CHAPTER DISCUSSIONS ~ It is more noble by silence to avoid an injury than by argument to overcome it. ~ Francis Beaumont 147 6. DISCUSSIONS 6.1 Understanding Biomechanics of Landing In view of previous landing studies, the relationships of landing height with GRF, knee flexion angles, angular velocities and joint powers are not well understood and there is an existing limitation in obtaining these data at very large landing height in a controlled laboratory setting. The regression work in Stage A aimed to investigate these relationships through a series of landing tasks from a range of landing heights (0.15-1.05m) which were commonly tested; these relationships may be employed to predict these parameters at large landing heights. The range of peak GRF obtained in this stage was slightly lower compared to previous studies (Mizrahi and Susak, 1982; Dufek and Bates, 1990; McNair and Marshall, 1994; McNitt-Gray, 1993; Seegmiller and McCaw, 2003; Kernozek et al., 2005; Pappas et al., 2007), though the peak GRF data obtained among all these studies were quite varied. This may be explained by the type of landing style adopted by the different subjects in these studies. DeVita and Skelly (1992) stated that a soft landing style produces a mitigated GRF compared to stiff landing. Moreover, it was previously reported that gymnasts who tend to land with minimal knee flexion incurred higher GRF than recreational athletes (Seegmiller and McCaw, 2003). In this study, it was notable to observe a marked exponential relationship between peak resultant GRF and landing height. The presence of larger peak impact force indicated weaker shock-absorbing capacity, which may increase the susceptibility to lower-extremity overuse injuries (Bus, 2003; Hargrave et al., 2003). The results established that the peak GRF incurred during landing is highly dependent on landing height and the exponentially-elevated 148 peak GRF during landing from a great height can potentially heighten the risk of developing lower extremity injuries. The knee flexion angles at initial contact and at peak GRF demonstrated inverse-exponential relationship with landing height. The gradual increase in knee flexion angles at both events with landing height up to 0.75m may represent the inherent mechanism of the musculoskeletal system to increase knee flexion so as to provide enhanced shock absorption capacity against the elevated GRF (Hargrave et al., 2003; Coventry et al., 2006). However, at landing heights beyond 0.75m, the knee flexion angles at initial contact and at peak GRF were found to increase at a slower rate. The reduced rate of increase observed in these knee flexion angles may contribute to diminished shock absorption in response to exponentially increasing peak GRF. DeVita and Skelly (1992) reported that a soft landing style leads to an attenuated GRF relative to stiff landing. Thus, the presence of lower knee flexion during stiff landing can lead to a diminished shock absorption capacity, whereby the articular cartilage will sustain large compressive impact loads that can afflict cartilage lesions (Lafortune et al., 1996; Hargrave et al., 2003). Yu et al. (2006) previously demonstrated that the knee flexion angular velocity has a negative correlation with peak GRF during landing, which implied that active knee flexion, in the form of higher rate of increase in knee flexion with time, is an important player in impact force attenuation. Furthermore, the presence of a negative knee joint power revealed eccentric work done on knee extensors to dissipate impact energy. Zhang et al. (2000) reported that negative knee joint power increased with landing height, which suggested that the knee extensors were vital contributors to energy dissipation. Additionally, in the current study, an inverse-exponential relationship was noted 149 between knee flexion angular velocity and landing height, and a simple linear relationship between knee joint power and landing height. Altogether, these findings suggested that the energy dissipation capacity of the knee joint increased at a relatively slower rate at higher landing heights despite the exponentially-increasing GRF parameters. This ‘misbalance’ between energy dissipation capacity and GRF parameters at great landing heights is likely to aggravate lower extremity injury risk. One key limitation of this study is the progressive conduct of the landing tasks with regards to the landing height. Potential injury risks may exist in randomized landing trials; for instance, if the subjects were to perform the landing trials with greater height (0.90-1.05 m) initially, there is a higher tendency for injury compared to having the