For a brief overview of knee anatomy, physiology, and biomechanics, please click here.

For insight into nailing down a diagnosis for a meniscal injury in the absence of ligament tearing, and also for insight into tracing meniscal injuries to certain modes of forcing, please see the July 2006 article Meniscal Tear Characteristics in Young Athletes With a Stable Knee -- Arthroscopic Evaluation, in the Meniscal Injuries: Causes, Consequences and Treatments Subsection.

Magnetic Resonance Imaging Abnormalities in Symptomatic and Contralateral Knees: Prevalence and Associations With Traumatic History in General Practice, Simone S. Boks et al.; The American Journal of Sports Medicine, Baltimore; December 2006, Vol 34, pages 1984-1991. Comments: MRI (magnetic resonance, also known as nuclear magnetic resonance), which uses magnetic fields to excite hydrogen atoms in tissue, is an excellent tool for peering inside the knee noninvasively and without the dangers of ionizing radiation (as is used for standard X-rays and also CAT/CT scans). The latest MRI machines, using magnets of 3 Teslas or stronger, bring the sharpest images, although even a standard-issue 1-T machine can give excellent resolution of knee injuries. The problem with MRI scans is that they do not always reveal the full extent of knee-ligament injuries. But they provide a lot of insight, and are an excellent adjunct to the low-tech essential diagnostics of manual-manipulation testing and, of course, history-taking (i.e. gathering information on how the knee was injured, how it was forced, whether or not any loud noises were heard from the, whether or not it swelled up grotesquely, etc.). This study, done in Holland, found that comparing a recently-injured knee to the contralateral one provides helpful insight into whether certain MRI findings could be due to long-standing degeneration or old injuries.

Magnetic Resonance Imaging of Articular Cartilage -- Trauma, Degeneration, and Repair, Hollis G. Potter and Li F. Foo; The American Journal of Sports Medicine, Baltimore; April 2006, Vol 34/4. Comments: This article delves deeply into the fascinating topic of articular-cartilage diagnosis via MRI imaging. Note that MRI imaging has advanced considerably within the past few years, thus enabling a lot of information to now be gleaned noninvasively which in the past might have been available only through arthroscopy. Today, MRI imaging is available in a staggeringly huge number of variations, especially with regards to pulse sequences. Different pulsing techniques and new methods of data processing have brought tremendous capability and versatility to this already-very-impressive imaging tool. (The new techniques have also made it possible to avoid the concerns associated with injection of contrast agents into the joint space.) Newer, more-powerful MRI machines, especially the cutting-edge ones with 3-Tesla coils (compared to the average machines with 0.7T to 1T coils; note that 5T coils are under development as of this writing) bring razor-sharp resolution and therefore the ability to depict pinpoint detail impossible only a few years ago. As a result, the accuracy and usefulness of MRI diagnosis has improved significantly, especially when this tool is used by an experienced MRI radiologist who is up-to-date on the latest technological and diagnostic nuances.

Radiographs Are Not Useful in Detecting Arthroscopically Confirmed Mild Chondral Damage, Rick W. Wright et al.; Clinical Orthopedics and Related Research; January 2006, Vol 442, pages 245-251. Comments: This study shows that plain X-rays are not useful for ascertaining mild articular-cartilage damage (e.g. as present in chondromalacia).

Prospective Trial of a Treatment Algorithm for the Management of the Anterior Cruciate Ligament–Injured Knee, Donald C. Fithian et al.; The American Journal of Sports Medicine, Baltimore; March 2005, Vol 33, p. 335-346. Comments: This article clearly shows the behind-the-scenes thinking that occurs in the orthopedist's mind when deciding upon a recommendation for a given patient. If you find yourself wondering why your doctor has not recommended reconstruction for your severely damaged ACL, then this article will provide good insight for you. The study was funded by a well-known American HMO (health management organization), Kaiser Permanente. This company, like all private health insurers, has an extremely strong vested interest in minimizing current costs. Since such health insurance is typically contingent upon one's educational institution or employer, the HMO has no interest in long-term concerns (e.g. premature osteoarthritis precipitated by repeated giving ways of a chronically ACL-deficient knee), and thus focuses on trimming short-term costs (e.g. recommending that ACL reconstruction be only pursued for active athletes, recommending that no bracing or off-the-shelf bracing be used instead of custom-made bracing, and so on). When healthcare is privatized, decisions become business ones instead of human ones.

