Purpose: The purpose of this study was to compare the clinical and radiographic outcome of arthroscopic partial and total meniscectomy.

Type of Study: Retrospective outcome study.

Methods: Thirty-six male patients with stable knees, no previous knee injury, and arthroscopic meniscectomy were matched into 2 groups: partial or total. In addition, a group of individuals with no known history of knee injury was matched to each patient with meniscectomy. All patients were re-examined by a clinical and radiographic examination 14 years after surgery.

Results: At follow-up, radiographic changes, including Fairbank changes and joint space narrowing, were seen in 6 of 18 patients (33%) after partial meniscectomy and in 13 of 18 patients (72%) after total meniscectomy (P < .05). Joint space narrowing >50% of the joint space was seen in 1 patient after partial meniscectomy but was present in 7 patients after total meniscectomy. In the healthy controls, 4 of 36 patients (11%) had radiographic changes but none had joint space narrowing. Fourteen years after surgery almost 70% of patients had a Lysholm score >94 (i.e., normal). Only 5 of 36 patients (14%) in the total meniscectomy group had knee symptoms during activities of daily living. A similar decline in activity levels according to Tegner was seen over time in the control group and in the 2 meniscectomy groups. Conclusions: The frequency of radiographic changes 14 years after meniscectomy is related to the size of the meniscus removed, but the grades of these changes are low and have little influence on activity and knee function.

Sagittal translation of the tibia was examined in a static test with 90 N force at 20°of knee flexion and dynamically during knee extension in a Biodex machine using increasing quadriceps torque in six healthy volunteers. The translation increased in a non-linear fashion with increasing torque. Similar relative increases in quadriceps torque caused similar relative increases in translation in the different individuals. The dynamic translation at the individual maximum quadriceps torque was equal to the static 90-N translation. There was a negative correlation between the maximum quadriceps torque and the static 90-N translation. The results indicate that the quadriceps torque is related to the amount of translation in the knee joint possibly by some feed back mechanism from the ligaments preventing abnormal translation. The findings also imply that a limitation of quadriceps torque around 80% of maximum would limit the strain in an injured ligament to a level not higher than what is caused by normal laxity measurements.

The incidence of femoral neck fractures in elderly people is rising requiring large health care resources. Internal fixation of the fracture is the treatment of choice in Scandinavia, but in 20-40% of the cases a late complication such as a segmental collapse of the femoral head after initial bone necrosis, or a non-union of the fracture because of non-healing, will occur. Because of the high disability associated with these local complications, revision surgery is needed, and in such a case the cost more than triples. Reduction of these local complications would avoid suffering and costs. The present study focuses on the analysis of technical principles for device design and internal fixation of femoral neck fractures, with the aim to reduce the number of local complications due to non-healing. The analysis is based on animal experiments, evaluation of patients who were treated with different internal fixation techniques, and finally biomechanical in-vitro tests of osteotomized femur specimens, which were stabilized wilh different internal fixation devices.

The results indicate that late complications are associated with early pronounced femoral shortening; monitoring of femoral length had, therefore, a high accuracy (92%) in predicting the late outcome. A shortening of more than 5 mm at one month predicted a greater lhan 6-fold increase of the incidence oflate complications. Use of a device that enabled a rigid osteosynlhesis reduced the incidence of non-unions, thereby reducing the overall local complication rate by one-third, and the need for revision surgery was halved. The rate of late segmental collapse, which occurred in 14-19%, remained independent of choice of device.

The healing of the fracture due to a stable fixation may accelerate the course to a segmental collapse in cases with initial osteonecrosis of lhe femoral head, due to vascular impairment at injury. Otherwise a stable fracture fixation, preventing a high postoperative deformation at the fracture site, was found to be a prerequisite for optimal fracture healing. Such a stable fixation can be optimally achieved with a device incorporating two or more threaded pins or screws, preferably cannulated, which are implanted With an a traumatic technique with high precision using guide systems to prevent unnecessary damage to bone. The optimal device for internal fixation of a femoral neck fracture should also have a good grip in osteoporotic cancellous ancl subchondral bone; the good grip of suitable threads may be enhanced by bone cement.

A complete rupture of the anterior cruciate ligament (ACL) results in static and often in functional instability. After an ACL-injury, most patients have to decrease their activity level, while some can cope with their injury and manage to keep a high activity level. A better tmderstanding of the influence of muscle activation and external load on the non-injured and injured knee, but also of the adaptive motion strategies employed by the patients with an unstable knee, is of importance for the construction of rehabilitation programs.

