Walter was 16 years old and a rising soccer star. His community men's team had recruited him to play with them. That team, he reports, was "loaded with former pros and standout college players." It played against many of the colleges that were scouting Walter. He was grateful for the exposure: "That team was the 'route to riches.'" His coaches thought that a career as a professional soccer player was a realistic goal.

Then one day he landed at an awkward angle during practice. His right leg extended unnaturally far, and practice swiftly halted as other players nearby reacted to the loud popping sound they heard. "The pain was immediate and severe, and my knee began to swell almost immediately," Walter recalls.

In the emergency room, they told him that he had suffered a sprain. He was issued crutches and told to stay off the knee for a few weeks. They assured him that he'd be fine to attend a very competitive national training camp a few weeks later -- the first big step toward a pro career.

He ended up participating in the camp's training for all of 10 minutes.

After a routine jump, Walter reports, "My knee collapsed, severely hyper-extending and hyper-rotating nearly 90 degrees clockwise. I remember this well, because the angle of my fall gave me a perfect view. As you might imagine, such a sight also burns into your memory quite vividly."

One of the coaches sprinted over, shouting, "Don't move!" as he ran. Walter remembers that the coach had to calm him down before he could look at his knee. He recalls wryly, "It took me several seconds to realize that the annoying screams that kept me from hearing the coach clearly were mine."

The coach was also a certified athletic trainer. After quickly examining Walter, he said, "I heard your knee go from almost 50 yards away. . . You are going to be having a very serious conversation with an orthopedic surgeon." One of the tests that he did on the field takes longer to name than to perform: the Lachman test for integrity of the ACL, the anterior cruciate ligament. It showed that Walter's ACL had big problems.

After surgery, Walter found out that the simple Lachman test had been right on target. He recalls, "The ACL had already been nearly completely ruptured from the first injury. Then it had withered in the weeks since then due to lack of blood supply. The ACL is one of only four ligaments that connect two major bones. For this reason, the loss of the ACL is akin to driving a car on three wheels. The joint isn't stable." He had also broken his tibia -- a large bone between the knee and the ankle -- as a result of the fall he took when he played with a ruptured ACL.

The emergency room doctors a few weeks earlier had not performed the Lachman test. It doesn't require any special equipment. It involves placing one hand above the knee and one below, in specific positions, and applying a little pressure. If they had done the test, they would not have told Walter that he had a sprain. He would have arranged to see a specialist. He would not have set himself up for the second devastating injury by playing with a severely damaged ligament.

As it was, he ended up needing two operations within two years, and bouts of rehabilitation that felt almost like a full-time job: "Each of the surgeries required two years of rehab. That's four years of rehab in five... I lost my senior season of high school, and three of my five years of college eligibility to rehab. In each case, there was no guarantee that I'd be able to play again. So the mental and emotional pressures were easily as heavy as the physical. And the physical was daunting, to say the least."

Of course, any serious athlete faces the risk of career-ending injury. However, in Walter's case, the fact that the doctors didn't correctly identify his first injury set the stage for the next one. That mistake almost guaranteed that the second one would be much, much worse.

Through single-minded focus and determination, Walter did end up with a college scholarship to play soccer. He even had a brief pro career. However, his experience would have been vastly different if he had not been misdiagnosed in the emergency room the first time. He has since had two additional operations. He faces a fifth in the near future. He has also had to stop playing entirely, decades before he expected to.

"In addition, the imbalances to the body caused by protecting the right knee over the years created problems elsewhere. I've since required surgery on both the left knee and ankle. Since age 16, I've never walked without being conscious of my environment and foot placement."

You may not be a nationally ranked athlete. Still, Walter's experience highlights key points that can help you avoid major problems if you are treated in the emergency room.

It may help to think of emergency rooms as waystations intended to prevent people from dying in emergencies that compromise ABCs. These are Airway, Breathing, and Circulation (blood flow). If you end up being admitted to the hospital, it is clear that the ER is not the final step in your care. What many people don't realize is that the same is true if you are sent home. Think of emergency room care as a temporary fix. It can stabilize you until you can see your doctor or the appropriate specialists in their offices during normal business hours.

As Walter noted, "Being respectful of your professional's skill and training doesn't mean that you give up your right to ask questions. Never forget that doctors are not gods. Emergency room doctors in particular are generalists, not specialists. Be bold. Ask questions. Remember that your doctor works for you and is not infallible."

Misdiagnosis in the emergency room can run as high as 40 percent. Knowing this fact can help you avoid putting your full weight, so to speak, on the diagnosis you are given. Boiled down to the basics, emergency room doctors are trying to answer one simple question: Are you at risk of dying right now? Once they conclude that the answer is "No," they may sometimes mentally move on to the next patient -- because for that patient, the answer may be "Yes." The distinction between a sprain and a ligament tear might not seem like a crucial one to make to harried doctors in the emergency room.