Mean Knee Flexion Angle Research Articles

Inter- and intra-rater reliability of knee flexion angle measurements on X-ray and MRI.

Range of motion (ROM) is an important aspect of orthopaedic patient assessment. It can be measured at the knee joint by determining the knee flexion angle (KFA) a patient can achieve at extremes of flexion and extension. As with any measurement, the accuracy and reliability of the method used determine its validity. The consistency of magnetic resonance imaging (MRI) scans as compared to the current gold standard of X-ray remains unknown in terms of KFA evaluation. The aim of this study was to assess and compare the reliability of measuring KFA between X-ray and MRI scans. This study included 80 patients (94 knees) who had attended a specialist knee clinic due to varying knee pathologies and undergone both X-ray and MRI scans. Lateral and T1-weighted sagittal imaging views (respectively) were used to measure KFA by two trained observers independently at two separate time points, 8 weeks apart. The data was then statistically analysed and intra- and inter-observer reliability calculated using the intraclass correlation coefficient (ICC). The intra-observer reliability for X-ray was 0.96 (P<0.001) and that for MRI was 0.83 (P<0.001). The inter-observer reliability for X-ray was 0.99 (P<0.001) and that for MRI was 0.81 (P<0.001). All the intra-class correlation coefficients were graded as excellent in both the intra- and inter-observer reliability analysis. Overall, the mean KFA was notably higher on X-ray measurements than that on MRI scans. There was a statistically significant difference between Time 1 and Time 2 measurements (17.7° vs. 16.8°) for MRI data (P=0.022). No significant difference was found for X-ray measurements (46.4° vs. 45.6°) in this regard (P=0.182). Both X-ray and MRI allow KFA to be measured with an excellent degree of reliability. However, X-ray measurements were overall superior to that of MRI mainly due to the larger field of view of the visible on-screen image which more readily identifies the anatomical landmarks required to measure KFA.

Different squatting positions after total knee arthroplasty: A retrospective study

BACKGROUNDTotal knee arthroplasty (TKA) has been shown to improve quality of life and reduce pain. High-flexion activities such as squatting, kneeling, and floor transfers are mainly listed as demanding tasks. Among them, squatting is an important position.AIMTo provide a new squat position classification and evaluate the different squatting positions of a series of patients after primary TKA.METHODSFrom May 2018 to October 2019, we retrospectively reviewed 154 video recordings of the squatting-related motions of patients after TKA. Among the included patients, 119 were women and 35 were men. Their mean age at the index surgery was 61.4 years (range, 30 to 77).RESULTSThe median follow-up was 12 mo (range, 6 to 156 mo). We classified those squatting-related motions into three major variations according to squatting depth: Half squat, parallel squat, and deep squat. The angles of hip flexion, knee flexion, and ankle dorsiflexion were measured in the screenshots captured from the videos at the moment of squatting nadir. A total of 26 patients were classified as half squats, 75 as parallel squats, and 53 as deep squats. The angles of hip flexion, knee flexion, and ankle dorsiflexion all differed significantly among the three squatting positions (P < 0.001). In the parallel squat group, the mean knee flexion angle (°) was 116.5 (SD, 8.1; range, 97 to 137). In the deep squat group, the mean knee flexion angle (°) was 132.5 (SD, 9.3; range, 116 to 158).CONCLUSIONAmong the three squatting positions, deep squat showed the highest hip, knee, and ankle flexion angles, followed by the parallel squat. With the improvement of squatting ability, the patient's postoperative satisfaction rate was also significantly enhanced. However, the different squatting abilities of the patients cannot be effectively distinguished from the scoring results (P > 0.05). Our squatting position classification offers a pragmatic approach to evaluating patients’ squatting ability after TKA.