landing trials with lower height (0.15-0.30 m) conducted first. Though the findings of this study may not be completely reflective of the actual landing condition wherein an athlete lands from a large height in a single task, this progressive landing protocol was beneficial as it helps the subjects to attune to the landing style that best facilitates them in shock attenuation. Another limitation is perhaps the potential inter-subject differences in landing style, which may influence the regression relationships obtained for each subject between the dependent and independent variables. Although the subjects were not specificially instructed to follow a standardized landing style, a qualitative examination of their landing motions revealed mostly ‘soft’ landing styles which may explain the lower peak GRF obtained compared to previous studies. Since the current study was more concerned with investigating the effect of landing height on GRF, knee flexion angles, angular velocities and joint powers for recreational athletes who have different landing experiences, the subjects were permitted to execute their natural landing styles. Setting a standardized landing style for all subjects may 150 introduce confounding variables such as the individual ability in learning the landing style; a standardized landing style would be more relevant for studies on specific groups of athletes, such as gymnasts and volleyball players, who would possess similar levels of learning ability and landing experience. It is important to note that the study was constrained by a small sample size, hence the results may not be representative of the general population. However, the post-hoc power analysis revealed that there was generally a sufficiently high power to detect the observed regression relationships in the data obtained in this study. While it cannot be concluded the general population would follow these regression relationships during landing, the study was able to show that the relationships have a strong fit in terms of R2 and p values for the subjects tested in this regression study. In addition, there are certain factors in a physiological landing task specific to a sports-/military-related setting, like upper body motion, friction/gradient of landing surface, type of shoe/boots worn, additional carried weights and post-landing maneuvers, which are not examined in the current study. These factors may usually cause unexpected effects on the landing biomechanics of the athlete and elevate injury risk (Dufek and Bates, 1991). Since the intention of this study was to investigate the regression relationships of landing height with GRF, knee flexion angles, angular velocities and joint powers, it is therefore necessary to conduct the present study in a controlled laboratory environment so that the subjects knew exactly what to expect and can perform the same sets of landing tasks with minimal injury risk. We further acknowledged that one limitation of this study was, perhaps, the usage of male subjects. This project was performed in collaboration with the Defence Medical and Environmental Research Institute, which necessitated the testing of male subjects as the local males (at the age of 18) are subjected to military conscription and 151 form a dominant population of our armed forces. Hence, there is a need to identify the biomechanical risk factors for lower extremity injuries in our male soldiers, who are regularly required to perform landing tasks from obstacles of various heights during military training or exercises. The results of this study collectively established that the peak resultant GRF possessed a strong exponential regression relationship with landing height, while knee flexion angles (at initial contact and peak GRF) and peak knee flexion angular velocities followed an inverse-exponential relationship with landing height, and peak knee joint power adopted a simple linear regression relationship with landing height. The parameters analyzed in this study are highly dependent on landing height. The exponential increase in peak GRF and the relatively slower increase in knee flexion angles, angular velocities and joint power may synergistically lead to an exacerbated lower extremity injury risk at large landing heights. The prior regression study revealed how the landing height can directly influence the magnitude of peak GRF, knee flexion angles, angular velocities and joint power; however, based on previous landing studies, there is still a lack of understanding of how the knee joint will respond in terms of the kinematics and energetics to the combined effects of different landing heights and techniques. The next study in Stage A sought to examine the knee joint kinematics and energetics sustained during landing phase, in response to the effects of landing height (0.3m and 0.6m) and technique (single-leg and double-leg landing). The key observations of the study were as follows: 1) heightened peak GRF during single-leg landing and/or at greater landing height, 2) higher knee flexion angles and angular velocities during double-leg landing and/or at greater landing height, and 3) elevated joint power and eccentric work done during double-leg landing and/or at larger landing height. 