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Bob's ACL WWWBoard
Re: Right Knee Issue -- Mysterious injury, with knee hyperextending strangely...
Posted By: Michael Frind
Date: Saturday, 27 February 2010, at 7:16 p.m.
In Response To: Re: Right Knee Issue -- Mysterious injury, but more information needed first.... (AA)
Dear AA,
Since your response of February 1, have you managed to get the knee evaluated by an orthopedist?
Looking back at the signs and symptoms you noted, I think the single most worrisome one is that the knee is hyperextending abnormally. Such hyperextension can indicate ligamentous deficiencies (given that the ACL and PCL together play key roles in limiting how far the knee extends).
It is important to keep in mind that a small amount of hyperextension, generally a few degrees, is normal and is useful in locking the knee for purposes of standing. This can be termed anatomic hyperextension. Any such hyperextension more than a few degrees results in an increasing risk of ACL and PCL injury. But it is also important that the amount of anatomic hyperextension be the same in both knees. Any side-to-side discrepancy in knee range of motion will result in serious gait problems as well as other long-term issues. (This is why regainment of full range of motion is a high priority after any knee surgery.) If one knee suddenly starts extending (hyperextending) much further than the other, then that is a strong sign that serious ACL or PCL injury has occurred.
Weak hamstrings can also play a role in causing abnormal a amounts of hyperextension, and indeed it is possible for muscular weaknesses to enable knee-ligament injuries to occur. In terms of injury diagnostics, manual-manipulation tests can be done under anesthesia in order to rule out the possibility of leg muscles masking ligamentous issues. If the standard manual-manipulation tests (Lachmann drawer tests, anterior drawer test, posterior drawer test, as well as high-accuracy passive range-of-motion measuring) are inconclusive, then repeating all these tests under anesthesia should be considered.
The frightening aspect of excessive hyperextension (e.g. affected knee extending backwards much more than the unaffected knee) is that it can worsen on its own quite quickly. (Often, a hinged extension-limiting brace is recommended, and is set so that it limits the extension to that of what the uninjured knee has.)
By how much is your knee hyperextending (in comparison to the other knee, which we presume is uninjured) right now? Has there been a change in the past month?
Yours truly,
Michael Frind.
Knee Library http://factotem.org/library
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