The Reversed Dynamic Patellar Apprehension Test (ReDPAT) mimics anatomical complexity in lateral patellar instability

Aims and Objectives: To develop a dynamic physical examination test that functionally simulates actual patellar instability events and that mimics the range of patellar stabilizer insufficiency in an individual patient. Materials and Methods: Seventy-four consecutive patients (male/female 33/41; mean age 22±7 years) with recurrent lateral patellar instability and thirty controls (male/female 16/14; mean age 31±14 years) were prospectively evaluated using the reversed dynamic patellar apprehension test (ReDPAT). The examination starts with the knee flexed at 120°. The knee is then extended while the patella is translated laterally. The maneuver is stopped at first onset of a subjective apprehensive reaction, and the ReDPAT result is considered positive according to this knee joint flexion angle. Anatomical predisposition was assessed according to Dejour’s classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, and varus/valgus malalignment. Results: The study group had an average of 3.4 ± 1.0 (1-6) anatomical risk factors for lateral patellar dislocation. Severe trochlear dysplasia (84%) and patella alta (49%) were the most common. Test sensitivity, specificity, and accuracy reached 97.3%, 90%, and 95.2%, respectively, and test-retest reliability was good (Pearson’s r 0.84; p&lt;0.0001). The ReDPAT results became positive at a mean knee flexion angle of 58°±17° (20°-90°). Knee flexion angle correlated significantly with the severity of trochlear dysplasia (p=0.018), valgus deformity (p=0.011), and the total number of anatomical risk factors (p=0.02). Conclusion: This study introduced the reversed dynamic patellar apprehension test as a reliable clinical examination tool in the assessment of lateral patellar instability. The results of this study indicate that the degree of knee joint flexion at which the provocative sense of apprehension becomes positive correlates with severity of trochlear dysplasia, valgus deformity and the total number of anatomical risk factors for patellar instability.

Tibial Tubercle Proximalization: A Novel Technique to Lengthen the Extensor Mechanism in Skeletally Mature Patients With Lateral Habitual Patellar Dislocations.

Background:A habitual patellar dislocation (HPD) is a rare condition in skeletally mature patients, especially for those with severe quadriceps contracture. Until now, no study has reported the effectiveness of tibial tubercle proximalization to lengthen the extensor mechanism in treating severe HPDs in skeletally mature patients.Purpose:To describe a novel comprehensive procedure that includes tibial tubercle proximalization, extensive lateral release, tibial tubercle medialization, and medial patellofemoral ligament (MPFL) reconstruction in treating severe HPDs in skeletally mature patients and to report its early clinical outcomes.Study Design:Case series; Level of evidence, 4.Methods:From January 2014 to May 2016, a total of 43 consecutive patients (47 knees) with HPDs were surgically treated at a single institution and were retrospectively reviewed. Among them, 11 skeletally mature patients (11 knees) with severe primary HPDs underwent the index comprehensive procedure. Results of patellar tracking were recorded preoperatively and at the final follow-up. The radiological assessment included radiographs in standard anteroposterior, true lateral, and axial views and computed tomography scans at full knee extension before surgery and at the final follow-up. Subjective patellofemoral function was evaluated with the Kujala functional score before the index procedure and at the final follow-up visit.Results:The 11 included patients were evaluated for a mean period of 34.9 months (range, 25-46 months). The mean knee flexion angle when the patella dislocated laterally was 25° (range, 10°-30°) preoperatively. Radiologically, there was a statistically significant improvement in the congruence angle, from 73.4° ± 17.0° preoperatively to –7.1° ± 5.8° postoperatively (P < .01) and in the lateral patellofemoral angle, from –65.6° ± 9.4° preoperatively to 6.1° ± 2.7° postoperatively (P < .01). The mean preoperative Kujala functional score was 42.9, and the mean postoperative Kujala functional score was 95.2 (P < .05). No patients reported a recurrence of patellar dislocation at the final follow-up visit.Conclusion:The novel comprehensive procedure, including tibial tubercle proximalization, extensive lateral release, tibial tubercle medialization, and MPFL reconstruction, effectively treated lateral HPDs in skeletally mature patients with severe quadriceps contracture.

