• Pre autologous donation (PAD), where the patient donates his or her own blood for four weeks prior to surgery. This blood is then tested and stored for autologous use should it be required. However this method requires several trips to the hospital prior to the surgery, and is reliant on guaran- teed bed availability. The National Blood Service, due to the logistical issues involved, no longer recommends PAD.
• Intra operative salvage, where a machine collects blood shed during the operation. The shed blood is processed and reinfused, usually during the operation. This method is only useful and cost effective where there is high intra operative blood loss (>1000ml).
• Postoperative salvage where unwashed shed blood is collected after the operation, is filtered and then transfused back to the patient. This method is most commonly used on Total Knee Replacements and Total Hip Replacements. Generally a tourniquet is used during knee replacement surgery and therefore blood loss tends to be greatest in recovery or post operatively. The effectiveness of this technique is well documented^{4, 5, 6}.

• Compare data on 20 patients receiving CellTrans™ postoperative salvage system to 20 patients who did not receive any alternatives to donor blood.
• Collect data on Pre and Postoperative FBC (Hb) and Clotting (PT and APTT) results (in both groups).
• Collect data on volume of donor blood given (in both groups).
• Collect data on the volume of salvaged blood re-infused (CellTrans™ group only).
• Analyse the data to establish whether the use of CellTrans™ has reduced the usage of donor blood for this surgical procedure.
• Analyse the data to ensure that similar pre and post operative Hb and clotting results are obtained in the two groups.

Donor blood group (Group 1)
19 patients underwent routine Knee Replacement surgery without the postoperative collection system. Almost all the data (18) was collected from patients who underwent the procedure prior to CellTrans™ being available, 1 patient declined treatment via CellTrans™.

CellTrans ™ group (Group 2)
22 CellTrans Postoperative Autologous sets were made available for patients having a Total Knee Replacement. Patients were given a patient information leaflet, and consented on a surgical consent form to autologous postoperative collection. 21 patients agreed to receive donor blood in addition to autologous should the need arise. The data collected was: volume of blood recovered and reinfused; pre and post operative Hb levels, pre and post operative coagulation results and the volume of donor blood required.

• There was no significant difference between the pre haemoglobin results in Group 1 compared to Group 2.
• No significant difference in pre and postoperative PT and APTT results was observed between the groups. However there was insufficient data for a proper comparison.
• Although the sample size is small there is a significant reduction in the need to transfuse patients with donor units (58% to 9%).
• There was no significant difference in postoperative haemoglobin within the two groups and the mean fall in haemoglobin pre to post-operatively was 3g/dl in the CellTrans™ group and 2.7g/dl in the donor blood group.

Mr. Cheah’s paper showed no complications have been experienced by any of the patients and that the nursing staff had reported no difficulties in using the device. As a direct result of using the CellTrans™ device, cross-matching of patients is no longer required, thus saving further time, money and resource. None of the patients required homologous blood and the study showed a saving of £8,227 or 100 units of red blood cells. Mr. Cheah also noted that patients who had received their own blood were being discharged from hospital early.

At the Plymouth Nuffield, data on the use of CellTrans™ has been collected since November 2001, where the product is used routinely on TKR’s, uni-compartmental knees, knee revisions and Total Hip Replacements. A summary of their audit data at 207 patients showed that 79.2% of them had been reinfused with their own blood and only 17 (8.2%) needed to receive bank blood either peri- or post-operatively. Prior to using the device, all patients were routinely grouped and saved and had a 2 unit cross-match performed. Now, patients are only routinely grouped and saved, thus there is an immediate cost saving.

Wherever possible, it therefore seems appropriate for hospitals to use intra- and postoperative autologous cell salvage devices, which not only save this scarce resource for other procedures, but which have also shown to offer patient benefits. As Sue Hammond, sister at Morriston Hospital states, “our patients always seem reassured to know that they are getting their own blood back and this seems to play a part in their recovery.”

