In a recent blog entry, I talked about some of the more common knee problems that golfers experience. At that time, Tiger Woods had miraculously won the U.S. Open with a very painful knee (and some stress fractures in his leg to boot) that has been a recurrent issue with him.

Since then, Tiger has since shed some light on the real problem that has been bothering has knee for some time. He clearly did not have the typical "golfer's knee" - I guess that's what happens when you are not the typical golfer!

Apparently, about a year ago, Tiger somehow tore his anterior cruciate ligament (ACL). ACL tears are serious and most commonly happen in sports that require sudden acceleration and deceleration, especially when combined with cutting, side to side rapid maneuvers, such as that seen in basketball or soccer.

ACL tears are extremely uncommon in golf, unless someone has a freak accident or steps into a large unexpected hole, suddenly jarring their knee. According to Tiger's brief statements, he tore his knee while jogging (again, very rare unless there's a fall or sudden twist). When you tear your ACL, one of the most important stabilizing ligaments of the knee, your knee can feel unstable at times, occasionally buckling or going out on you.

Many individuals, especially if they are not athletes, can live and function quite well without an ACL. Golfers, even at the pro level, can often tolerate this type of instability, since golf does not require running, cutting and rapid change in direction. Pro basketball players cannot play or function well with a torn ACL. In fact, Tiger did pretty well over the past year with his torn ACL (who knows, maybe it was a partial tear, although partial tears are pretty rare).

When athletes (or anyone for that matter) have a torn ACL, the unstable "trick knee" can get into other troubles. You are more prone to cartilage tears (Tiger had a few of those) and also joint surface injuries that can lead to arthritis. Sometimes you get floating chips that have to be removed. This all makes Tiger's need for several knee scopes more understandable.

I suspect that the torn ACL was the predisposing problem prompting Tiger's prior arthroscopic surgery procedures. He just underwent ACL reconstruction surgery, replacing his torn ligament with a brand new one. This is a bigger procedure than the simple scopes he had in the past, with a longer recovery.

One other puzzle in the Tiger knee saga is how he developed "stress fractures" near the knee, leading up to the US Open. He had just had a knee scope 2 months prior and was doing rehab. Stress fractures in bones usually occur when someone is pounding and pushing their body pretty hard, more in a fitness manner, not typically in a rehabilitation setting.

Hopefully Tiger is comfortable and on the mend. He will have a tremendous amount of work ahead of him to try to get his knee back as close to 100% as possible. In recent years, with more modern minimal incision surgical techniques, we have done a tremendous job in getting athletes back with ACL injured knees.

We have also become more knowledgeable in terms of how to prevent ACL tears in the first place. Many of these preventive programs are also used after ACL reconstruction to make the newly reconstructed knee less vulnerable to re-tear.

One other caveat, if indeed he has sustained some damage to the knee joint surface over the past few years, then that may have longer-term consequences for him (i.e. higher likelihood of developing arthritis), but I suspect he will do well at least in the short term, and near future. It will take more than a bum knee to stop the mighty Tiger.