The reversed dynamic patellar apprehension test mimics anatomical complexity in lateral patellar instability

To develop a dynamic physical examination test that functionally simulates actual patellar instability events and that mimics the range of patellar stabilizer insufficiency in an individual patient. Seventy-eight consecutive patients (male/female 35/43; mean age 22 ± 7years) with recurrent lateral patellar instability and 35 controls (male/female 16/19; mean age 31 ± 14years) were prospectively evaluated using the reversed dynamic patellar apprehension test (ReDPAT). Anatomical predisposition was assessed according to Dejour's classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, and varus/valgus malalignment. The study group had an average of 3.4 ± 1.0 (1-6) anatomical risk factors for lateral patellar dislocation. Severe trochlear dysplasia (84%) and patella alta (49%) were the most common. Test sensitivity and specificity was 93.7% (95% CI 0.8584-0.9791) and 88.2% (95% CI 0.7255-0.9670), respectively. The positive predictive value reached 94.9% (95% CI 0.8739-0.9859) and the negative predictive value was 85.7% (95% CI 0.6974-0.9519). The ReDPAT results became positive at a mean knee flexion angle of 58°±17° (20°-90°). Knee flexion angle correlated significantly with the severity of trochlear dysplasia (p = 0.018), valgus deformity (p = 0.011), and the total number of anatomical risk factors (p = 0.02). This study introduced the reversed dynamic patellar apprehension test as a reliable clinical examination tool in the assessment of lateral patellar instability. The results of this study indicate that the degree of knee joint flexion at which the provocative sense of apprehension becomes positive correlates with severity of trochlear dysplasia, valgus deformity and the total number of anatomical risk factors for patellar instability. This test indicates the patient-specific end of stable patellar tracking and the beginning of patellar stabilizer insufficiency. Therefore, this test might be helpful in deciding for or against a bony procedure in the treatment of patellar dislocation. II.

Effects of gracilis tendon harvest on in vivo knee joint kinematics

Aims and Objectives: The gracilis tendon is a commonly used autologous tendon graft in orthopedic surgery (e.g. anterior cruciate ligament (ACL), medial patellofemoral ligament (MPFL) or chronic acromioclavicular joint (ACJ) reconstruction) but also for example in anal incontinence surgery for formation of a neosphincter. In previous studies the effects of gracilis tendon harvest were analyzed after ACL rupture, its reconstruction and rehabilitation. However, all of these three incidents influence the outcome. Thus, the purpose of the present study was to evaluate the effect of isolated gracilis tendon harvest from uninjured knees on knee kinematics during daily activities. Materials and Methods: Patients between 18 to 60 years with harvest of their gracilis tendon for reconstruction of the ACJ were included. Exclusion criteria were previous surgeries or injuries of their knees. Knee kinematics were evaluated during gait analysis using an infrared optical motion capture system with 10 cameras (T20 S cameras, Vicon, Oxford, United Kingdom) and reflective skin markers. A set of 59 markers was attached on anatomical landmarks of the patients’ lower extremities, pelvis, spine and shoulders with double-sided tape. The position of these markers was tracked at 120 Hz during the trials. Daily activities such as walking and running were performed. Additionally, kick-backs were performed to analyze maximal active knee flexion an important function of gracilis muscle. To quantify the tibiofemoral motion and reduce soft tissue artifacts, the OSSCA (OCST, SARA, and SCoRE combined approach) technique was used. (Boeth 2013) The D’Agostino&Pearson Test was used to test for a Gaussian distribution. For parametric data the dependent t-test, otherwise the Wilcoxon test was used. Results: Sixteen patients were evaluated. However, four had to be excluded after MRIs showed an accidental harvest of the semitendinosus tendon. The mean age was 43 years [standard deviation (SD) 13 years] and time to follow up was 44 months (SD 25). The affected limb showed an increased abduction of 1,38° (SD 4,05; p=0,31) during walking and 0,65° (SD 5,23; p=0,70) during running, as well as an increased rotational translation of 2,26 mm (SD 3,62; p=0,08) during walking and 1,38 mm (SD 3,27; p=0,21) during running. The mean anterior-posterior translation was larger for the healthy limb with 1,15 mm (SD=5,30; p=0,08) during walking and with 2,43 mm (SD=5,99; p=0,23) during running. A larger mean knee flexion angle was measured for the healthy limb during walking, running and kick-backs (mean difference during walking: 3,05°; SD=7,15; p=0,28; running: 2,39°; SD=7,34; p=0,33; kick-backs: 5,31°; SD=8,59; p=0,10). However, none of these results reached statistical significance. Conclusion: These results show that gracilis tendon harvest in healthy knees does not lead to altered knee kinematics. However, the small size of our cohort should be taken into consideration. These data support the use of the gracilis tendon as autologous graft for reconstructive surgery.