1. Serious Hazards of Transfusion Annual Report 2003.
2. A National Blood Conservation Strategy for the NBS: Report from Autologous Transfusion Working Party. V. Jones. Jan 2004.
3. Better Blood Transfusion II – Appropriate Use of Blood. HSC 2002/009
4. Transfusion 2002; 42, p66-75:
5. J Bone Joint Surg 1997; 79b,p630-632
6. Transfusion 1992, 32, p742-746

Since then several authors have published early and medium term results of unicompartmental knee replacement using minimally invasive surgery technique^1,2,3. In total hip arthroplasty using a minimally invasive technique, the damage to the underlying abductor and external rotator muscles is very small. This allows for reduced blood loss and reduced amount of pain, which in turn leads to quicker functional recovery. Now total knee arthroplasty is the latest procedure to come under the spotlight.

Standard total knee replacements can take up to 18 months for full functional recovery and at one year some studies have reported that only 35% of those with “good” results according to knee society scores had no limitation of activities⁴. Post-operative stiffness still remains a problem after standard total knee replacements. It has been reported that post-operative stiffness and extensor mechanism problems are the main cause of early revisions after total knee arthroplasty⁵. Further studies have reported that those patients with more post-operative pain required more physical therapy and a higher rate of manipulation^6,7.

There is also minimal or no invasion of the supra-patellar pouch, which decreases scarring and which can, over time, increase the range of motion in the knee. These benefits can result in more rapid recovery, leading to a reduction in the length of stay and potentially the risk of hospital-acquired infection. Earlier return to function also potentially reduces the rate of deep vein thrombosis and pulmonary embolism during the post-operative recovery period.

Severe contractures, if forced, can cause ligament avulsions and malrotation of the prosthesis. Those knees with patella baja for any reason are also not suitable for minimally invasive total knee replacement due to limited retraction possible and the risk of rupture of the patellar tendon. Patients with osteoporosis are also not suitable due to the risk of tibial tuberosity avulsion or patellar pole avulsion. Finally extreme deformity of the knee, more than 25 degrees valgus or varus deformities, can cause similar problems.

The tibial blocks need to “go around the corner” to avoid damage to the patellar tendon. The tibial templates fit around the patellar tendon, using special deep curved retractors for good exposure (Fig 4).

The skin incision is medial para-patellar from the proximal margin of the patella to the tibial tuberosity and usually measures about 10 centimetres in length. In difficult cases, it is possible to extend the incision into vastus medialis by about 2 centimetres: a “mini” mid-vastus approach.

A transverse incision into the medial capsule just distal to vastus medialis also helps in difficult cases. Sub-cutaneous dissection helps in moving the skin without putting excessive tension on the skin edges. The patella is subluxed and not everted. The lateral part of the joint is cleared to visualise the whole of the lateral compartment of the knee. The distal femoral cutting block is referenced from the medial femoral condyle.

As previously mentioned, reducing the size of the cutting instruments is the only way to perform the required femoral and tibial resections. Here the Microplasty™ instruments are compared with their standard alternatives (Fig 5).

The cutting blocks employ “sliding” technology to assist the cuts and allow full access to the bony surfaces (Fig 6 & 7).

The tibia is referenced off the medial tibial condyle and the cutting block is placed against the medial tibial condyle (Fig 8). This allows for cutting the entire tibial condyle. An offset tibial sizing template sits around the patellar tendon and allows for the use of tibial punches (Fig 9).

To obtain reliable results, there are certain requirements during surgery. Complete resection of the patellar fat pad is essential for good exposure of the lateral compartment. The patellar tendon has to be protected at all times. Soft tissue should be released all the way to the postero-medial corner. The postero-lateral corner needs to be protected during resection of both the femur and tibia and this requires deep curved retractors. When using a minimally invasive approach, there is a risk to both the skin and patellar tendon.