A Systematic Approach to Magnetic Resonance Imaging Interpretation of Sports Medicine Injuries of the Knee, Timothy G. Sanders and Mark D. Miller; The American Journal of Sports Medicine, Baltimore; January 2005, Vol 33/1, p. 131-148. Comments: This article provides a comprehensive and definitive overview of knee MRI-scan interpretation. Anyone who has undergone an MRI examination would be well-advised to obtain the complete set of scans (on CD) and review them. Interpreting MRI scans is a combination of art and science, and understanding the technical attributes and workings of MRI technology requires a reasonable understanding of physics. Granted, reading this article does not confer the extensive training and experience that a highly trained MRI radiologist would have, but taking the time to work through both this article and one's own MRI scans would prove valuable in that one could then see the basis of one's MRI report. Please bear in mind that MRI-scan images are typically cross-sectional slices. Therefore, a structure which happens to pass through a given imaging plane might appear strange merely because of the sharply oblique ankle at which the slice was taken. (It is also possible for the image to be distorted by slight movements of the patient during the imaging process, for example as a result of the patient coughing or sneezing. In such cases, the examination is usually redone. Other types of imaging artifacts are possible too, as the authors duly note.) Finally, keep in mind that it is possible for certain types of injuries to not appear on an MRI investigation; therefore, MRI results should be used in conjunction with other diagnostic avenues, including manual-manipulation testing (done under anesthesia, if inconclusive otherwise) and arthroscopic investigation.

Incidence and Location of Bone Bruises After Acute Posterior Cruciate Ligament Injury, Scott D. Mair et al.; The American Journal of Sports Medicine, Baltimore; October 2004, Vol 32, p.1681-1687. This article describes the occurrence of bone bruising in knees which have incurred PCL tearing. Note that bone bruising is also a very common accompaniment to ACL tearing. In essence, bone-bruising is a very forceful and violent crushing of the articular-cartilage-covered bone surfaces, resulting from the sudden smashing-together of the bones during an injury involving high kinetic energy. (Remember that kinetic energy increases with speed squared. As an example, if running speed is taken to be four times that of walking speed, then the injuries during direction changes will be 16 times as bad.) Bone bruises can engender pain for months on end, and technically do not heal. Rather, they sort of scar over, as the original hyaline articular cartilage is replaced with suboptimal fibrocartilage. (The underlying microtrabecular bone does not really recover from having been smashed up. If the crushing was severe, the contour of the articular surface is disrupted to the extent that surgical attempts at recontouring might be recommended.) Bone bruises are well-correlated with increased predisposition to osteoarthritis. Note that PCL injuries can occur via a variety of means, including posterior shearing (car-dashboard injury), injurious hyperextension, and hyperflexion, sideways forcing, and twisting. Meanwhile, ACL injuries can occur via sideways forcing, twisting, anterior shearing, and twisting. Clearly, there are many circumstances under which multiple ligaments can be injured. Although ACL and PCL injuries only occur simultaneously if the injury is extremely severe (e.g. total knee dislocation, as might occur in a motor-vehicle crash or a high-speed alpine-skiing incident), it is quite common to tear one of the cruciate ligaments in conjunction with a collateral ligament. The nature and extent of the ligamentous tears also gives insight into where bone bruising might be expected. Likewise, certain bone-bruising patterns tend to be indicative of which types of ligamentous injurious might be anticipated.

University of Minnesota, Sports Orthopedics Clinic, Knee Examination. Comments: This on-line resource includes a comprehensive description of how a knee is evaluated for cruciate-ligament injuries. Also present are short videos (viewable on Windows-based machines using freely available Windows Media Player; players for Unix/Linux and Macintosh machines are also available) which show the test being performed on normal and injured knees. (Note that the page linked to is only the first of a half-dozen; the links to the subsequent pages on the site are provided on each page.) Please keep in mind that even moderately tensed leg muscles can easily mask a torn cruciate ligament. To obtain reliably accurate results, it may be considered appropriate to perform these tests under anesthesia.