Kinematic analysis of pressing situations in female collegiate football games: New insight into anterior cruciate ligament injury causation.

The most common events during which anterior cruciate ligament (ACL) injuries occur in football are pressing situations. This study aimed to describe the knee and hip joint kinematics during pressing situations in football games to identify kinematic patterns in actions with a high risk for ACL injuries. We filmed 5 female collegiate football matches and identified 66 pressing situations. Five situations with a large distance between the trunk and foot placements in the sagittal plane were analyzed using a model-based image-matching technique. The mean knee flexion angle at initial contact (IC) was 13° (range, 8°-28°) and increased by 11° (95% confidence interval [CI], 3°-14°) at 40ms after IC. As for knee adduction and rotation angles, the knee positions were close to neutral at IC, and only minor knee angular changes occurred later in the sequences. The mean hip flexion was 25° (range, 8°-43°) at IC and increased by 22° (95% CI, 11°-32°) after 100ms. The hip was also externally rotated by 7° (range, -19° to 3°) at IC, and gradually rotated internally, reaching 10° of internal rotation (range, -5° to 27°) at 100ms after IC. This study suggests that the observed knee valgus, internal hip and knee rotation, and static hip flexion previously reported in non-contact ACL injury events are unique to injury situations. In contrast, neither rapid knee valgus nor increased internal rotation was seen in non-injury pressing maneuvers.

Does instructional video footage improve tackle technique?

There is a high incidence of injury during rugby tackling. Tackle biomechanics are linked to this injury risk. The effectiveness of educational methods in teaching safe rugby tackling for players of various ages and experience levels has not been elucidated. We hypothesized that watching an educational video on rugby tackling technique would alter lower extremity kinematics and reduce cervical spine and head acceleration during tackling. Kinematics and kinetics of 50 collegiate and high school-aged rugby players were recorded while tackling an opponent in a laboratory setting. Movement of the lower extremity, upper body, and head were quantified with a motion analysis system. Participants were shown video instruction on tackling technique then performed another series of tackles. Data were compared pre- and post-educational intervention. A fixed effects model was used to compare the effect of repetition versus educational intervention. Skilled collegiate players tackled with significantly greater mean knee flexion angle post-educational intervention relative to pre-instruction, indicative of better technique. The fixed effects model indicated that video instruction decreased acceleration by a mean 51.8 m/s2 in collegiate players. However, the effect of repetition was shown to increase peak acceleration by a mean 11.2 m/s2. In contrast, the educational intervention resulted in an increased acceleration of 15.4 m/s2 for high school players, but the effect of repetition was shown to decrease acceleration by a mean of 5.2 m/s2. Experienced players respond as expected to video instructional intervention. Repetition may be more important for younger rugby players to learn effective tackling.

KINEMATIC ANALYSIS OF PRESSING MOVEMENTS IN WOMEN'S SOCCER COMPETITIONS

BackgroundThe most common movements that occur during anterior cruciate ligament (ACL) injuries in soccer are “pressing” movements. There are currently no accurate kinematic descriptions of joint kinematics in pressing movements...

Does Residual Varus Alignment Cause Increasing Varus Laxity at a Minimum of Five Years After Total Knee Arthroplasty?

