The purposes of this multi-center study were: (a) to document the location and type of meniscal and chondral lesions that accompany anterior cruciate ligament (ACL) tears, and (b) to test for possible relationships between these lesions and patient age, time from initial injury (TFI), and sports level (i.e., recreation, amateur, professional, and national). The cases of 764 patients with ACL tears who underwent arthroscopy for the first time were retrospectively analyzed. The group included 684 males and 80 females of mean age 27 years (range 14-59 years). The mean TFI was 19.8 months (range 0.2-360 months). Eighty-seven percent of the group engaged in regular sporting activity. Thirty-seven percent had medial meniscal tears, 16% had lateral meniscal tears, and 20% had tears of both menisci. The most common tear types were longitudinal tears in the posterior and middle horns of both menisci. Tears of the lateral meniscus were more centrally located than those of the medial meniscus. Incomplete tears and radial tears were significantly more common in the lateral meniscus. Nineteen percent of the knees had one or more chondral lesions. Sixty percent of the chondral lesions were located in the medial tibio-femoral compartment. Patient age was statistically associated with presence of a medial meniscal tear, presence of a grade 3 or 4 chondral lesion, and presence of a complex tear of the medial meniscus. Sports level was not statistically related to any of the parameters studied. The odds of having a medial meniscal tear at 2 to 5 years TFI were 2.2 times higher than the odds in the first year post-injury, and the odds at >5 years were 5.9 times higher than at 0 to 12 months TFI. The frequency of lateral meniscal tear remained fairly constant at 2 years TFI. The odds of having a grade 3 or 4 chondral lesion were 2.7 times greater at 2 to 5 years TFI than they were at 1 year post-injury, and these odds increased to 4.7 when patients at >5 years TFI were compared to those in the 2 to 5 years category. Multivariate analysis demonstrated that TFI and age were equally important predictors of lateral meniscal tears and of grade 3 or 4 chondral lesions; however, TFI was the better predictor of medial meniscal tear.

We conducted this cadaveric study to define a biomechanical rationale for rotator cuff function in several deficiency states. A dynamic shoulder testing apparatus was used to examine change in middle deltoid muscle force and humeral translation associated with simulated rotator cuff tendon paralyses and various sizes of rotator cuff tears. Supraspinatus paralysis resulted in a significant increase (101%) in the middle deltoid force required to initiate abduction. This increase diminished to only 12% for full glenohumeral abduction. The glenohumeral joint maintained ball-and-socket kinematics during glenohumeral abduction in the scapular plane with an intact rotator cuff. No significant alterations in humeral translation occurred with a simulated supraspinatus paralysis, nor with 1-, 3-, and 5-cm rotator cuff tears, provided the infraspinatus tendon was functional. Global tears resulted in an inability to elevate beyond 25 degrees of glenohumeral abduction despite a threefold increase in middle deltoid force. These results validated the importance of the supraspinatus tendon during the initiation of abduction. Glenohumeral joint motion was not affected when the "transverse force couple" (subscapularis, infraspinatus, and teres minor tendons) remained intact. Significant changes in glenohumeral joint motion occurred only if paralysis or anatomic deficiency violated this force couple. Finally, this model confirmed that rotator cuff disease treatment must address function in addition to anatomy.

These results indicate that chronic knee pain modulates central motor control of an adjacent muscle.

In this cross-sectional study, sagittal knee laxity and isokinetic strength of knee extensor and flexor muscle groups were measured and differences related to leg dominance were evaluated. A total of 44 healthy male soccer players (who had trained regularly at least for the last five years) and 44 sedentary people as their control counterparts were involved in this study. All participants were tested using a KT-1000 knee arthrometer for knee laxity. Isokinetic concentric knee peak torque and hamstring/quadriceps (H/Q) ratio were also measured at 60, 180, 300 degrees/s through a Cybex 2 - 340 dynamometer. Posterior laxity in the non-dominant side of soccer players was significantly higher than in the dominant side (p < 0.005) while there were no significant anterior and total anteroposterior (total AP) laxity differences in both groups. Soccer players had significantly lower anterior and total AP laxity values than controls (p < 0.0001) while there was no significant difference between posterior laxity values in both sides. Dominant extremity demonstrated significantly higher knee flexor peak torque and H/Q ratio at 180 degrees /s in soccer players (p < 0.05). Similarly in sedentary controls, H/Q ratio at 60 degrees /s of the dominant side was significantly higher than that in the non-dominant side (p < 0.05). Soccer players had significantly higher extensor and flexor peak torque values and H/Q ratios than sedentary subjects for both extremities. In both groups, there were no significant correlations between knee laxity and isokinetic knee extensor and flexor strength and H/Q ratios except weak negative correlation between posterior knee laxity and isokinetic extensor peak torque at 60, 180 and 300 degrees /s (p < 0.005, r = - 0.43, p < 0.05, r = - 0.39, p < 0.05, r = - 0.32 respectively) in the non-dominant side of soccer players and at 300 degrees /s (p < 0.05, r = - 0.32) in the non-dominant side of controls. Soccer players demonstrated significantly less sagittal knee laxity and higher isokinetic strength of the knee flexors and extensors compared to sedentary controls. Isokinetic strength difference was found to be higher for the flexor muscle group. Further prospective studies are needed to explain whether the increased H/Q ratio decreases the risk of ligamentous injury.

In this study, the effect of dynamic stabilizers on the patellofemoral (PF) joint was investigated in normal volunteers (group I) and in patients with patellar pain (group II) or instability (group III) by using computed tomography (CT) analysis and integrated electromyography (iEMG) of the quadriceps muscle. Nine subjects (16 knees) from group I, 10 patients (12 knees) from group II and 8 patients (12 knees) from group III were included in the study. CT scans of the PF joint with quadriceps contracted (QC) and uncontracted (QU) and iEMG of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) were obtained with the aid of a specially designed jig at 0 degree, 15 degrees, 30 degrees and 45 degrees of knee flexion. The same muscle contraction pattern simulating closed kinetic chain exercise was used for both CT and iEMG. The difference between the congruence angles (CA) and tilt angles (PTA) in QC and QU positions and VMO:VL ratio from the iEMG were calculated separately for each flexion angle. CA was increased in all groups with quadriceps contraction at 0 degree and 15 degrees of flexion. PTA was decreased in group I and increased in groups II and III with quadriceps contraction at the same flexion angles. This difference was statistically significant in group III at 0 degree and 15 degrees of flexion. Quadriceps contraction did not affect the patellar position significantly even in the instability group at 45 degrees of flexion. In all flexion angles the balanced VMO:VL activity ratio was observed only in group I. In the other groups, VL activity was higher than VMO activity except at 45 degrees of flexion. These findings do not support the hypothesis of dominant centralizing effect of VMO on the patella in extension, but the effect of the VMO may be more clearly demonstrated by measuring PTA in both QC and QU positions.