Evaluation of knee stability and stabilizing systems.

Abstract

Knee injuries are a major problem in competitive contact sports. During the past two years, the Radiology Department and the Sports Medicine Section of Orthopedic Surgery have been evaluating knee stability before and after knee surgery. For this purpose, tape recording of television fluoroscopy has been used. As an outgrowth of the evaluation of injured knees, knee-stabilizing systems have also been investigated. Adhesive tape support of a conventional type and the knee “cages” and supports commonly used have been considered by some to add little stability and also to limit the mobility of the player. Athletes who had had previous injuries and who have “loose” knees at the present time were used as subjects. The normal and injured knees were examined in the usual manner but with television observation and recording. The medial and lateral collateral ligaments were tested in extension and in 15° of flexion. The examination is very easily conducted as shown in Figure 1. The cruciate ligaments are evaluated with pull and push pressure applied to the proximal tibia with the knee flexed to 90°. After a routine examination of the normal and “loose” knees, the following support systems were applied: 1. The conventional type of taping applied by a qualified athletic trainer. 2. A special type of taping for extra support using felt pads under the taping along the lateral margins of the knee, again applied by the trainer. 3. A “knee cage” which consists of a pair of pads above and below the knee tightly laced to the thigh and upper calf and connected by hinged metal side straps. Evaluation of the video tape recordings indicates that the instability in the athlete's injured knee was as marked with any of the stabilizing systems in place as without any support. We found that even a fresh stiff tape support gives no apparent stability to the knee. Tape support that has been in place during exercise limits normal motion only slightly and has no apparent stabilizing effect. It is worthy of note that the voluntary or involuntary contraction of the thigh muscles will markedly reduce detectable ligamentous laxity in a healthy young athlete. This is of importance in evaluation in the immediate period after knee injury, when severe spasm may occur. The spasm may obscure even severe ligamentous injury. It must also be said that we do not test the ligaments beyond the point of injury. The damage would occur in the range beyond where we can test. It is conceivable that stabilizing systems might add some support in the portion of the stress range that we cannot test. On the basis of our limited experience to date, the presently used supporting systems do not seem to provide any added stability to the knee in the range we can test. The apparent merit of taping is that it gives the athlete a sense of confidence, making him feel more secure. Our present diagnostic technics are inaccurate and subjective.