BackgroundThe purpose of this study is to investigate whether varus-valgus laxity of cruciate-retaining (CR) total knee arthroplasty (TKA) changes between 1 year and >5 years after surgery based on postoperative limb alignment. MethodsOne hundred twenty-one varus osteoarthritic knees that underwent CR TKA were included. The minimum follow-up was 5 years. Weight-bearing full-leg radiographs were obtained postoperatively and the hip-knee-ankle (HKA) angle was measured. Knees were grouped in varus (HKA angle ≤ −3°, 47 knees) and neutral groups (−3° < HKA angle < 3°, 70 knees). The range of motion was measured and a Hospital for Special Surgery score was obtained at the last follow-up. Varus-valgus laxity at 15° of knee flexion was measured with stress radiographs after 1 year and at the last follow-up. ResultsNo knees required revision surgery. The mean knee flexion angle (121.0° vs 117.1°) and Hospital for Special Surgery score (90.3 vs 90.4) at the last follow-up were not significantly different between the varus and neutral groups. In both groups, there was no significant change in varus or valgus laxity between 1 year and at the last follow-up. ConclusionPostoperative residual varus limb alignment did not lead to increasing varus laxity after CR TKA in the mid-term.

Autologous morselised bone grafting for medial tibial defects in total knee arthroplasty.

To evaluate the outcome of autologous morselised bone grafting for a medial tibial defect of ≥10 mm deep in 45 total knee arthroplasties (TKAs). 38 patients aged 46 to 85 (mean, 73) years underwent 45 TKAs and autologous morselised bone grafting for a medial tibial defect of ≥10 (range, 10-25) mm in depth by a single surgeon. In the first 19 TKAs, 2 resected subchondral bone plates from the lateral tibial plateau were driven into 2 gutters made on the floor of the medial tibial defect as bony support posts. Morselised cancellous bone grafts were then impacted around these posts. In the remaining 26 TKAs, multiple drill holes were made on the floor of the defect to decrease the remodelling time. Morselised cancellous bone grafts were impacted to fill the defects. The tibial components were fixed with cemented (n=34) or non-cemented (n=11) technique. Internal fixation devices were not used; stem extension was used in only 2 TKAs (in a patient with Charcot joint and a patient undergoing revision TKA). After a mean follow-up duration of 65 (range, 24-174) months, no patient showed gait disturbance. The mean knee flexion angle was 113.8º (range, 90º-130º). No absorption or collapse of the grafted bone, or component loosening were noted on radiographs. The grafted bone completely incorporated into the host bone, with bony trabeculae crossing the interface within 2 years in the first 19 TKAs and within one year in the latter 26 TKAs. The margin of the grafted area resembled bony cortex in 30 TKAs. Autologous morselised bone grafting is a viable option for most medial tibial defects during TKA.

Comparison of knee kinematics between meniscal tear and normal control during a step-down task

BackgroundDifficulty descending stairs is a common functional complaint reported by patients with meniscal tears. Abnormal knee movement patterns, such as dynamic valgus of the knee or decreased knee flexion during step down, have been reported by clinicians, but 3D knee kinematics descending stairs has never been described in this population. ObjectiveThe objective of this study is to compare 3D knee kinematics of individuals with a meniscal tear to that of control individuals during a step-down task. MethodsTen participants (6 men and 4 women) diagnosed with a meniscal tear and eleven healthy participants (3 men and 8 women) were recruited. Three-dimensional knee kinematic data were recorded during five step-down task trials with a VICON™ motion analysis system. The following parameters were extracted from the stance phase period only: maximum angle, minimum knee angle, and range of motion (maximum minus minimum) values for sagittal, frontal, and transverse planes. A group comparison was performed by ANOVA using the velocity of the step-down task as the control variable. FindingsSignificant reductions in the mean maximum knee flexion angle, knee flexion/extension range of motion, and knee abduction/adduction were observed among the participants with a meniscal tear compared to the control group (mean differences and P values were 4.7°, P=0.02; 5.4°, P=0.02 and 1.6°, P=0.03 respectively). Differences in rotation movement were not significant. InterpretationThis study is the first to describe and compare 3D knee kinematics of persons with a meniscal tear during a step-down task. These findings support that significant kinematic changes occur in the sagittal and frontal plane in individuals with a meniscal tear compared to normal controls.

Predictors of flexion using the rotating concave-convex total knee arthroplasty: preoperative range of motion is not the only determinant.