The surgeon needs to focus on component position and size as the approach may present additional problems such as cutting the tibia in valgus, downsize the tibia, insert the femoral component in internal rotation and medial placement. As a result of the additional care required, a minimally invasive approach does take longer than a standard approach

We have compared 25 cases where age, sex and BMI were matched using a minimally invasive technique against a standard open technique. The following parameters were measured: alignment of knee, percentage of tibial cover, percentage of femoral cover and extent of posterior tibial slope. There was no significant difference in any of these measured parameters. However, there was significant decrease in drop in post-operative haemoglobin with minimally invasive surgery. There was no difference in the length of stay.

At three months the range of movements was better with the minimally invasive approach group. This compares well with contemporary early results of other groups

With the recent increasing interest in using computer-assisted navigation for total knee replacement, combining navigation with a minimally invasive approach may represent a useful tool for assuring accurate component alignment. This does of course add yet another technical step into the operative equation. If these points are borne in mind minimally invasive total knee replacement will provide excellent short term results which can be transposed into long term results I recommend the minimally invasive surgical technique for total knee arthroplasty for experienced surgeons only.

The Microplasty™ Knee Instrumentation is available from Biomet Europe for the AGC®, Maxim™ and Vanguard™ knee systems.

Previous studies have also shown that female recreational athletes have lower extremity motor controls that may increase the load on their ACLs in specific athletic tasks, in comparison with their male counterparts.^7,21 For our long-term studies on the prevention of non-contact ACL injuries, we therefore hypothesized that women tend to have altered lower extremity motor controls that, in specific athletic tasks, frequently bring them close to positions in which non-contact ACL injuries may occur, thereby increasing their risk for non-contact ACL injuries.

One of the characteristics of female recreational athletes’ movement is their small knee flexion angle in landing tasks that are preceded with horizontal movements, such as stop-jump tasks.^7,21 Regarding biomechanics, decreasing the knee flexion angle at landing increases the loading on the ACL^{5,13,23,28,31} and thereby increases the risk for ACL injuries. As a natural continuation of our preliminary studies, the purpose of this study was to address the effects of constraining knee extension on lower extremity kinematics and kinetics by having recreational athletes wear a specially designed knee brace during a stop-jump task. It was hypothesized for this study that the specially designed knee brace would significantly increase the knee flexion angle at the landing of the stop-jump task and that the maximum ground reaction forces would be reduced as the knee flexion angle at landing increased.

Table 1 Subject Mean Age, Height, and Weight
Gender	Age, y	Body Weight, kg	Standing Height, m
Male	26.0 ± 2.5	83.5 ± 11.9	1.82 ± 0.1
Female	26.0 ± 2.6	61.9 ± 9.1	1.66 ± 0.1

Figure 1. The specially designed knee brace with a constraint to knee extension.

The newly designed knee brace with a constraint to knee extension was constructed using an existing functional knee brace (4titude; dj Orthopedics, LLC, Vista, Calif). The brace frame was made of 6061-T6 aluminum with upright upper thigh and lower calf cuffs. Hook-and-loop straps are used to attach the brace to the leg (Figure 1). The medium-size brace weighs 20 oz. The new design uses a spring mechanism to constrain knee extension. The resistance mechanism in the hinge (Figure 1) engages at 40° of knee flexion and applies a gradually increasing resistance to knee extension motion up to 10° of knee flexion, at which point a rigid stop prevents further knee extension. The resistive torque is adjustable with a maximum of 3 N•m at 10° of knee flexion. A total of 8 such braces were made for right and left sides in each of the 4 sizes: small, medium, large, and extra large.

The athletic task tested in this study was a vertical stop-jump task frequently performed in basketball and volleyball games. This task consists of an approach run, with up to 5 steps, and a 2-footed landing followed by a 2-footed takeoff for the maximum height (Figure 2). A recent review of more than 100 ACL injury cases on videotape³ revealed that 70% of non-contact ACL injuries occurred in stop-jump–related tasks. All subjects underwent testing in the Motion Analysis Laboratory of the Center for Human Movement Science of the University of North Carolina at Chapel Hill. Subjects signed informed consent forms before data collection. Subjects were instructed to have a 10-minute warm-up before data collection. The stop-jump task and the knee braces were described to the subject; demonstration of the task was avoided to minimize coaching effects. All subjects were blinded to the hypothesis of this study.