The general purpose of this thesis was to study certain knee motions during activities focused on rehabilitation, in individuals with anterior cmciate ligament injury and uninjured controls. The sagittal tibial translation and knee flexion angle were registered during motion with the CA-4000 computerized electrogoniometer and EMG was used for analysis of muscle activity. The injured knee had increased static laxity compared to the contralateral non-injured knee and the non-impaired group.

The amount of tibial translation increased with increased quadriceps torque during nonweight bearing activities (isokinetic and isotonic contractions). In the non-injured knees, the restraining mechanism was engaged above 50% of isokinetic concentric quadriceps torque and during the eccentric contractions already at low quadriceps torques (<10% of maximum). The motion pattern was similar in the injured knees and the amount of individual translation was larger during the eccentric contractions, compared to the non-injured knees.

During weight bearing, tibia translated anteriorly and remained in that position. In the non-injured knee, different loads and performance of weight bearing activities produced different amount of translation. Level walking and squat with the center of gravity behind the feet produced somewhat smaller amount of translations, while other weight bearing activities produced similar amount of translation compared to the non-weight bearing isotonic knee extension. In the injured knee, all weight bearing activities produced similar amount of translation, smaller compared to the non-weight bearing isotonic knee extension.

Quadriceps - hamstrings co-activation was not present during non-weight bearing quadriceps dominant activities and therefore, it was not shown to be a factor limiting anterior tibial translation. Also, during the weight bearing activities, hamstrings eo-contraction could not limit the anterior tibial translation. Quadriceps and gastrocnemius seems to work synergistically to stabilize the knee by maintaining an anterior position of tibia.

In the injured knee, isokinetic concentric quadriceps contraction below 50% of maximum torque produced the smallest amount of tibial translation. Weight bearing exercises produced similar ammmt of translation despite of load and performance, indicating that when level walking is allowed after an injury, other weight bearing activities can be performed without increasing the amount of translation. Eccentric isokinetic quadriceps contractions above 50% of maximum torque and isotonic quadriceps exercise with and without weights at flexion angles less that 40°, should be avoided in order protect the knee joint.

PURPOSE: The purpose of this study was to describe the sagittal tibial translation and EMG activity of muscles v. medialis and lateralis, gastrocnemius, and hamstrings, during common locomotion, in patients with an anterior cruciate ligament deficiency (ACL-def) and uninjured controls.

METHODS: In 12 ACL-def patients and 17 controls, sagittal tibial translation was registered with the CA-4000 electrogoniometer during level walking, cutting, and stair walking. Tibial position at each flexion angle was expressed relative to the femuro-tibial position at passive knee extension. EMG activity, measured with ME-4000, was normalized to the individual maximum isometric voluntary contraction for each muscle.

RESULTS: During the weight-bearing phase of motion, the tibia was anteriorly positioned in all legs. In the injured leg, the tibia translated more rapidly to an anterior position that was maintained for a longer time during the gait cycle. In the noninjured knees, motions with increased load lead to an increased anterior tibial translation in contrast to the injured knees, where the maximum displacement was already reached during level walking. The quadriceps and gastrocnemius muscles were simultaneously active during stance phase. Hamstrings were mainly active when the knee was close to extension and translation increased in spite of this activity.

CONCLUSIONS: The mechanism of the anterior positioning of tibia is qualitatively similar in the normal and the injured knee, but that position is obtained much further forward in the ACL deficient knee. Quadriceps and gastrocnemius muscles seem to work synergistically to stabilize the knee by maintaining the anterior position of tibia during weight-bearing motion. The role of hamstrings to restrict anterior translation is questioned.

The effect of increasing isokinetic, eccentric quadriceps torques on sagittal translation of the tibia was examined in six healthy volunteers and compared to the translation at 20° of knee flexion during a drawer test with 90 N force. The tibial translation increased in a linear fashion with a mean of 0.5 mm per 20% torque increase. In 20° of knee flexion, 10% of eccentric quadriceps peak torque consumed 80% of the anterior tibial translation induced by the 90 N Lachman test while eccentric quadriceps peak torque utilized 100% of the translation at the same test. The in vivo relation between muscle force and tibial translation is of importance in the treatment of patients with injury to the cruciate ligaments. The results indicate that an already low eccentric quadriceps torque causes a tibial translation that reaches the limit of the passive knee joint displacement where strain is assumed to develop in the anterior cruciate ligament. Already low eccentric quadriceps torque levels may therefore be harmful during rehabilitation after anterior cruciate ligament surgery.