The range of motion achieved after a total knee arthroplasty (TKA) affects many daily activities and overall patients' satisfaction. This study aims to define the determinants affecting post-operative midterm active flexion according to a specific cruciate-sacrificing prosthesis, the rotating concave-convex (ROCC(®)) TKA. Four hundred and eighty-four consecutive patients (584 TKAs) were prospectively followed. After baseline patient demographics and anatomical characteristics, clinical and radiological post-operative assessments were periodically recorded. The rotational alignment of the femoral component was additionally reported for 120 patients. Eligibility for final inclusion was a minimum of 5-year follow-up. Univariate analyses followed by a multivariate model were fitted to determine the independent predictors of midterm active knee flexion. Thirty-four TKA (5.8%) were excluded for a secondary surgery before their 50 years, 69 patients died (11.8%), and 21 (3.6%) were lost to follow-up. Overall, 460 TKAs were included. The post-operative mean knee flexion angle was measured at 127.7° ± 9.3°. Significant factors affecting final flexion under univariate analyses were the patient height and body mass index, the absence of previous surgery, a depressive state, the preoperative flexion angle, a preoperative flexion contracture, a patellar residual subluxation, the reconstructed patellar height, and the rotation of the femoral component. The multivariate model confirmed the patient's height, a depression, the preoperative flexion angle, a patellar residual subluxation, and the patellar height as statistically significant determinants. Aside from the preoperative flexion angle, numerous predictors of flexion, both patient- and procedure-related were identified. Surgeons should take these into account both when adequately informing their patient before surgery and when performing the arthroplasty itself. Prognostic, Level II.

In Vivo Movement of Femoral Flexion Axis of a Single-Radius Total Knee Arthroplasty

The objective of this study was to investigate in vivo femoro-tibial motion using the movement of femoral flexion axis of a single-radius TKA. We examined 20 clinically successful knees with a single-radius posterior stabilized TKA to evaluate the kinematics of deep knee flexion using 2–3-dimensional registration techniques. The mean knee flexion range of motion was 117.8°. The mean rotation of the femoral component was 7.6° external rotation. The mean knee flexion angle at initial post-cam engagement was 55.2°. No paradoxical movement of femoral component was shown until 70° flexion, afterward the femoral component rolled back with flexion. The data showed that the design of this prosthesis might contribute to reduce the paradoxical anterior femoral movement and provide stability in mid-flexion ranges.

Dismount of the Goat Tyer Athlete

There is a general understanding that the goat tying athlete has a moderate risk of injury to the ACL. Understanding why is important for improving prevention efforts. Studies that support the neuromuscular relationship to knee injuries in the female athlete refer to the angle of the knee and torso upon landing as a risk factor. PURPOSE: To examine the dismount knee and torso angles of the goat tyer athlete using 2-dimensional video analysis to discover what knee flexion angle and torso angle are common in the event. The relationship between the trunk and the knee angle was examined to evaluate the location of the center of gravity in relation to the knee upon impact. METHODS: Twenty-four female competitors (18–25y) in the goat-tying event at three intercollegiate rodeos participated in the study. Athletes were video taped from the side during live performance at one of the rodeos. Tape markers were placed at the knee joint and the greater trochanter to assist with analysis. Boot heel midline was used for distal landmark. All videos were clipped to the beginning of the dismount until just after toe-off of the second leg. Video analysis was used to measure the impact angle of the right and left leg and trunk angle in relation to the ground in the initial landing phase. Descriptive statistics and Pearson bi-variate correlation coefficients were used for analysis. RESULTS: There was no significance found between torso angle and right knee flexion on impact (r = −.130; p = .544). Mean right knee flexion angle at impact was 12.34° with a range of 23.34–3.58° knee flexion. Mean left knee flexion angle at impact was 20.25° with a range of 3.56–47.12°. All athletes impacted with the right knee within the 0-30° knee flexion angle range identified as higher risk for ACL injury. Only five athletes impacted with a left knee angle beyond the 0–30° knee flexion angle. Average trunk angle on impact was 20.70° with a range of 10.35–58.89°. CONCLUSIONS: The goat tying athlete performs the dismount from the horse near full right knee extension placing the knee at risk for ACL injury. Further research is indicated to help identify additional predictors for knee injury. PRACTICAL APPLICATIONS: Understanding that the goat tying athlete is at risk for knee injury, it is important to consider the mechanics of the sport from the anterior view as well as discovering additional factors such as speed on dismount which may increase the risk of injury in this sport.