Figure 2. The stop-jump task

Passive reflective markers were placed on each subject bilaterally at the anterior superior iliac spine, lateral malleolus, upper anterior aspect of the tibia, and lower anterior aspect of the tibia. A marker was also placed on the lower spine at the L4-L5 joint.¹⁷ The subjects performed the stop-jump task with the above-described markers. Each subject performed 5 successful trials of the stop-jump task at the maximum approach run speed and vertical jump effort he/she felt comfortable with for each of the 2 brace conditions: (1) without brace and (2) with the specially designed knee brace with a constraint to knee extension. The order of the 2 conditions was randomized. The newly designed knee brace, in the appropriate size, was applied to the dominant leg of each subject. The dominant leg was defined as the leg the subject used for single-leg jumping.

Three-dimensional (3D) videographic and force plate data were collected for each subject in the stop-jump task for the 2 brace conditions. Six infrared video cameras were used to collect the trajectories of reflective markers on the subject at a frame rate of 120 frames/s. The 6 infrared cameras were calibrated for a 2.5 m long x 1.5 m wide x 2.5 m high space (calibration volume), in which the subject performed the stop-jump task. Two Type 4060A Bertec force plates (Bertec Corp,Worthington, Ohio) were used to collect the ground reaction force signals at a sample rate of 1200 samples/channel/s. The videographic and ground reaction force signals were recorded by the Peak Performance Motus videographic and analog data acquisition system (Peak Performance Technology Inc, Englewood, Colo). The videographic and force plate data collection was time synchronized to 1200 frames/s and 1200 samples/channel/s.

Additional 3-D videographic data were collected in a standing trial after all the stop-jump trials. Additional passive reflective markers were placed bilaterally at the medial malleolus and medial and lateral femur condyles. These additional markers were used to estimate the locations of those critical body landmarks that were needed for calculating joint centers but that were not clearly visible when the subjects were performing the stop-jump task. Each subject was asked to stand in the middle of the calibration volume. The 3-D videographic data of all reflective markers were collected.

The collected 3-D coordinates of the markers during each stop-jump trial were filtered through a Butterworth lower-pass digital filter at estimated optimum cutoff frequencies.³³ The 3-D local coordinates of the medial and lateral femur condyles and medial malleolus were estimated from the 3-D coordinates of markers on the tibia in the standing trial. The 3-D coordinates of the hip joint centers in stop-jump trials were estimated from the 3-D coordinates of the reflective markers on the right and left anterior superior iliac spines and L4-L5 joints and on anatomical data.3 The 3-D coordinates of the medial and lateral femur condyles and medial malleolus in stop-jump trials were estimated from the local coordinates of the corresponding markers in the standing trials, and the direction cosine matrices of the tibia was defined by the 3-D coordinates of the markers on the tibia in stop-jump trials. The knee joint center was defined as the middle point between the medial and lateral femur condyles. The ankle joint center was defined as the middle point between the medial and lateral malleolus. The 3-D coordinates of the knee and ankle joint centers and medial and lateral malleolus were used to define the tibia reference frame. The 3-D coordinates of the knee and hip joint centers and medial and lateral femur condyles were used to define the femur reference frame. The knee joint angles were determined as Euler angles of the tibia reference frame relative to the femur reference frame rotated in order of (1) flexion-extension (z-axis), (2) varus-valgus (y-axis), and (3) internal-external rotation (x-axis).4 The electric signals from the force plates were converted to forces. All signal processing and data reduction were performed using a MotionSoft 3-D motion data reduction program package version 5.5 (MotionSoft Inc, Chapel Hill, NC). The validity and reliability of estimated joint centers and angles can be found in other studies.^3,6,17,18,34

