Magnetic resonance imaging was used to analyse the patellofemoral relationships during the first 3O' of knee fiexion in women with recurrent patellar dislocation. The patellofemoral joints were imaged both sagittally and axially with the knee flexed O , 1O , 200, and 3 O At the beginning of knee flexion the sulcus angle was greater than in unaffected women, the lateral patellofemoral angle was smaller, the patella displaced further laterally, tilted more laterally and the congruence angle was directed more laterally. At 34 O of knee flexion these differences were less marked than at O to 1O. Logistic regression analysis showed that the sulcus angle at 10' of knee flexion was the most diagnostic feature, indicating that there is an anatomical predisposition to recurrent dislocation and that pathological patellar tracking starts from the beginning of flexion. Traditional sunrise radiographic films taken at 25#{176} to 300 knee flexion clearly miss diagnostically important information.

The association between different knee exertion injuries and lower limb malalignments was studied in 121 male athletes with knee exertion injuries and in 20 male athletes without knee symptoms. The associations between different malalignments was also analyzed. Leg length inequality (LLI), knee valgus, and different indexes of patellofemoral joint congruence were measured using radiological methods. Male athletes with patellar apicitis (n = 59) had significantly more LLI (P less than 0.001) and patella alta (P less than 0.05) than athletes without knee symptoms. The knee valgus was of the same numerical value in the shorter and longer leg sides in subjects with LLI of at least 5 mm (n = 58). A positive correlation was found between lateral patellar displacement (LPD) and patella alta (LT/LP) (P less than 0.001). Negative correlations were found between the sulcus angle (SA) and the lateral patello-femoral angle (LPA) (P less than 0.001) as well as between the LPD and the LPA (P less than 0.001).

From a population of 1503 school children, 38 15-year-old children reporting recurrent or continuous low-back pain (LBP) and 38 asymptomatic controls (34 boys and 42 girls) matched for age, sex and school class, were compared with respect to spinal mobility and trunk muscle strength. The subjects were interviewed on leisure time physical activity preceding the measurements. Of the subjects with recurrent or continuous LBP and of those completely without LBP experience 73.7% vs 42.1% reported that they pursued some physical activity two days a week or less (P = 0.006). Further, decreased spinal mobility, diminished endurance strength of the back muscles and diminished dynamic strength of the abdominal muscles were found in the group with a low frequency of activity. Mobility in children pursuing physical activity two days a week or less was decreased in lumbar extension measured by flexicurve, in forward bending, in side bending and in straight leg raising. Our results indicate that a very low frequency of physical activity in the young might be the risk factor for LBP. Pursuing sports as a leisure time activity is not harmful; on the contrary it has positive effects on spinal mobility and trunk muscle strength.

Effect of patellar brace on patellofemoral relationshipsKoskinen SK, Kujala UM. Effect of patellar brace on patellofemoral relationships. Scand J Med Sci Sports 1991: 1: llP-122.The effect of patellar brace on patellofemoral relationships was analyzed using magnetic resonance imaging in 17 knees with patellar subluxation or dislocation. Images were produced in 0" and 20" knee flexions without the patellar brace, with patellar brace and with patellar brace after 1 h of walking. In knee extension, the patellar brace had an unfavorable effect on lateral patellar tilt, but decreased the tilt in 20" knee flexion. The excessive lateral patellar displacement was alleviated in both knee flexion angles. The corrected position was still apparent after physical exercise. Isometric quadriceps muscle contraction increased the displacement. These results suggest a positive stabilizing effect of the brace in patients with patellar instability.

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