Using electrogoniometry and electromyography, we measured tibial translation and muscle activation in 12 patients with unilateral anterior cruciate ligament injury and in 12 control subjects. Measurements were made during an active extension exercise with 0-, 4-, and 8-kg weights and during squats on two legs and on one leg where the projection of the center of gravity was placed over, behind, and in front the feet. In the uninjured subjects, tibial translation increased with increasing load except during the squat with the center of gravity behind the feet, which produced the smallest translation. For the active extension exercises, translation was greater during eccentric activity. In the anterior cruciate ligament-injured knees, all squats resulted in similar translation, which was smaller than that during the active extension exercise. The highest muscle activation was seen during squats. Hamstring muscle activity was low. Increased static laxity in the anterior cruciate ligament-deficient knee can be controlled during closed but not during open kinetic chain exercises. Coactivation of the quadriceps and gastrocnemius muscles seems to be important for knee stability, whereas hamstring muscle coactivation was insignificant. To minimize sagittal translation during nonoperative management of anterior cruciate ligament-deficient knees, closed kinetic chain exercises are preferable to open kinetic chain exercises, and importance should be attached to the spontaneous coactivation of the quadriceps and gastrocnemius muscles.

Study Design: Factorial quasi-experimental design.

Objectives: To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors.

Background: The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation.

Methods and Measures: Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60°•s-1), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject.

Results: The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group.

Conclusions: An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation.

Isolated partial rupture of the knee medial collateral ligament (MCL) is the most common traumatic knee ligament injury. Owing to the good short- and medium-term functional results after conservative treatment, this injury has been regarded as harmless. The outcome after combination injuries, with simultaneous rupture of the anterior cruciate ligament (ACL), is more uncertain.

The main purpose of this investigation was to improve the diagnosis of MCL injury and of concomitant injuries in acute knee trauma, in order to differentiate between the long-term effects of isolated and combined MCL injuries on knee function, sports participation, knee biomechanics and the development of secondary changes in articular cartilage and subchondral bone.

Magnetic resonance imaging (MRI) was used with the aim to replace arthroscopy in the diagnosis of acute knee injuries with hemarthrosis. In patients, knee function and stability were assessed 4 years following conservative treatment of isolated partial MCL injury, thus evaluating any residual biomechanical abnormalities that could influence the long-term prognosis. Further, the 10-year outcome after isolated partial MCL injury and combined MCL/ACL injuries was evaluated with special reference to knee performance, knee stability and the development of radiographic arthrosis. Secondary changes to articular cartilage and bone were further evaluated with MRI and analysis of proteoglycan fragment concentrations in joint fluid. Finally, the effects of removal of the MCL during postnatal growth on rat knee joint development were studied with special reference to bone apposition and cartilage changes.

Because of the low diagnostic accuracy for significant meniscal tears, MRI was not as reliable as arthroscopy for the diagnosis and screening of acute knee injuries. However, MRI was found to be superior to weight-bearing radiography and chemical analysis of joint fluid in the detection, staging, localisation and sizing of early articular cartilage changes in the knee joint.

In a 10-year perspective, partial MCL injury lead to a small, permanent increase in valgus rotation and decrease in initial valgus stiffness of the knee joint, but knee function and sporting performance were excellent. In 13% of the cases subtle radiographic changes (Fairbank signs) were present. Combined MCL/ACL injuries had a similarly good long-term functional outcome, in spite of a higher number of reinjuries, increased sagittal knee translation, and a higher incidence of subtle radiographic arthrosis (50%) than after an isolated injury. The animal experiment further suggested that a loss of the MCL during growth alters the bony development of the knee joint.

Intraarticular knee injuries, still are a challenge for proper treatment in Sports Medicine today .The increasing life expectancy as well as the patient expectation to maintain a sufficiant physical activity up to high ages gives the topic an increasing publicity. Still, the long tenn prognosis of the most conunon intraarticular knee injuries including cartilage injuries remaines unclear. The general purpose of this work was to investigate the long- term prognosis after common intraarticular knee injuries in respect to lrnee function, sports performance, knee stability and development of radiographical osteoarthrosis.