Mechanisms for Noncontact Anterior Cruciate Ligament Injuries

Background The mechanism for noncontact anterior cruciate ligament injury is still a matter of controversy. Video analysis of injury tapes is the only method available to extract biomechanical information from actual anterior cruciate ligament injury cases. Purpose This article describes 3-dimensional knee joint kinematics in anterior cruciate ligament injury situations using a model-based image-matching technique. Study Design Case series; Level of evidence, 4. Methods Ten anterior cruciate ligament injury video sequences from women's handball and basketball were analyzed using the model-based image-matching method. Results The mean knee flexion angle among the 10 cases was 23° (range, 11°-30°) at initial contact (IC) and had increased by 24° (95% confidence interval [CI], 19°-29°) within the following 40 milliseconds. The mean valgus angle was neutral (range, -2° to 3°) at IC, but had increased by 12° (95% CI, 10°-13°) 40 milliseconds later. The knee was externally rotated 5° (range, -5° to 12°) at IC, but rotated internally by 8° (95% CI, 2°-14°) during the first 40 milliseconds, followed by external rotation of 17° (95% CI, 13°-22°). The mean peak vertical ground-reaction force was 3.2 times body weight (95% CI, 2.7-3.7), and occurred at 40 milliseconds after IC (range, 0-83). Conclusion Based on when the sudden changes in joint angular motion and the peak vertical ground-reaction force occurred, it is likely that the anterior cruciate ligament injury occurred approximately 40 milliseconds after IC. The kinematic patterns were surprisingly consistent among the 10 cases. All players had immediate valgus motion within 40 milliseconds after IC. Moreover, the tibia rotated internally during the first 40 milliseconds and then external rotation was observed, possibly after the anterior cruciate ligament had torn. These results suggest that valgus loading is a contributing factor in the anterior cruciate ligament injury mechanism and that internal tibial rotation is coupled with valgus motion. Prevention programs should focus on acquiring a good cutting and landing technique with knee flexion and without valgus loading of the knee.

Comparison of Knee Function After Antegrade and Retrograde Intramedullary Nailing for Diaphyseal Femoral Fractures: Results of Isokinetic Evaluation

To evaluate knee function in patients having femoral diaphyseal fractures treated with antegrade or retrograde intramedullary nail insertion. Prospective. Level I referral center. Seventy patients having 71 OTA 32 fractures were randomly allocated into 2 groups to be treated with either antegrade or retrograde intramedullary nails inserted with reaming. Antegrade nail in 41 fractures and retrograde femoral intramedullary nails in 30 fractures. Postoperative knee range of motion, Lysholm Knee Score, and isokinetic knee muscle function testing at least 6 months after documented fracture healing, minimum 1 year postoperatively. Groups had similar data with regard to demographics and injury patterns. Mean follow-up time was 44 (range: 25-80) months. Mean knee flexion angle was 132 and 134 degrees, and mean Lysholm Score was 84 and 83.1 in antegrade and retrograde groups, respectively (P = 0.893 and P = 0.701). Isokinetic evaluation revealed similar results for peak torque deficiencies at 30 and 180 degrees per second and total work deficiencies at 180 degrees per second (P > 0.05). Age affected the knee functioning as the higher the age of the patient is, the lower the Lysholm Score and knee flexion angle (r = -0.449, P = 0.0321 and r = -0.568, P = 0.001, respectively). Knee function seems to have similar clinical results after either antegrade or retrograde nail insertion for femoral diaphyseal fractures when knee range of motion, Lysholm Scores, and isokinetic knee evaluation are considered as outcome measures. With increasing patient age, a decrease in knee functioning should be anticipated in patients with femoral fractures treated with intramedullary nails regardless of technique.