152 The range of peak GRF obtained in the current study is consistent with several previous studies that examined GRF during single-leg and double-leg landing techniques. Pappas et al. (2007) observed a higher GRF at 40-deg knee flexion for the dominant limb during single-leg landing than double-leg landing from a 0.4-m height. Similarly, in the current study, a greater peak resultant GRF was obtained for singleleg landing than double-leg landing for both 0.3-m and 0.6-m landing heights. McNitt-Gray (1993), and Seegmiller and McCaw (2003) reported an increase in peak GRF when the landing height was elevated during double-leg landing. The findings added that the aggravation in peak GRF with increased landing height was generally present for both double-leg and single-leg landing, though it was statistically significant only during single-leg landing. The greater GRF noted for single-leg landing from both landing heights suggested that the single-leg landing technique may involve a larger lower extremity injury risk, relative to double-leg landing. Double-leg landing generally allows elevated knee flexion angles throughout the landing phase of double-leg landing compared to single-leg landing (Pappas et al., 2007); moreover, Madigan and Pidcoe (2003) reported that the range of motion for knee flexion were greater for double-leg landings. The results revealed that this elevation in knee flexion angles was further enhanced when the landing height was increased. This observation indicated that the knee joint is able to respond more effectively in terms of kinematics against GRF during double-leg landing, compared to single-leg landing. The response was exhibited in the form of increased knee flexion angles during landing phase in order to promote shock attenuation as the knee joint is known to be partly responsible for the body's ability to absorb shock during ground contact (DeVita and Skelly, 1992; Hargrave et al., 2003). 153 On the other hand, the presence of a larger peak GRF during single-leg landing is attributed, in part, to a diminished capacity for shock attenuation. DeVita and Skelly (1992) reported that a soft landing style produces a mitigated GRF compared to stiff landing. Seegmiller and McCaw (2003) further suggested gymnasts tended to land with minimal knee flexion and thus incurred higher GRF than recreational athletes. Hence, the presence of lower knee flexion during single-leg landing can lead to a reduced shock absorption capacity, wherein the knee joint will sustain large compressive impact loads (Jeffrey and Aspden, 2006; Lafortune et al., 1996; Yeow et al., 2008) which can potentially inflict cartilage lesions (Coventry et al., 2006; Madigan and Pidcoe, 2003; Hargrave et al., 2003) and also place the ACL at a higher risk for injury (Lephart et al., 2002; Olsen et al., 2004; Yeow et al., 2008; Boden et al., 2000). In terms of knee flexion angular velocity, double-leg landing permitted a substantially greater angular velocity compared to single-leg landing; furthermore, it was noted that the angular velocity markedly increased with landing height during double-leg landing. These findings demonstrated that the knee joint was able to respond with relatively more immediacy to the landing impact via active knee flexion, during double-leg landing. It was also observed that the increment in landing height could also facilitate the escalation of this response. Yu et al. (2006) have previously demonstrated that the knee flexion angular velocity has a negative correlation with peak GRF during landing, thus indicating that active knee flexion is a key factor in impact force attenuation. In this study, the presence of a larger knee flexion angular velocity and lower peak GRF during double-leg landing clearly illustrated enhanced shock attenuation, relative to single-leg landing. Furthermore, the increased knee 154 flexion angular velocity is necessary to cope with the elevated GRF that arises from the increment in landing height. Similar to knee flexion angular velocity, a greater negative knee joint power was found during double-leg landing than single-leg