Joseph U. Barker, MD, et al.
Extra-Articular Mimickers of Lateral Meniscal Tears. In Sports Health. January/February 2011. Vol. 3. No. 1. Pp. 82-88.
This article was written to help the examiner recognise the subtle differences between intra-articular meniscal tears and extra-articular causes of lateral knee pain. The typical history, symptoms, and test findings are presented for each one.
Drawings, X-rays, and photographs are provided to help show each of these conditions and how they differ from a lateral meniscal tear. A brief review of the most common treatment for each condition is also offered. Since the treatment varies with each type of problem, an accurate diagnosis is needed to get these athletes back on their feet and in the game as quickly as possible.
Let’s take a quick look at each one. First and probably the most common condition to mimic a lateral meniscal tear is the iliotibial band syndrome (ITBS). This connective tissue structure runs along the entire outside of the thigh from hip to knee with several points where it inserts or connects to the knee.
Runners and cyclists have the most trouble with this problem because of the repeated knee flexion (bending) and extension (straightening). A special test called the Ober test is used to look for tightness of the iliotibial (IT) band.
X-rays don’t show positive findings for IT band problems. But they are used to look for tumors, arthritis, and fractures. MRIs are better at showing changes (e.g., thickening, fluid collection) in the connective tissue.
A second mimicker of a lateral meniscal tear is the presence of tibiofibular joint instability. The tibiofibular joint is along the outside of the knee where the tibia (larger of the two lower leg bones) connects to the fibula (smaller of the two lower leg bones).
Instability usually tells us the joint is loose or shifts either into subluxation (partial dislocation) or into a fully dislocated position. This can be caused by small but significant anatomic variations.
Even slight changes that alter the natural angle of this joint can allow the fibula to slip out of the groove that holds it in place. Or a traumatic injury damaging ligaments and connecting soft tissue can damage the joint resulting in the same type of instability.
Instability may keep the athlete from putting weight on that leg. The examiner compares the unaffected knee to the painful one and looks for changes in how the joint moves. Any unnatural shifts in the fibula as it moves against the tibia (called joint translation) will be evaluated with more specific tests (e.g., apprehension test, Radulescu test).
The third extra-articular source of lateral knee pain comes from snapping tendons. Tendons that insert into the fibula near the knee may slip back and forth over the bone causing a painful snapping sensation.
The symptom is most noticeable during knee motion. A larger than normal fibular head (round top of the fibula) can contribute to the problem. Sometimes releasing the tendon surgically and/or removing some of the bone and reshaping the fibular head are necessary to end the problem.
And finally, the common peroneal nerve located along the outside of the knee and lower leg may be irritated either from compression (pinching) or neuritis (nerve inflammation). Like all the other problems discussed nerve compression or inflammation can cause lateral knee pain. With nerve involvement, there are usually sensory (numbness, tingling) and/or motor changes (muscle weakness) to help direct the examiner in finding the problem.