Mechanisms of Anterior Cruciate Ligament Injury in Basketball

Background The mechanisms of anterior cruciate ligament injury in basketball are not well defined. Purpose To describe the mechanisms of anterior cruciate ligament injury in basketball based on videos of injury situations. Study Design Case series; Level of evidence, 4. Methods Six international experts performed visual inspection analyses of 39 videos (17 male and 22 female players) of anterior cruciate ligament injury situations from high school, college, and professional basketball games. Two predefined time points were analyzed: initial ground contact and 50 milliseconds later. The analysts were asked to assess the playing situation, player behavior, and joint kinematics. Results There was contact at the assumed time of injury in 11 of the 39 cases (5 male and 6 female players). Four of these cases were direct blows to the knee, all in men. Eleven of the 22 female cases were collisions, or the player was pushed by an opponent before the time of injury. The estimated time of injury, based on the group median, ranged from 17 to 50 milliseconds after initial ground contact. The mean knee flexion angle was higher in female than in male players, both at initial contact (15° vs 9°, P = .034) and at 50 milliseconds later (27° vs 19°, P = .042). Valgus knee collapse occurred more frequently in female players than in male players (relative risk, 5.3; P = .002). Conclusion Female players landed with significantly more knee and hip flexion and had a 5.3 times higher relative risk of sustaining a valgus collapse than did male players. Movement patterns were frequently perturbed by opponents. Clinical Relevance Preventive programs to enhance knee control should focus on avoiding valgus motion and include distractions resembling those seen in match situations.

Effectiveness of Serial Stretch Casting for Resistant or Recurrent Knee Flexion Contractures Following Hamstring Lengthening in Children With Cerebral Palsy

A retrospective review of all cerebral palsy (CP) patients with resistant or recurrent knee flexion contractures treated with serial stretch casting was performed. The protocol consisted of sequential wedging (5 degrees per week) of fiberglass casts until maximum knee extension had been achieved. Measurements were made prior to the initiation of casting, at completion of the casting, and at 1 year after the casting. Forty-six subjects, with 75 involved extremities, met the study inclusion criteria. Mean age at the time of initiation of casting was 12.7 years. Using radiographic measurements, the mean initial degree of knee flexion contracture was -17.6 degrees. At the completion of casting, the mean knee flexion angle was -8.1 degrees. The mean duration of casting was 30 days. At 1 year after completion of the casting, the mean knee flexion angle was -12.2 degrees. Initial correction to within 10 degrees of full extension was achieved in 76% of extremities. Age less than 12 years and initial flexion contracture of less than -15 degrees were statistically significant factors related to maintenance of correction at 1 year. Complications included soft tissue compromise in 13 extremities (17%), transient neurapraxia in 9 extremities (12%), and tibial subluxation in 1 extremity (1%). Serial stretch casting was successful in correcting resistant knee flexion contractures in the majority of cases. Casting was less effective in teenagers and those with larger contractures. Complications were minimized by proper casting technique and controlled rate of correction.

Gender Differences in Knee Angle on Landing from a Drop-Jump: Kinematic Data in Young Adults

There is a risk of injury to the knee during landing. The kinematics involved in different landing strategies may be related to the occurrence of trauma. Several sources suggest that the angle of knee extension on touchdown and impact with the ground determines the magnitude of the impact force and, indirectly, knee loading. This study compared the initial knee angle, maximum knee flexion angle, and angular velocity at the instant of impact on drop-landings between healthy men and women. In this study, 48 participants (25 male, 23 female) dropped from a height of 40 cm onto their right leg. The CMS-HS measuring system was used to analyze the kinematic data. There was no significant difference in the mean knee flexion angle at landing between the two groups. However, the range of knee flexion on landing (43.64 ± 4.63° in men, 37.40 ± 6.23 ° in women) and the angular velocity (0.25 ± 0.04 °/sec for men, 0.23 ± 0.04°/sec for women) differed significantly (p<0.05). Women land with a straighter knee than men and this might increase the likelihood of a knee injury.