landing; the negative joint power also increased significantly with landing height during double-leg landing. DeVita and Skelly (1992) reported that the presence of a negative knee joint power indicated eccentric work done on knee extensors to dissipate impact energy. Zhang et al. (2000) further illustrated an increase in negative knee joint power with landing height, which suggested that the knee extensors were key contributors to energy dissipation during landing. The results showed that the increment in landing height increased the negative joint power during double-leg landing, which implied elevated eccentric work done on the knee extensors. The findings of this study also demonstrated that the eccentric work done was elevated by 90.2% when the landing height increased from 0.3-m to 0.6-m during double-leg landing, but only a smaller increase of 59.9% was noted for single-leg landing. In addition, at the 0.3-m landing height, the eccentric work done decreased by 43.2% during single-leg landing, relative to double-leg landing; the reduction was further aggravated to 52.3% for the 0.6-m landing height. The findings suggest that the knee joint was able to respond with greater energy dissipation during double-leg landing than single-leg landing, at both tested landing heights, and this may be attributed to the reduced knee joint kinematics in the latter landing technique. A main limitation of this study is that the present study was conducted in a controlled laboratory environment where the subjects were briefed on the requirements of the trials and knew what to expect. Although this study allows reasonable comparison of GRF, knee joint kinematics and energetics between landing 155 heights and between landing techniques as all subjects performed the same set of tasks, the results may not completely reflect the physiological landing maneuver during sports- or military-related landing activities. A physiological landing maneuver can involve unexpected factors, such as friction of landing surface, type of shoe/boots, upper body motion and additional weights carried, that can render the landing more unpredictable and risky than a simple landing technique in a controlled laboratory. It should be acknowledged that the motion-capture system has an innate degree of error in kinematics measurement during rapid human motion. Though every effort was made to ensure minimal marker motion, it is still possible that the limitations of the instrumentation may affect the results to some extent. Additionally, the unilateral development of certain overuse and acute lower extremity injuries suggests that the lower extremity function may not be completely bilaterally symmetrical. Schot et al. (1994) reported the presence of bilateral asymmetry among left and right side vertical GRFs and lower extremity joint moments during double-leg landing from a 0.6-m height. It should be noted that the main aim of this study was not to examine the bilateral differences in double-leg landing, but to investigate the effect of different landing techniques on lower extremity biomechanical parameters. We therefore selected biomechanical data from the dominant limb to allow consistent comparison between single-leg and double-leg landing tasks. The results collectively indicated that an increase in landing height and/or the use of the single-leg landing technique aggravated the peak GRF during landing phase. Moreover, the knee joint displayed greater knee flexion angles at initial contact and at peak GRF, and maximum knee flexion during double-leg landing, compared to single-leg landing. The knee joint further exhibited elevated knee flexion angles at 156 11) Axial Tibial Rotation Restraint (Tibial attachment base extension) (Arc block for inserting restrain studs) 242 12) Brace Cuffs (Thigh) (Shank) 243 13) Brace Components (Tibia) (Femur) 244 14) Tibial Contact Layer 15) Ankle Adaptor 245 16) Shoe Connector 246 A.3. Procedures for determining ATT and ATR using reference markers (1) Base marker placement from the Plug-in Gait Marker Set (2) Reference marker placement 247 (3) Generation of tibial and femoral segments using base and reference markers, followed by referencing of segment orientation to respective epicondyle markers in static trial (4) Removal of epicondyle markers in dynamic trial. Referencing relationships were used to ‘re-create’ epicondyle markers and generate origin markers for tibial and femoral segment, which were required for forming the respective coordinate systems 248 Vicon Bodylanguage code to establish referencing relationships ** Create ankle joint centre from lateral and medial malleoli ** RAJC = (RANK+RT3)/2 ** Create femur and