For insight into the inaccuracies that can creep into KT-1000/2000 testing (most notably as a result of the examiner being right-handed or left-handed, and therefore being more comfortable testing either the right or the left knee), see the October 2003 article Association of Menstrual-Cycle Hormone Changes with Anterior Cruciate Ligament Laxity Measurements, in the Female-Athlete Knee-Injury Incidence and Prevention Subsection.

Development and evaluation of an activity-rating scale for disorders of the knee , Robert G. Marx; The American Journal of Sports Medicine, Baltimore; Mar/Apr 2001, Vol 29/2, p. 213. Comments: This article discusses a knee-function classification system, and includes points on planning and presentation of knee-patient questionnaires. (This article is cross-listed under Evaluation of the Reconstructed Knee.)

Clinical Examination, Todd S. Ellenbecker; Knee Ligament Rehabilitation, edited by Todd S. Ellenbecker. Philadelphia, Pennsylvania: Churchill Livingstone (Harcourt), 2000. Pages 24-39. Comments: This article (book chapter) gives an excellent overview of the manual-manipulation tests which must be performed on a knee suspected of harbouring ligamentous injuries. Note that in cases where test results are inconclusive, the problem is often traceable to the masking effect of residual tenseness in the knee-surrounding musculature. Such tenseness is a common consequence of a knee-ligament injury, and (for testing purposes) can be alleviated by repeating the testing under anesthesia.

Instrumented Examination, Todd S. Ellenbecker; Knee Ligament Rehabilitation, edited by Todd S. Ellenbecker. Philadelphia, Pennsylvania: Churchill Livingstone (Harcourt), 2000. Pages 40-69. Comments: This chapter/article is a must-read for anyone who has been examined via knee-arthrometer instruments. Instruments are very helpful in providing reproducible measurements of knee laxity and hence injury to ligaments, but they must be used properly. The authors note that the person doing the examination must be well-experienced. (This caveat also applies to manual-manipulation tests, as done by hand by a seasoned orthopedic professional. Instruments such as those described in this chapter should only be used as an adjunct to manual-manipulation testing.) The most widely used device, the basic KT-1000/2000 from MedMetric, should only be considered accurate if the person doing the testing has had at least a month's worth of experience in using it. Similar precautions apply to other knee-ligament laxity testers such as the KLT, Genucom, Dyonics DCT, and UCLA-ICKTA devices. Meanwhile, a stationary dynamometer (e.g. Biodex, Cybex, Kin-Com), a sophisticated and highly automated machine which measures kinematic parameters and which very nicely quantifies strength and endurance, but does not directly measure knee-ligament laxity, can bring good accuracy and reproducibility without making a lot of demands on the clinician's skills. (Dynamometers are very expensive machines, and many take up a lot of space. The ones described herein are designed for durability and longevity. Properly maintained, these units can last for decades. The dynamometers described in this chapter date from the mid-1990s, and so the computerized aspects of the units specified will appear out-of-date today. However, the basic mechanical and electromechanical aspects will remain the same in newer units. Many dynamometers have been upgraded to reflect the ongoing advances in computer capabilities.) Newer devices, such as those involving force plates (e.g. from AMTI or Kistler) and three-dimensional optical-marker-tracking systems (e.g. from Northern Digital), are also helpful for ascertaining biomechanical parameters and for measuring rehabilitation progress and determining areas needing improvement. (Additional comments are provided with the article.)

Voluntarily-evoked positive Lachman test produced by gastrocnemius-muscle contraction: A report of three cases, Mitsuaki Noda; The American Journal of Sports Medicine, Baltimore; Nov/Dec 2000, Vol 28/6, p. 893. Comments: Noda discusses three cases in which ACL-injured people were able to simulate the Lachman test merely by tightening the gastrocnemius muscle group. (The Lachman test is the standard ACL-deficiency test, and it entails having the examiner pull forwards just below the knee, with the knee at about 30 degrees flexion. The Lachman test is only accurate if the hamstrings a completely relaxed during the test; if there is any doubt about hamstring tenseness, the test should be repeated under anesthesia.)

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