The stance phase of the stop-jump task was defined as the duration from the time of landing to the time of takeoff. The time of landing was defined as the time represented by the first frame in which the vertical ground reaction force was greater than zero after the approach run. The time of takeoff was defined as the time represented by the first frame in which the vertical ground reaction force was zero after the landing. The entire stance phase of the stop-jump task was divided into 2 phases: landing and jumping phases. The landing phase was defined as the duration from the time of landing to the time of the maximum knee flexion angle. The jumping phase was defined as the time of the maximum knee flexion angle to the time of takeoff. The approach run speed, knee flexion angle at the landing, maximum knee flexion angle, range of knee flexion motion, and maximum posterior, medial, and vertical ground reaction forces during the landing phase were identified for each trial. The approach run speed was defined as the magnitude of the mean horizontal velocity of the hip joint centers at the time of landing. The range of the knee flexion motion during the landing phase was defined as the difference between the maximum knee flexion angle during the stance phase of the stop-jump task and the knee flexion angle at the landing. The data from the first 3 successful trials in each condition were used for data analysis.

Analyses of variation with mixed design were conducted to compare the knee flexion angle at the landing, maximum knee flexion angle, and range of knee flexion motion with maximum posterior, medial, and vertical ground reaction forces during the landing phase of the stop-jump task. The brace condition was treated as a repeated measure, whereas gender was considered an independent measure. In case of a significant brace condition by gender interaction effect on a given dependent variable, analyses of variance were conducted to compare the dependent variable between brace conditions as a repeated measure for each gender and between genders as independent groups for each brace condition. A type I error rate of .05 was chosen to indicate statistical significance in each analysis. All statistical analyses were performed using the SYSTAT computer program package, version 5.0 (SYSTAT Inc, Evanston, Ill).

Figure 3. Approach run speed of the stop-jump task with and without the new knee brace. Male subjects had significantly greater approach run speed than did female subjects in both brace and non-brace conditions (P = .000).	Figure 4. Jump height of the stop-jump task with and without the new knee brace. Male subjects jumped significantly higher than did female subjects (P = .000).
Figure 5. Knee flexion angle at the landing of the stop-jump task with and without the new knee brace. Both male and female subjects had significantly greater knee flexion angles at landing with the brace than without the brace (P = .001). Male subjects had significantly greater knee flexion angles than did female subjects in both brace and nonbrace condi-tions (P = .003).	Figure 6. Maximum knee flexion angle during the landing of the stop-jump task with and without the new knee brace. Male subjects had significantly greater maximum knee flexion angles than did female subjects in both brace and non-brace conditions (P = .001).

The specially designed knee brace significantly increased knee flexion angle at the landing in the stop-jump task on average from 27.4° to 32.5° for male subjects and from 22.3° to 27.6° for female subjects (P = .001) (Figure 5). Female subjects had significantly smaller knee flexion angles at the landing in the stop-jump task than did male subjects in both brace and nonbrace conditions (P = .003) (Figure 5).

There was no significant effect on the maximum knee flexion angle in the stop-jump task (P = .508) in the knee brace condition (Figure 6). Female subjects had significantly smaller maximum knee flexion angles in the stop-jump task than did male subjects in both brace and nonbrace conditions (P = .001) (Figure 6).

The specially designed knee brace significantly reduced the angle of the range of knee flexion motion in the stop-jump task on average from 49.4° to 41.3° for male subjects and from 46.3° to 41.9° for female subjects (P = .015) (Figure 7). There was no significant difference in the range of knee flexion motion in the stop-jump task between male and female subjects (P = .498) (Figure 7).

There was no significant effect on the maximum posterior ground reaction force in the stop-jump task from the knee breace (P = .588) (Figure 8). Female subjects had significantly greater posterior ground reaction force in the stop-jump task than did male subjects in both brace and nonbrace conditions (P = .007) (Figure 8).

