Eighteen male patients who had untreated chronic ACL rupture were studied in order to evaluate thigh muscle size, morphology, and isokinetic performance of the quadriceps muscle. Computed tomography disclosed a 5.1% mean atrophy of the quadriceps (P less than 0.05), 2.1% slight hypertrophy of the hamstrings (P less than 0.05), and also nonsignificant changes of all other muscle areas of the injured thigh. Muscle morphology (m. vastus lateralis) was normal in 11 biopsy specimens, whereas minor abnormalities (irregular shape or hypotrophy) could be seen in the rest. Isokinetic mechanical output of the knee extensors was 71% to 87% of that of the noninjured limb (P less than 0.01), and the mechanical output corrected for differences in quadriceps cross-sectional area was significantly lower in the injured than the uninjured limb. As there were no significant correlations between isokinetic performance and muscle size or qualitative morphology or morphometric data, the strength decrease cannot be explained by muscle atrophy or structural changes per se. We conclude that nonoptimal activation of the muscles during voluntary contractions is probably the most important causative mechanism of the strength decrease found in patients who have chronic symptomatic ACL tear.

Snowboard injuries in a Swedish ski area were evaluated from 1989 to 1999. All injured skiers (alpine, telemark, snowboarders) who sought medical attention at the local Medical Center within 48 h of the accident, were asked to answer an injury form. Physicians assessed and treated the injured skiers. There were a total of 1775 injured skiers; 568 injured snowboarders mean age 19 years. The female/male ratio was 34/66%, the injury rate 3/1000 skier days, three times higher than that of alpine skiers. The skill level of the injured snowboard riders improved during the period. The fall/run ratio of the beginners was higher (1.0) and their risk behavior lower (3.9 on visual analogue scale 1-10) in comparison to the advanced riders (0.4 and 6.6, respectively). Injuries were in 54% located to the upper extremity, 35% were wrist/lower arm injuries. Beginners had significantly higher frequency of lower arm/wrist injuries (46%), than average (32%) and advanced riders (20%). The most frequent single diagnosis was wrist/lower arm fracture (20%). Advanced riders tend to have more head/neck injuries than beginners, 17% vs. 13% (NS). Thus, with elevated skill level the injury pattern changed. For injury prevention, wrist guards and helmets are recommended for snowboard riders.

Three-dimensional movements of the knees in 13 patients with unilateral old tears of ACLs were studied during extension. Roentgen stereophotogrammetric methods were used to measure tibial movements in the injured and the intact knees. Reduced internal rotation and adduction were recorded at the end of extension on both sides. The injured knees displayed increased anterior and distal displacements of the tibial intercondylar eminence. Abnormal tibial displacements in our patients indicate that the absence of the ACL is not completely compensated for during active extension past 30 degrees; close to the extended position, the tibial movements tend to normalize.

and the 3Department of Rheumatology, Sahlgren's Hospital, S-413 45 Gothenburg, Sweden SUMMARY The activity of superoxide dismutase isoenzymes was determined in knee joint synovial fluid from 21 patients with rheumatoid arthritis, nine patients with reactive arthritides, and from 17 patients before arthroscopy or arthrotomy for suspected meniscal or ligament injury (controls). Extracellular superoxide dismutase was the major isoenzyme and accounted for about 80% of the total superoxide dismutase activity in the controls. The pattern of the superoxide dismutase isoenzymes was significantly different in rheumatoid arthritis, extracellular (EC) superoxide dismutase being half, CuZn superoxide dismutase double, and the total superoxide dismutase activity a third lower than the activity in the synovial fluid of the controls. The superoxide dismutase activities were similar in synovial fluid from the controls and from the patients with reactive arthritides. The total superoxide dismutase activity was almost three times higher in control synovial fluid than in normal human plasma, but 300 times lower than in human tissues.

No abstract