tibia segment ** FemSeg = [RF3,RF1-RF2,RF2-RTHI,zxy] TibSeg = [RANK,RT2-RAJC,RAJC-RTIB,zxy] ** Reference femur and tibia segments to lateral femoral and tibial epicondyle markers respectively ** RKNE = {-30,-40,-55}*FemSeg RT1 = {-35,-30,360}*TibSeg ** Output femoral and tibial epicondyle marker positions in 3D workspace ** OUTPUT(RKNE, RT1) Vicon Bodylanguage code to calculate ATT and ATR ** Establish segment widths ** RFemW = ($MarkerDiameter+$RKneeWidth)/2 RTibW = ($MarkerDiameter+$RKneeWidth)/2 ** Generate femoral and tibial origin markers ** RFO = CHORD(RFemW,RKNE,RHJC,RTHI) RTO = CHORD(RTibW,RKT1,RAJC,RTIB) ** Output femoral and tibial origin marker positions in 3D workspace ** OUTPUT(RFO,RTO) ** Create femoral and tibial coordinate systems ** RFemCS = [RFO,RHJC-RFO,RFO-RKNE,zxy] RTibCS = [RTO,RTO-RAJC,RTO-RKT1,zxy] ** Determine ATT from relative displacements between tibial and femoral origin markers, transformed onto the tibial coordinate system ** ATT = RFO/RTibCS-RTO/RTibCS ** Determine ATT from Euler angles between tibial and femoral origin markers , transformed onto the tibial coordinate system ** ATR = - ** Output ATT and ATR ** OUTPUT(ATT, ATR) 249 CHAPTER 11 PUBLICATION LIST ~ Persist and persevere, and you will find most things that are attainable, possible ~ Lord Chesterfield 250 10. PUBLICATION LIST Journals 1) C.H. Yeow, C.H. Cheong, K.S. Ng, P.V.S. Lee, J.C.H. Goh, 2008. Anterior cruciate ligament failure and cartilage damage during knee joint compression: a preliminary study based on the porcine model. American Journal of Sports Medicine 36: 934-42. 2) J.C.H. Goh, C.H. Yeow, 2008. Biomechanics at Macro to Nano-scale Levels. International Journal of Applied Biomedical Engineering 1: 7-13. 3) C.H. Yeow, S.K. Rubab, P.V.S. Lee, J.C.H. Goh, 2009. Inhibition of anterior tibial translation or axial tibial rotation prevents anterior cruciate ligament failure during impact compression. American Journal of Sports Medicine 37: 813-21. 4) C.H. Yeow, S.T. Lau, P.V.S. Lee, J.C.H. Goh, 2009. Damage and degenerative changes in menisci-covered and exposed tibial osteochondral regions after simulated landing impact compression – a porcine study. Journal of Orthopaedic Research 27: 1100-8. 5) C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2009. Regression relationships of landing height with ground reaction forces, knee flexion angles, angular velocities and joint powers during double-leg landing. The Knee 16: 381-6. 6) C.H. Yeow, K.S. Ng, C.H. Cheong, P.V.S. Lee, J.C.H. Goh, 2009. Repeated application of incremental landing impact loads to intact knee joints induces anterior 251 cruciate ligament failure and tibiofemoral cartilage deformation and damage: a preliminary cadaveric investigation. Journal of Biomechanics 42: 972-81. 7) C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2009. Effect of landing height on frontal plane kinematics, kinetics and energy dissipation at lower extremity joints. Journal of Biomechanics 42: 1967-73. 8) C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2009. Sagittal knee joint kinematics and energetics in response to different landing heights and techniques. The Knee. [Epub ahead of print] PMID: 19720537 9) C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2009. Direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact. Journal of Biomechanics. [Epub ahead of print] PMID: 19863961 10) C.H. Yeow, Y.H. Ng, P.V.S. Lee, J.C.H. Goh, 2009. Tibial cartilage damage and deformation at peak displacement compression during simulated landing impact. American Journal of Sports Medicine (Accepted). Conferences 1) ‘Biomechanical analysis of the knee joint during drop-landing’. Singapore Orthopaedic Association 29th Annual Scientific Meeting 2006. Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 252 2) ‘Mechanism of anterior cruciate ligament failure during impact compression of the knee joint’. Biomedical Engineering Society (Singapore) 4th Scientific Meeting 2007. Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh. (Gold Award – Postgraduate Category) 3) ‘Investigation of the non-contact landing knee injury guideline: a porcine knee impact study’. Biomedical Engineering Society (Singapore) 4th Scientific Meeting 2007. Authors: K.S. Ng, C.H. Yeow, P.V.S. Lee, J.C.H. Goh. (Silver Award – Undergraduate Category) 4) ‘Tibial contact forces during high-speed compression of the knee joint’. XXI International Society of Biomechanics Congress 2007 (Taipei). Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh, 2007. Proceedings of XXI Congress of the International Society of Biomechanics 40(S2): S145. 