This condition occurs when the cartilage (tissue) that cushions the knee joint wears away. As a result, bone rubs against bone, which is quite painful. Other people may need a new knee because they have rheumatoid arthritis, a disease that causes chronic joint inflammation. Still others may have had an injury causing knee pain and limiting function. These conditions are known to cause gradual worsening of knee pain over a long period of time. It’s not always easy to know when knee replacement surgery is necessary. You and your doctor will take several factors into account in deciding if (or when) joint replacement is right for you. These factors include your X-ray or MRI results, pain level, physical function, personal health history, and weight. Here are high-level guidelines that can help you prepare for a conversation with your doctor about moving forward with knee replacement. Why You Might Say "Now’s the Time" Here are seven signs that the time might be right for a knee replacement: Medications—even stronger anti-inflammatory drugs—don't help, or no longer help ease your pain. Other less invasive treatment options don’t effectively reduce your pain and inflammation. These may include cortisone injections, lubricating injections, rest, and physical therapy. You have lots of difficulty and pain performing everyday tasks, such dressing, bathing, getting out of bed or a chair, or climbing stairs. You need the aid of a cane or walker to get around. Your pain is severe day and night. The pain is there even when you’re not using your knee, such as when you’re sitting still or lying down. Your knee has become deformed from injury or arthritis. It bows in or out. (However, in some cases, severe deformity can make surgery more difficult. If you start to feel severe deformity, talk with your doctor sooner than later.) You are between 50 and 80 years old. Most people who get knees replaced are in this age range. (However, age is not necessarily a deciding factor. Surgeons successfully perform knee replacements on patients of all ages.) Why You Might Say "Not Yet" Here are a five reasons knee replacement might not be right for you—at least for now: You still have time to give more conservative treatments a chance to work. These options include rest, ice, heat, muscle-strengthening exercises, and pain medications. Your pain is bearable, and medications are helping. You can still get around and do your normal activities without much difficulty. You have weak thigh muscles that wouldn’t be able to support a new knee joint. Or, you have open sores or ulcers in the area that could easily become infected after surgery. You are very overweight. Extra weight puts more pressure on your knees, and may move parts of the artificial knee joint. This can lead to pain or further surgery. Have a Conversation With Your Doctor Before you make up your mind about having your knee replaced, talk with your doctor about the possible risks of surgery. These can include infection, loosening of the knee replacement parts, and movement limitations. Also, talk about any health conditions you might have that could make the operation and your recovery more difficult. It’s also important to have realistic expectations for how quickly you will recover from the surgery. It can take several weeks to several months to feel back to normal after a knee replacement. You’ll also need to commit to physical therapy and exercise. Your doctor can talk through the factors that can speed up or slow down recovery, and help you decide if the timing is right. Under the right circumstances, a knee replacement can significantly boost your quality of life. More than 90% of people who get new knees are able to resume their normal activities shortly afterward and are happy with the results, according to the American Academy of Orthopaedic Surgeons. And pinpointing a good time to have a knee replacement is a key part of having success with the procedure.