In this series, 221 patients were examined. The initial diagnosis in all cases was placed by manual examination under anesthesy and arthroscopy. The patients were reexamined at different long-term follow-up intervalls by an interview, including a subjective lmee score and an activity score, a thorough manual examination, and a radiographical examination including weight-bearing radiographs. In a part of the patients, a quality of life score was used.

Patients with isolated chondral damage in one knee had a good long-term functional' prognosis but developed mild to moderate signs of radiographical osteoarthrosis in the majority of the cases.

Complete ACL tears resulted in a permanent increase of sagittal knee translation no matter which initial treatment Injuries to knee joint cartilage or menisci or partial injuries to the ACL did not result in an increase of sagittal translation.

Radiographical signs for osteoarthrosis were encountered in 55 to 87% after different knee injuries, and seemed to advance slowly during the years.

Combined intraarticular knee injuries seemed to have a higher risk for development of radiographical osteoarthrosis than isolated injuries within the same time period.

Older age at initial diagnosis and treatment of an intraarticular knee injury is associated with a higher risk to develop radiographlcal osteoarthrosis.

After 12 to 20 years, patients with minor intraarticular knee injuries seem to have only a marginally better longterm prognosis for knee function and activity participation than patients with combined, major intraarticular knee injuries. However, the higher dissatisfaction with the results, the higher rate of symptoms and subsequent repeat surgery as well as the higher development of oeteoarthrosis during the years in the latter cases may point to that the risk for future lmee deterioration is greater after a combined than after a minor or/and isolated knee injury.

Subjective satisfaction and quality of life was high after a partial rupture of the ACL with minor concomitant injuries, and stayed unchanged over the years. In contrast, a complete rupture of the ACL did adversely influence quality of life, and subjective satisfaction with knee performance declined with time.

Increasing knowledge about the function of the meniscus and arthroscopy have made meniscus surgery more conservative. Arthroscopy was developed during the 70's and enabled the surgeon to select the most appropriate and tissue conserving therapy for a meniscus lesion. Arthroscopic meniscectomy and meniscus repair were introduced as new techniques for treatment of meniscus lesions.

This thesis comprises five long term follow-up studies of arthroscopic meniscectomy and open meniscus repair and one short term follow-up study of arthroscopic meniscectomy.

The long term follow-up studies include 152 patients, 113 with meniscectomy and 39 with meniscus repair, with stable knees, age less than 44 years and without preexisting gonarthrosis. All patients had a diagnostic at1hroscopy at the index operation and were evaluated clinically and radiographically 13-14 years after surgery.

At follow-up the frequency of radiographic changes was high but in general the radiographic changes were of a low grade. Only seven patients, 4 of 86 (5%) after partial meniscectomy and 3 of 27. (11%) after total meniscectomy fulfilled the criteria for gonarthrosis (minimal joint space less than 3 mm on radiographs and symptoms). More radiographic changes were found after total meniscectomy than after partial meniscectomy, meniscus repair or than in an un-injured control group. A similar rate of radiographic changes was seen when meniscus repair was compared to matched patients with partial and total meniscectomy. Knee function was in general good at follow-up and did not differ between patients with total meniscectomy and partial meniscectomy but patients with meniscus repair had a somewhat better knee function than a group of patients with partial and total meniscectomy. Cartilage fibril1ation present at meniscectomy did not influence the frequency of radiographic changes, knee function or activity at follow-up but older patients had more radiographic changes after meniscectomy than younger patients. The activity level decreased in a similar fashion over time after total meniscectomy, partial meniscectomy, meniscus repair and in un-injured subjects indicating that factors other than the knee injury and meniscus operation determines the decline in activity.

Thus, irrespective of meniscus treatment (arthroscopic partial/total meniscectomy and meniscus repair), in a 13-14 year perspective, the grade of radiographic changes in the knee joint were relatively low with no influence on activity and little influence on knee function.

In the short term follow-up study original data from patients with arthroscopic meniscectomy in the early 80' s when the technique was new was compared to similar data from patients operated today, when the technique is in routine use. The operation time was shorter and the frequency of subtotal meniscectomy was less today. In contrast to the early 80's the procedure is entirely out-patient. However, recovery and in particular return to sports were delayed today in comparison to previously.