5) ‘Load threshold for anterior cruciate ligament failure in jump landing’. XXI International Society of Biomechanics Congress 2007 (Taipei). Authors: C.H. Cheong, C.H. Yeow, K.S. Ng, P.V.S. Lee, 2007. Proceedings of XXI Congress of the International Society of Biomechanics 40(S2): S242. 6) ‘Anterior cruciate ligament failure during impact compression of the knee joint’. 3rd WACBE World Congress on Bioengineering 2007 (Bangkok). Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh. 253 7) ‘Tibial contact forces during impact compression of the knee joint’. 3rd Asian Pacific Conference on Biomechanics 2007 (Tokyo). Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh, 2007. Proceedings of AP Biomech (JSME): #160. 8) ‘Tibial contact loading during double-leg drop-landing’. 3rd Asian Pacific Conference on Biomechanics 2007 (Tokyo). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2007. Proceedings of AP Biomech (JSME): #161. 9) ‘Investigation of tibiofemoral cartilage damage during anterior cruciate ligament failure from impact compression of cadaveric knee joint’. 54th Annual Meeting of the Orthopaedic Research Society 2008 (San Francisco). Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh, 2008. ORS transactions 33: 0643. 10) ‘Post-traumatic knee injuries following impact loads’. 7th Asian Pacific Conference on Medical and Biological Engineering (Beijing). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2008. IFBME Proceedings (APCMBE). 11) ‘Pathomechanics of post-traumatic knee injuries’. 4th International Conference on Biomedical Engineering (Kuala Lumpur). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2008. IFBME Proceedings (Biomed 2008). 254 12) ‘Investigation of tibiofemoral cartilage damage during anterior cruciate ligament failure from impact compression of cadaveric knee joint’. 16th Congress for European Society of Biomechanics 2008 (Lucerne). Authors: C.H. Yeow, K.S. Ng , C.H. Cheong, P.V.S. Lee, J.C.H. Goh, 2008. 13) ‘Role of Bioengineering in Surgery’. 33rd Annual Scientific Meeting of The Royal College of Surgeons of Thailand. Jul 2008 (Pattaya). Authors: J.C.H. Goh, C.H. Yeow. Surgical Practice in the Present Era. P142 14) ‘Landing Impact Loads Predispose Osteocartilage to Degeneration’. 13th International Conference on Biomedical Engineering. Dec 2008 (Singapore). Authors: C.H. Yeow, S.T. Lau, P.V.S. Lee, J.C.H. Goh, 2008. (Young Investigator Award – 3rd) 15) ‘Preventing Anterior Cruciate Ligament Failure During Impact Compression by Restraining Anterior Tibial Translation or Axial Tibial Rotation’. 13th International Conference on Biomedical Engineering. Dec 2008 (Singapore). Authors: C.H. Yeow, R.S. Khan, P.V.S. Lee, J.C.H. Goh, 2008. 16) ‘Restraining anterior tibial translation or axial tibial rotation during simulated landing impact prevents anterior cruciate ligament failure but aggravates cartilage damage’. 55th Annual Meeting of the Orthopaedic Research Society 2009 (Las Vegas). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh, 2009. 255 17) ‘ACL injury prevention during landing requires substantial inhibition of anterior tibial translation and axial tibial rotation using effective bracing’. 4th Asian Pacific Conference on Biomechanics 2009 (Christchurch). Authors: C.H. Yeow, W.L. Gan, James C.H. Goh. 18) ‘The role of impact loads on osteocartilage degeneration’. 4th WACBE World Congress on Bioengineering 2009 (Hong Kong). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 19) ‘Restraining anterior tibial translation during impact compression does not protect the anterior and posterior tibial osteochondral regions from damage and deformation’. 4th WACBE World Congress on Bioengineering 2009 (Hong Kong). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 20) ‘Inhibiting anterior tibial translation and axial tibial rotation protects the anterior cruciate ligament at the expense of femoral articular cartilage’. XXII International Society of Biomechanics Congress 2009 (Cape Town). Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 21) ‘Inhibition of anterior tibial translation or axial tibial rotation prevents anterior cruciate ligament failure during simulated landing impact, but does not protect the tibiofemoral osteochondral tissue from damage and deformation’. 2nd HOPE Meeting 2009 (Hakone), Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 256 22) ‘"Inhibition of anterior tibial translation or axial tibial rotation prevents anterior cruciate ligament failure during simulated landing impact but does not protect the tibiofemoral osteochondral tissue from damage and deformation’. 3rd East Asian Pacific Student Workshop on Nano-Biomedical Engineering 2009 (Singapore), Authors: C.H. Yeow, P.V.S. Lee, J.C.H. Goh. 257 [...]