The objective of this study was to quantify the coacti vation patterns of the knee flexor and extensor muscles as part of continued efforts to identify the role of the antagonist muscles in maintaining joint stability.The simultaneous EMG from the flexor and extensor muscles of the knee were recorded during maximal effort, slow isokinetic contractions (15 deg/sec) on the plane parallel to the ground to eliminate the effect of gravity. The processed EMG from the antagonist mus cle was normalized with respect to its EMG as agonist at maximal effort for each joint angle. The plots of normalized antagonist EMG versus joint angle for each muscle group were shown to relate inversely to their moment arm variations over the joint range of motion. Additional calculations demonstrated that the antago nist exerts nearly constant opposing torque throughout joint range of motion. Comparison of data recorded from normal healthy subjects with that of high perform ance athletes with hypertrophied quadriceps demon strated...

Muscular coactivation The role of the antagonist musculature in maintaining knee stability

Instrumented anterior/posterior laxity measurements were performed on 138 patients evaluated within 2 weeks of injury with their first traumatic knee hemarthrosis. All patients were tested with the MEDmetric Arthrometer model KT-1000 in a knee injury clinic. Seventy-five of the patients had knee arthroscopy. Thirty-three had arthrometer laxity tests under anesthesia. Eighty-seven percent of patients arthroscoped had anterior cruciate ligament (ACL) tears and 41% had meniscus tears. One hundred twenty normal subjects were tested to establish normal anterior laxity values. Three tests were used to evaluate anterior laxity: anterior displacement between a 15 and 20 pound force (compliance index), anterior displacement with a 20 pound force, and anterior displacement with a high manually applied force. Displacement measurements in normal subjects revealed a wide range of normal laxity with a small right knee-left knee difference. For example, the 20 pound anterior displacement range was 3 to 13.5 mm with a right knee-left knee difference (mean +/- SD, 0.8 +/- 0.7 mm). Eighty-eight percent of the normals had a right-left difference of less than 2 mm. In the 53 patients arthroscoped who had complete ACL tears, the anterior laxity measurements performed in the clinic were suggestive or diagnostic of pathologic anterior laxity in 50 patients.

Instrumented measurement of anterior knee laxity in patients with acute anterior cruciate ligament disruption

https://pure.tue.nl/ws/files/2305657/585371.pdf

The envelope of passive knee joint motion

One hundred nine patients over a 3 year period underwent reconstruction for chronic ACL ruptures using a freeze-dried, ethylene oxide-sterilized bone-patella tendon-bone allograft. Seven patients (6.4%) developed a characteristic persistent intraarticular reaction. This reaction was characterized by persistent synovial effusion with collagenous particulates and cellular inflammatory response. Synovial biopsies in all cases showed a similar chronic inflammatory process, characterized by fibrin, collagen, and phagocytic cells. The intraarticular white cells were predominantly lymphocytes. Removal of the allograft resulted in resolution of the reaction in all of the patients. Three of the seven patients showed HLA conversion. Gas chromatography demonstrated detectable levels of ethylene chlorohydrin, a toxic reaction product of ethylene oxide, within the allograft and synovium 14 months following implantation of one graft. These seven cases presented strongly suggest a nonspecific or immune mediated response that must be further delineated. The use of freeze-dried, ethylene oxide-sterilized allografts using standard techniques cannot be recommended for reconstruction of the ACL.

Intraarticular reaction associated with the use of freeze-dried, ethylene oxide-sterilized bone-patella tendon-bone allografts in the reconstruction of the anterior cruciate ligament

Thirty-five patients with documented absence of the anterior cruciate ligament were tested on the University of California, Los Angeles, instrumented clinical knee-testing apparatus and we measured the response curves for the following testing modes: anterior-posterior force versus displacement at full extension and at 20 and 90 degrees of flexion; varus-valgus moment versus angulation at full extension and 20 degrees of flexion; and tibial torque versus rotation at 20 degrees of flexion. Absolute values of stiffness and laxity and right-left differences for these injured knees were compared with identical quantities measured previously for a control population of forty-nine normal subjects with no history of treatment for injury to the knee. For both the uninjured knees and the knees without an anterior cruciate ligament, at 20 and 90 degrees of flexion the anterior-posterior laxity was greatest at approximately 15 degrees of external rotation of the foot. The injured knees demonstrated significantly increased total anterior-posterior laxity and decreased anterior stiffness when compared with the uninjured knees in all tested positions of the foot and knee. The mean increase in paired anterior-posterior laxity for the injured knees in this group of patients at +/- 200 newtons of applied anterior-posterior force was 3.1 millimeters (+39 per cent) at full extension, 5.5 millimeters (+57 per cent) at 20 degrees of flexion, and 2.5 millimeters (+34 per cent) at 90 degrees of flexion. The mean reduction in anterior stiffness for injured knees was also greatest (-54 per cent) at 20 degrees of knee flexion. Only slight reduction in posterior stiffness (-16 per cent) was measured at 20 degrees of flexion, and this probably reflected the presence of associated capsular and meniscal injuries. In the group of anterior cruciate-deficient knees, the patients with an absent medial meniscus showed greater total anterior-posterior laxity in all three positions of knee flexion than did the patients with an intact or torn meniscus. Varus-valgus laxity at full extension increased an average of 1.7 degrees (+36 per cent) for the injured knees, while varus and valgus stiffness decreased 21 per cent and 24 per cent. Absence of the medial meniscus (in a knee with absence of the anterior cruciate ligament) increased varus-valgus laxity at zero and 20 degrees of flexion.(ABSTRACT TRUNCATED AT 400 WORDS)

Measurement of knee stiffness and laxity in patients with documented absence of the anterior cruciate ligament

To determine whether any of the commonly used wiring techniques are rigid enough to allow early motion in the treatment of transverse fracture of the patella, the patellae of twenty-five fresh cadaver knees were fractured transversely and fixed using the following techniques: circumferential wiring, tension-band wiring, Magnusson wiring, and a modification of tension-band wiring. The knees were mounted in a machine capable of measuring quadriceps force, flexion angle, and fracture separation simultaneously. The knees were extended from 90 to zero degrees by applying tension to the quadriceps tendon with the force of gravity as the only resistance, and separation of the fracture fragments was measured first with the retinaculum unrepaired and then again with the retinaculum repaired. Separation of the fracture fragments was much less with the Magnusson wiring and modified tension-band wiring than with circumferential wiring or standard tension-band wiring. The retinacular repair was found to contribute to stability; however, this seemed most important in the less rigid repairs. We concluded that if early motion is to be used in treating transverse fractures of the patella, techniques in which the wire is anchored directly in bone should be used and the retinaculum should be repaired.

Efficacy of various forms of fixation of transverse fractures of the patella.

The anterolateral and anteromedial stability of seventeen fresh frozen cadaver knees was studied in a test apparatus designed to simulate physiological conditions. Statistically significant increases in internal rotation occurred in seven knees when only the anterior cruciate ligament was sectioned,

The role of incompetence of the anterior cruciate and lateral ligaments in anterolateral and anteromedial instability. A biomechanical study of cadaver knees

P McLeod

Papers

Efficacy of various forms of fixation of transverse fractures of the patella.

The role of incompetence of the anterior cruciate and lateral ligaments in anterolateral and anteromedial instability. A biomechanical study of cadaver knees

Efficacy of various forms of fixation of transverse fractures of the patella.