A less supervised rehabilitation is suggested to be the main cause to the delayed recovery and a generosity with supervised rehabilitation after arthroscopic meniscectomy is advisable.

Sixty patients with stable knees and arthroscopic menisectomy were matched into two groups according to the presence of early degenerative changes at the operation. Patients with severe cartilage changes were excluded. The patients were between 20 and 40 years of age at the operation and no patient had previous surgery on the involved knee. The intraarticular findings were documented at surgery and the patients were re-examined 12 to 15 years after the meniscectomy. Pre-existing cartilage fibrillation at the meniscectomy did not seem to influence the long-term results. At the follow-up no difference was found between the groups at the physical examination, in subjective complaints, in knee function and activity or in radio-graphic findings. In the total group 62 % had early signs of arthrosis (Fairbank changes) and 42 % narrowing of the joint space (Ahlback grade 1-2) in the operated knee. No one had more severe changes. Radiographic signs of arthrosis were 4 times commoner in the operated knee compared to the non-operated kne after partial meniscectomy and 7 times commoner in the operated knee after subtotal meniscectomy. Arthrosis at the follow-up was seen three times more often in patients older than 30 years of age at surgery than in younger patients. The functional outcome was good and 70 % were still active in sports compared to 90 % before the operation.

We reexamined 43 patients with stable knees at a mean of 13 years after arthroscopic meniscectomy. The patients had a maximum age of 22 years at the operation and no patient had had previous surgery on the involved knee. At the follow-up examination, no differences in range of motion, muscle strength or tibial A/P displacement were seen between the operated and the nonoperated knees and 36 patients had no problem with their knee in daily life. Radiographic changes were found in the operated knee in 20 patients and in the nonoperated knee in 5 patients. 8 patients had a reduction of the joint space on the involved side, but none had more severe changes. Cartilage fibrillation at the index arthroscopy did not increase the radiographic changes at follow-up, but radiographic changes were commoner after subtotal meniscectomy (7/8) than after partial meniscectomy (17/35). These findings are similar to previous studies of arthroscopic meniscectomy of medium duration and do not differ considerably from studies of open meniscectomy.

We have followed for 13 years a consecutive series of 31 patients who had open repair of a torn meniscus. They were between 13 and 43 years of age at the time of operation and all had intact stabilising ligaments. Comparison was made with a matched group of normal subjects of similar age and level of activity.

The total rate of failure after meniscal repair was 29%; three of the repaired menisci did not heal and six reruptured during the follow-up period. At follow-up 80% of the patients had normal knee function for daily activities. Radiological changes were found in seven. Two had reduction of the joint space (Ahlbäck grade 1), one with successful and one with failed repair. In the control group of uninjured subjects one knee showed Fairbank changes but none had changes according to Ahlbäck. The incidence of radiological changes did not differ between the group with meniscal repair and the control group but knee function was reduced after meniscal repair (p < 0.001).

We conclude that the long-term results of meniscal repair in stable knees are good with nearly normal function and a low incidence of low-grade radiological changes.

Original data from 86 consecutive patients with arthroscopic meniscectomy 1980-81 was compared to similar data from 82 consecutive patients operated on 1995-1998. All knees were stable and without severe cartilage changes. In 1980 a follow-up examination was performed 10 (6-17) months after surgery and 1995 the patients answered two questionnaires 3 and/or more than 12 months after surgery. Age, sex and activity level before injury did not differ between the series and the distribution of meniscus tear types was similar.

In 1995 all patients were treated as outpatients while one third of the patients remained in hospital for 1-3 days in 1980. The operating time was shorter and the frequency of subtotal meniscectomy was less in 1995. Sick leave did not differ between the series and 2 out of 3 patients were back at work within one week. In 1995 almost half of the patients still had some knee problems 3 months after surgery but thereafter a substantial improvement was seen. The time to recovery was longer 1995 than in 1980. At the final follow-up the activity level and frequency of complete recovery did not differ between the series.

We conclude that the improved technique for arthroscopic meniscectomy during the last 15 to 20 years and less supervised rehabilitation has decreased the costs and freed resources for other patients. However, with the simplified rehabilitation, the previous opinion of a very fast recovery after arthroscopic meniscectomy has to be reevaluated.