... the hip, 29.0% for the knee and 4 .3% for the ankle during double-leg landing During single-leg landing, the contributions decreased to 36 .6% for the hip, increased to 60.7% for the knee and decreased to 2.7% for the ankle during single-leg landing These findings emphasized the roles of the hip and knee as the dominant energy dissipaters in the sagittal plane for double-leg landing, which was in line...peak GRF and maximum knee flexion angles during double-leg landing with increased landing height The findings illustrated that the knee joint delivered larger knee flexion angular velocity, negative knee joint power and eccentric work done during double-leg landing, than single-leg landing, at both heights Altogether, the knee joint is able to respond more effectively in terms of kinematics and energetics... 70-deg flexion to simulate a landing posture Hewett et al (1996) reported that the knee may be flexed 60-80 deg during jump -landing while Devita and Skelly (1992) found that stiff-style 169 landing, compared to soft-style landing, generated a greater peak ground impact and a flexed knee position at impact, which averaged 77deg Hence, the knee posture of 70deg was chosen for the impact compression trials... associated with landing height and landing technique The next question would be – how much does the knee joint contribute to the total energy dissipation compared to other lower extremity joints during impact landing? Currently, there is limited understanding on the differences in energy dissipation strategies adopted by the lower extremity joints between single-leg and double-leg landing maneuvers... (2007), Kernozek et al (2008), McNitt-Gray (19 93) , and Self and Paine (2001) have previously reported that recreational athletes tended to adopt a landing strategy with relatively higher hip and knee flexion It was also observed that the hip and knee attained larger joint angles at initial contact and peak joint angles during double-leg landing than single-leg landing in the sagittal plane; however, this... energetics to a larger landing impact from an elevated height during double-leg landing, compared to single-leg landing This allows better shock absorption and thus minimizes the risk of sustaining lower extremity injuries From the previous two studies in Stage A, it was found that the knee serves to provide shock absorption for the landing impact and the energy dissipation capacity of the knee joint is strongly... plane for single-leg landing, (3) the hip was the main contributor to energy dissipation in the frontal plane for double-leg landing, and (4) the knee was the chief contributor to energy dissipation in the frontal plane for single-leg landing 157 In both double-leg and single-leg landing, it was noted that the hip and knee generally achieved greater joint angles at initial contact and peak joint angles... absorbing the landing impact Finally, it was demonstrated in this study that in the sagittal plane, the hip and the knee showed major contributions to energy dissipation for double-leg landing, but for single-leg landing, the hip and the ankle were the dominant energy dissipaters Additionally, in the frontal plane, the hip acted as the key energy dissipater during double-leg landing, while the knee contributed... strategies in ACL injury prevention, such as improvement of brace designs, should also examine and alleviate the damage profile of the cartilage during impact landing Armed with the test protocol for applying simulated landing impact to porcine specimens, it was subsequently translated for use with cadaveric specimens Therefore, the next study in Stage B aimed to investigate the effect of landing impact. .. data on joint power and eccentric work demonstrated 35 .1% for the hip, 35 .3% for the knee and 29.7% for the ankle in terms of contribution to total energy dissipation in the sagittal plane during double-leg landing However, it should be noted that the contributions increased to 42.9% for the hip, decreased to 11.4% for the knee and increased to 45.7% for the ankle during single-leg landing For the frontal . peak GRF during single-leg landing and/ or at greater landing height, 2) higher knee flexion angles and angular velocities during double-leg landing and/ or at greater landing height, and 3) elevated. single- leg landing than double-leg landing for both 0 .3- m and 0.6-m landing heights. McNitt-Gray (19 93) , and Seegmiller and McCaw (20 03) reported an increase in peak GRF when the landing height. examine the knee joint kinematics and energetics sustained during landing phase, in response to the effects of landing height (0.3m and 0.6m) and technique (single-leg and double-leg landing) .