Figure 7. Range of knee flexion motion during the landing of the stop-jump task with and without the new knee brace. Both male and female subjects had significantly smaller ranges of knee flexion motion with the brace than without the brace (P = .015).	Figure 8. Peak posterior ground reaction force during thelanding of the stop-jump task with and without the new knee brace. Female subjects had significantly greater maximum posterior ground reaction force during the landing phase than did male subjects in both brace and nonbrace conditions (P = .007). The peak posterior ground reaction force was normalized to body weight (BW).
Figure 9. Peak medial ground reaction force during the land-ing of the stop-jump task with and without the new knee brace. Female subjects had significantly greater maximum medial ground reaction force during the landing phase than did male subjects in both brace and nonbrace conditions(P = .000). The peak medial ground reaction force was nor-malized to body weight (BW).	Figure 10. Peak vertical ground reaction force during the landing of the stop-jump task with and without the new knee brace. Female subjects had significantly greater vertical ground reaction force than did male subjects in both brace and nonbrace conditions (P = .003). The peak vertical ground reaction force was normalized to body weight (BW).

There was no significant effect on the maximum medial ground reaction force in the stop-jump task (P = .708) in the knee brace condition (Figure 9). Female subjects had significantly greater medial ground reaction forces in the stop-jump task than did male subjects in both brace and non-brace conditions (P = .000) (Figure 9).

There was no significant effect on the maximum vertical ground reaction force in the stop-jump task (P = .708) in the knee brace condition (Figure 10). Female subjects had significantly greater vertical ground reaction forces in the stop-jump task than did male subjects in both brace and nonbrace conditions (P = .003) (Figure 10).

The desired function of the mechanism to constrain knee extension while wearing the specially designed knee brace was to modify lower extremity kinematics and kinetics and to reduce the load on the ACL in athletic tasks by increasing the knee flexion angle at the landing. The results of this study supported our hypothesis that the knee brace would significantly increase the knee flexion angle at the landing in the stop-jump task, but they did not support our hypothesis that the knee brace would significantly reduce the maximum ground reaction forces in the stop-jump task. The significant increase in the knee flexion angle at the landing with the specially designed brace was not likely the effect of approach run speed because there was no significant difference in the approach speeds between the brace and nonbrace conditions.

The results of this study also suggested that the specially designed knee brace did not significantly affect the maximum knee flexion angle in the stop-jump task. The significant decrease in the range of knee flexion motion in the stop-jump task with the knee brace was mainly due to the increase in the knee flexion angle at the landing in the knee brace condition. It is likely that the specially designed knee brace did not significantly affect the knee joint resultant forces and moments in this study. These forces and moments are mainly determined by the ground reaction forces and moments because of the relatively small masses and moment of inertia of the foot and shank. There are not likely to be significant differences in knee joint resultant forces and moments if there are no significant differences in ground reaction forces. These results combined together indicated that the specially designed knee brace significantly increased the knee flexion angle at the landing in the stop-jump task, as it was designed to do, but it did not significantly modify other lower extremity kinematics and kinetics in the stop-jump task as it was expected to. q Although the specially designed brace did not significantly reduce the maximum ground reaction forces, it should still have served the overall purpose of the design— to reduce the load on the ACL—because increased knee flexion angle at the landing should assist in reducing the anterior shear force applied on the tibia through the patellar tendon. Studies repeatedly have shown that the anterior shear force applied on the tibia through the patellar tendon is a function of the knee flexion angle.^{4,13,23,28,31} The anterior shear force applied on the tibia through the patellar tendon decreases as the patellar tendon–tibia shaft angle decreases, whereas the patellar tendon–tibia shaft angle decreases as the knee flexion angle increases. Therefore, anterior shear force applied on the tibia through the patellar tendon decreases as the knee flexion angle increases. According to the results of a recent study by Nunley et al,²⁷ the patellar tendon–tibia shaft angle, on average, will be decreased from 19.0° to 17.4° for women and from 13.8° to 12.3° for men when their knee flexion angles increase from 22.3° to 27.6° and from 27.4° to 32.5°, respectively. This means that the anterior shear force applied on the tibia through the patellar tendon, on average, will be reduced by 9% for women and by 13% for men if they increase their knee flexion angles from 22.3° to 27.6° and from 27.4° to 32.5°, respectively. The decrease in the anterior shear force on the tibia should significantly reduce the load on the ACL if other conditions remain the same.