This study investigated the long-term outcome of common meniscus treatment (meniscectomy, repair). A consecutive series of 30 patients with open meniscus repair were compared retrospectively to 30 patients who had an arthroscopic partial or subtotal meniscectomy. The groups were matched according to sex, age, meniscus lesion, and follow-up time. The patients were aged 13-43 years at the time of operation, all had intact cruciate ligaments, and none had had previous surgery on the knee. Patients were reexamined at a mean of 13 years after the operation. In addition, for a subgroup of 22 matched pairs, data were available from a 7-year follow-up. Four of the repaired menisci did not heal, and another three reruptured during the 13-year follow-up, these menisci were all excised (23%). Meniscal remnant surgery was needed in 6 cases (20%) after initial meniscectomy. At the 13-year follow-up there was no difference between the groups in knee function, subjective complaints, or manual findings. Almost 90% of the patients in both groups had no knee problems during daily activities. At the late follow-up radiographic signs for bone spurs, sclerosis, or flattening of the femoral condyle were found in around half of the cases in each group. Three patients (10%) with initial repair and 8 (27%) with meniscectomy had minor joint space reduction, but no patient had more severe radiographic changes. After 7 years (subgroup) joint space reduction was more common after initial meniscectomy than after repair (P < 0.05). After 13 years the incidence and severity of arthrosis did not differ significantly between the two groups, even when only the successful repairs were compared to meniscectomy (P = 0.06).

This study on human subjects, comprises of four cross sectional and one prospective cohort study. The general purpose of this work was to develop a technique for measuring in vivo, sagittal anterior-posterior translatory motions in the knee joint using a computerized electrogoniometer (CA-4000, OS Inc., Hayward CA, USA). Healthy human subjects served as controls while patients with arthroscopically confirmed unilateral ACL deficiency served as the experimental group.

The measurements were repeatable, accurate and valid. In all groups, as a consistent pattern, the tibia maintained an anterior position in relation to the femur during the load bearing phases and a posterior rosition in the non load bearing phases of step ascents and descents. Contraction of the gastro-soleus grour of muscles, before the lift off phase of ascent, resulted in an anterior positiOn of the tibia in relation to femur which was anterior to the posterior limit of static laxity testing. Step heights between 15 to 23 cm did not influence the amount of tibial translation.

During step ascent the amount of femoral roll-forward per degree extension was significantly smaller in the ACL deficient knees than the contralateral noninjured or healthy control knees.

ACL deficiency resulted in a larger than normal static space (125% to 257%) in the injured knees. It also resulted in an anterior shift of the tibia-femoral resting position of the injured knees.

The amount of the static laxity space the ACL deficient knee utilised during stair climbing varied, depending upon the knee flexion angle. Nearer to extension it was 90% and near to mid flexion (50°--{50°) it was 42% of the maximal static laxity space. In the conservatively treated ACL deficient group, the contralateral healthy knees showed 28% increase in the static AP laxity at follow up when compared to the index measurement and the control knees.

In the ACL reconstructed group, the increased static AP laxity and anterior shift of the tibia-femoral resting position in the reconstructed knees persisted at a minimum follow up of 21 months. Over the same period of time, the contralateral healthy knee also showed an anterior shift in the tibia-femoral resting position. The force at the anterior inflection point in static laxity testing, which was similar at index examination in both knees, diminished by 20% in the reconstructed knees at follow up.

The ACL plays an important role in optimally positioning the tibia-femoral articulation and maintaining the position during quadriceps and gastro-soleus muscle contraction.

Anterior cruciate ligament (ACL) injury causes long lay-off time and is often complicated with subsequent new knee injury and osteoarthritis. Female gender is associated with an increased ACL injury risk, but few studies have adjusted for gender-related differences in age although female players are often younger when sustaining their ACL injury. The objective of this three-cohort study was to describe ACL injury characteristics in teams from the Swedish men's and women's first leagues and from several European men's professional first leagues. Over a varying number of seasons from 2001 to 2009, 57 clubs (2,329 players) were followed prospectively and during this period 78 ACL injuries occurred (five partial). Mean age at ACL injury was lower in women compared to men (20.6 ± 2.2 vs. 25.2 ± 4.5 years, P = 0.0002). Using a Cox regression, the female-to-male hazard ratio (HR) was 2.6 (95% CI 1.4-4.6) in all three cohorts studied and 2.6 (95% CI 1.3-5.3) in the Swedish cohorts; adjusted for age, the HR was reduced to 2.4 (95% CI 1.3-4.2) and 2.1 (95% CI 1.0-4.2), respectively. Match play was associated with a higher ACL injury risk with a match-to-training ratio of 20.8 (95% CI 12.4-34.8) and 45 ACL injuries (58%) occurred due to non-contact mechanisms. Hamstrings grafts were used more often in Sweden than in Europe (67 vs. 34%, P = 0.028), and there were no differences in time to return to play after ACL reconstruction between the cohorts or different grafts. In conclusion, this study showed that the ACL injury incidence in female elite footballers was more than doubled compared to their male counterparts, but also that they were significantly younger at ACL injury than males. These findings suggest that future preventive research primarily should address the young female football player.

Football (soccer), the most popular sport worldwide, is associated with a high injury risk, and the knee joint is often affected. Several studies have found female players to be more susceptible to knee injury, anterior cruciate ligament (ACL) injury in particular, compared to their male counterparts. There is, however, some controversy regarding the magnitude of this risk increase and a few studies have found no differences. The influence of age and activity type on gender-related differences in injury risk is only scarcely investigated. In this paper, the literature reporting gender-specific ACL injury risk in football is reviewed. A literature search yielded 33 relevant articles that were included for review. These show that female players have a 2-3 times higher ACL injury risk compared to their male counterparts. Females also tend to sustain their ACL injury at a younger age than males, and a limiting factor in the existing literature is that age is not adjusted for in comparisons of ACL injury risk between genders. Furthermore, the risk increase in females is primarily evident during match play, but type of exposure is also rarely adjusted for. Finally, the studies included in this review share important methodological limitations that are discussed as a starting point for future research in the field.

Cartilage injuries are common in sports, and may on the long term develop to osteoarthritis. Prosthetic joint replacement is not satisfactory for young active individuals with extended cartilage injuries in large weight-bearing joints. In these cases, a treatment is needed which reestablishes normal joint surfaces by biologic means. Though different cartilage repair enhancing methods have been tried, up till now none of them has achieved regrowth of hyaline cartilage which duplicates the structure and functions of normal articular cartilage. More knowledge is needed to understand the response of articular cartilage to injury. Moreover, a better understanding of how articular cartilage develops may open ways to improve the repair response. The purpose of this work was to investigate maturation-related changes of articular cartilage during postnatal maturation, and to investigate the natural healing response to full-thickness cartilage injury as a function of maturation stage.

Physiologically, proteoglycan fragment concentrations in knee joint fluid decreased with maturation, and were inversely correlated with the maturation stage of the rabbits (r =- 0.69). The relatively high proteoglycan fragment concentrations in young animals might be the result of a higher turnover rate of proteoglycans in growing articular cartilage. The stiffness of articular cartilage in the rabbit knee joint decreased with maturation and was associated with an increase of subchondral bone volume fraction, and on the same time a substantial change in subchondral morphology. The results suggest that cartilage mechanics may also depend on the structural characteristics of subchondral bone.

Cartilage repair in young rabbits showed a faster filling of an osteochondral defect, and an earlier differentiation to hyaline-like cartilage than repairs in adult ones. The higher repair quality in young animals compared with the adults remained up to 48 weeks. Repairs in initially adolescent and adult animals showed furthermore signs of progressing degeneration between 12 and 48 weeks with decrease of the amount of hyaline-like cartilage in the tissue. However, irrespective of age, surface disruption of the repair was common, and no repair achieved regeneration to normal articular cartilage. The compressive stiffness of the repair tissues was always markedly softer compared with normal cartilage.

In preoperative joint fluid samples, TGF-ß1 decreased with maturation, and was moderately correlated with the proteoglycan fragment concentrations. Shortly after trauma, the concentrations of both substances were found increased, which was followed by a decrease up to 3 months, and then again an increase up to one year. However, meanwhile proteoglycan fragment concentrations had similar magnitude irrespective of age, TGF-ß1 concentrations never reached similarly high levels in adulthood as in infancy or adolescence. The cartilage adjacent to the defect had more signs for degeneration in younger rabbits. The similar patterns of TGF-ß1 and proteoglycan fragment concentrations during postnatal maturation may reflect the stimulatory effect of TGF-ß1 on proteoglycan synthesis. The higher TGF-ß1 concentrations in younger animals may be a reason for their better healing capacity, but also for their higher susceptibility to osteoarthritic change compared with the adult animals