The results of this study indicate that increased knee flexion angle at the landing does not necessarily mean a soft landing. A study by DeVita and Skelly ⁹ showed that subjects had increased knee flexion angles at the landing and decreased maximum vertical ground reaction forces in a drop landing task when using the soft landing technique in comparison with the knee flexion angles and vertical ground forces when using the hard landing technique. An increase in the knee flexion angle at the landing was recommended to reduce the maximum vertical ground reaction force in the landing. The results of our study, however, indicated that increased knee flexion angle was not likely the cause of the decreased maximum ground reaction force in the study by DeVita and Skelly ⁹ and, therefore, may not be a critical kinematic characteristic of a soft landing.

The results of this study are in agreement with the literature. Malinzak et al²¹ and Chappell et al⁷ reported that female recreational athletes had decreased knee flexion angles at the landings of running, cutting, drop landing, and stop-jump tasks in comparison with their male counterparts. The results of the present study showed that female subjects had a smaller knee flexion angle at landing than did male subjects at the landing in the stop-jump task. Chappell et al⁷ reported that female recreational athletes showed increased maximum anterior shear force at the proximal tibia at the landing in 3 stop-jump tasks in comparison with their male counterparts. The posterior ground reaction force is a major contributor to the anterior shear force at the proximal tibia. The results of the present study showed that female subjects, on average, had increased posterior ground reaction force at the landing in the stop-jump task. Chappell et al⁷ reported that female recreational athletes on average had a valgus moment at the knee, whereas male recreational athletes on average had a varus moment at the knee at the landings of 3 stop-jump tasks. A medial ground reaction force and a valgus knee are contributors to the knee valgus moment. The results of the present study showed that female subjects had increased medial ground reaction force compared with that of male subjects at the landing in the stop-jump task, whereas Malinzak et al²¹ reported that female recreational athletes on average had valgus knee and male recreational athletes on average had slightly varus knee at the landings of selected athletic tasks.

Further studies are needed to fully understand the effects of the specially designed knee brace with constraint to knee extension on the lower extremity kinematics and kinetics in athletic tasks and potential clinical applications. Although in the present study the subjects increased their knee flexion angles at the landing of the stop-jump tasks, it is not clear if the increased knee flexion angles were due to the effect of constraining the knee extension or the effect of knee bracing. We did not find evidence in our extensive literature review showing that knee braces without constraint to knee extension assist in reducing knee flexion angle at landings in athletic tasks. Further studies are needed to determine the effects of constraining the knee extension and of purely knee bracing on the lower extremity kinematics and kinetics in athletic tasks. Also, the results of the present study only showed the immediate effects of the specially designed brace on the knee kinematics and kinetics in the stop-jump task. Further studies are needed to determine the long-term training effects of wearing the specially designed knee brace on the lower extremity kinematics and kinetics as compared with not wearing the brace. The present study only investigated the effects of the specially designed knee brace on ground reaction forces. Although the results of the present study showed that wearing the specially designed knee brace did not significantly affect the performance and ground reaction forces in the stop-jump task, and may not affect knee joint resultant moments in the stop-jump task, it is still possible that wearing a knee brace may affect the muscle contraction patterns and techniques to perform athletic tasks. Further studies are needed to compare knee muscle contraction patterns in the stop-jump task with and without the specially designed knee brace. The results of the present study showed a potential to apply the specially designed knee brace in the rehabilitation of ACL injury patients. The present study, however, only tested the immediate effects of the specially designed brace on the knee kinematics and kinetics of healthy recreational athletes without knee injuries. Further studies are needed to determine the effects of the specially designed knee brace on the lower extremity kinematics and kinetics of patients with ACL injuries in post-injury rehabilitation programs.

The results of this study appear to warrant the following conclusions:

1. The immediate application of the specially designed knee brace with the constraint to the knee extension significantly increased knee flex- ion angle at the landing in the stop-jump task by a mean of 5° for both male and female recreational athletes.
2. The specially designed knee brace with the constraint to the knee extension did not significantly affect the maximum ground reaction forces during the landing phase of the stop-jump task, and the immedi- ate application of the knee brace may not affect the knee joint resultant forces and moments of recreational athletes.
3. The increased knee flexion angle at the landing of the stop-jump task with the specially designed knee brace may assist in reducing the load on the ACL during the landing in the stop-jump task as well as in other athletic tasks, at least in the immediate application of the knee brace.
4. Further studies are needed to fully understand the potential functions of the specially designed knee brace with the constraint to knee extension in the prevention and rehabilitation programs for ACL injuries.

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Once my measurements were taken for the brace, I chose a nice metallic red colour from a seemingly endless range of colours and expected to receive the finished articles in the coming weeks, what with them having to be custom manufactured over in the US.

So, seeing as I was fitted on the Thursday at the BOA, you can imagine my surprise when they turned up the following Monday morning! If this is indicative of their standard customer care, then it is very impressive.

To see if the product matched the service, I promised to review them for the magazine, so last month I somehow forced myself to head off to Chamonix, France for a spot of weekend skiing - the things an editor has to do to please his readers - they are meant for that sort of thing, you know. I originally thought of doing this test, not because I have any ACL problem, but because as I race towards forty I thought prevention is better than cure!

Originally, the plan was to test the braces on both knees for three days, but someone in our party had a painful knee after day one - a really decent guy called Trevor Smith, who had not been on the slopes for a while and I think may have pushed himself too far - nothing to do with me.

Now, Trevor is exactly how you would want to be if you were in your sixties - an international man of mystery, Trevor looks forty-five, is very successful and is in great physical shape, with a sharp wit to go with it. Even more irritatingly, he is unreasonably popular with the opposite sex, plus he is a nice guy too, but I digress!

When Trevor asked me if he could borrow a brace I could hardly refuse, and it actually turned out well. By the end of day two Trevor still had a painful knee, but this time it was the non-braced one, the other one had been fine. Trevor declared the brace a success, saying that without it he would not have been able to ski all day - he now considered himself a convert and told me he was going to invest in a pair.

“I played professional rugby for Bradford for years and have had a previous knee injury. I would not have been able to ski at all on day two if I had not used the brace. I would recommend anyone doing anything physical to have one - I certainly wish I had used it on the first day.”

As for my experience with the other brace, once it was fitted it took about five minutes to forget that you actually had it on. It was lightweight and the straps are perfectly placed to cause minimal agitation. I needed to adjust a few of them after the first few minutes use to get the right fitting, but after that I left them alone. I found it incredibly comfortable for the first six hours of constant use, by then the straps were wet from falling and exertion and they began to get a little sore, but then again, would the average user wear them for eight hours solid?

A few times after falling I felt the brace stop my knee hyper-extending -this basically allowed me to be incredibly aggressive on the slopes without having to worry too much about the consequences; I can’t believe it has taken this long to work it out.

Apart from the obvious benefit of avoiding an ACL injury, I came across a few more. Firstly, the brace provides a lot of support for the knee generally - like Trevor, my knees always get slightly sore skiing, but not the one with the brace on. Another benefit was that if you took a tumble the brace made contact with the ground first and disperses the load over a wide area of the leg, so no bruises or injuries from rocks or ice. I would say it is worth wearing a brace for this benefit alone.

Our ski party of over twenty adults (I was the youngest there, naturally) all asked relevant questions and seemed curious. Given more time - or sales commission - I would have let them have a go as I think a good few would have bought them after trying them just as a preventative measure.

My only minor gripe is that the instructions provided were not up to the job. However, an inexperienced end user would not normally receive a box and be allowed to fit the braces for themselves without any supervision, so this is not a reflection on the service dj Ortho provide.

A special thanks must go to them for allowing me the opportunity to test their products. I was really impressed by the product and will now always wear a knee brace whilst performing any kind of contact sport. I wonder if the sales team at dj get to try their braces in anger? If they don’t, then they should, as I’m sure they would be impressed too.