Femoral Translation in Patients with Unicompartmental Osteoarthritis—A Cohort Study

Ci a ion: Wegne , M.; Kuwe , S.; K a zens ein, S.; Simon, M.J.K.; Mo adi, B. Femo al T ansla ion in Pa ien s wi h Unicompa men al Os eoa h i is—A Coho S udy. Biomechanics 2024,4, 428–438. h ps://doi.o g/10.3390/ biomechanics4030029 Academic Edi o : A kady Voloshin Recei ed: 20 May 2024 Re ised: 30 June 2024 Accep ed: 10 July 2024 Published: 12 July 2024 Copy igh : © 2024 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). A icle Femo al T ansla ion in Pa ien s wi h Unicompa men al Os eoa h i is—A Coho S udy Ma his Wegne 1,* , Simon Kuwe 1, S e an K a zens ein 2, Maciej J. K. Simon 1and Babak Mo adi 1 1Depa men o O hopedics and T auma Su ge y, Medical Uni e si y Cen e Schleswig-Hols ein—Campus Kiel, A nold-Helle -S asse 3, 24105 Kiel, Ge many; [email p o ec ed] (S.K.); [email p o ec ed] (M.J.K.S.); [email p o ec ed] (B.M.) 2CAU Mo ion Labo a o y, Kiel Uni e si y, Olshausens aße 74, 24098 Kiel, Ge many; [email p o ec ed] *Co espondence: [email p o ec ed]; Tel.: +49-431-500-24501 Abs ac : The use o h ee-dimensional (3D) gai analysis o image emo o ibial ansla ion can aid in he diagnosis o pa hology and p o ide addi ional insigh in o he se e i y o KOA (knee os eoa h i is). Femo o ibial ansla ion is o pa icula impo ance in pa ien s unde going UKA (unicompa men al knee a h oplas y), as he absence o elonga ion o ligamen ous s uc u es esul s in changes in he kinema ic alignmen . The aim o he s udy was o e alua e he pa ame e s o emo o ibial ansla ion in pa ien s wi h MOA (medial unicompa men al OA). An a i icial model was employed o de elop a me hod o calcula ing emo o ibial ansla ion in i o . In a p ospec- i e coho s udy, gai da a using h ee-dimensional gai analysis we e collec ed om 11 pa ien s ( 68.73 ±9.22 yea s ) wi h se e e OA scheduled o UKA and 29 unma ched heal hy pa icipan s ( 22.07 ±2.23 yea s ). The disc e e a iables cha ac e ising emo o ibial ansla ion we e compa ed o s a is ical signi icance (p< 0.05) using he S uden ’s - es and he Mann–Whi ney U- es . The esul s o he s udy alida ed an a i icial model o mimic emo o ibial ansla ion. The compa ison o pa- ien s scheduled o UKA and a heal hy unma ched con ol g oup showed no s a is ically signi ican di e ences conce ning emo o ibial ansla ion in all h ee planes (p> 0.05). Howe e , he PROMs (pa ien - epo ed ou come measu es), spa io empo al, and kinema ic pa ame e s showed s a is ically signi ican di e ences be ween he g oups (p< 0.001). The da a p esen ed he e demons a e ypical changes in PROMs as well as spa io empo al and kinema ic ou comes o MOA as seen in knee OA. The esul s o he clinical gai analyses demons a e indi idualised emo o ibial ansla ion. The ex en o indi idual emo o ibial ansla ion may p o e o be an impo an pa ame e o al e ed join kinema ics in pa ien s wi h MOA, especially p io o UKA implan a ion. Keywo ds: emo o ibial ansla ion; 3D gai analysis; knee os eoa h i is 1. In oduc ion Knee os eoa h i is (KOA) is he mos p e alen o m o os eoa h i is (OA) in he Wes e n wo ld. I is cha ac e ised by pain, swelling, s i ness and slow wea . KOA can esul in a loss o join unc ion and a signi ican educ ion in he quali y o li e o he a ec ed indi idual [ 1 ]. Among he h ee compa men s o he knees, KOA is mos com- monly obse ed in he medial compa men [ 2 – 5 ]. The cu en imaging p ocedu es o he diagnosis o KOA ( adiog aphy, compu ed omog aphy, magne esonance imaging) a e exclusi ely s a ic imaging echniques. Func ional changes associa ed wi h he disease canno be e alua ed [ 2 , 3 ]. The use o dynamic gai analysis has been es ablished as a diagnos ic ool o he iden i ica ion o kinema ic changes associa ed wi h KOA [ 3 , 4 , 6 , 7 ]. Reduced knee lexion a heel s ike, educed knee abduc ion angle a 50% o s ance phase and educed knee lexion ange du ing gai ha e been epo ed in pa ien s wi h KOA [ 8 ]. The emo al condyles’ ansla ion ela i e o he ibia has been he subjec o a limi ed Biomechanics 2024,4, 428–438. h ps://doi.o g/10.3390/biomechanics4030029 h ps://www.mdpi.com/jou nal/biomechanics Biomechanics 2024,4429 numbe o s udies, which ha e yielded he e ogeneous esul s [ 6 , 7 , 9 – 12 ]. Consequen ly, he ibio- emo al mo emen pa e ns emain a subjec o con en ion. Femo o ibial ansla ion is o c i ical impo ance in pa ien s wi h medial unicompa - men al knee os eoa h i is (MOA), as i is a key pa ame e e lec ing he abno mal loading and wea pa e ns o he a ec ed compa men o he knee join [ 3 ]. The inc eased shea o ces ha ac du ing his phase o he gai cycle esul in inc eased wea and ea , leading o g ea e ca ilage loss. This esul s in a change in he kinema ics o he knee join and a u he inc ease in emo o ibial ansla ion, which ep esen s a sign o ea ly os eoa h i is (OA) [6–8]. In ea ly MOA, mobile-bea ing UKA (unicompa men al knee a h oplas y) ep e- sen s a alid he apeu ic op ion wi h g ea ad an ages o pa ien s. The bea ing pe ec ly con o ms wi h emo al and ibial componen s and mo es comple ely passi ely be ween he emo al and ibial implan [ 13 ]. This esul s in almos physiologic knee kinema ics compa ed wi h o al knee a h oplas y (TKA) [ 14 , 15 ]. UKA in ol es eplacing only he damaged compa men o he knee, hus p ese ing he heal hy bone, ca ilage, and lig- amen s. This leads o a mo e na u al knee unc ion pos -su ge y. Many pa ien s epo high le els o sa is ac ion wi h he ou comes o UKA, including imp o ed unc ion and quali y o li e. The UKA’s knee-spa ing app oach has led o an inc ease in he numbe o implan ed unicondyla endop os heses, which, in u n, has necessi a ed high-quali y su gical indica ions [ 13 , 16 – 19 ]. The kinema ic alignmen and, hus, he unc ion o he ligamen s uc u es in he knee join is o pa icula impo ance when de e mining he indica ion o su ge y and implan a ion o a UKA. A de iciency in he an e io c ucia e ligamen ha becomes appa en du ing su ge y has signi ican consequences o he pa ien , as he implan composi ion mus be al e ed o a o al knee a h oplas y (TKA) mus be employed [2,7,15]. I he indica ion is co ec , he kinema ically aligned UKA ep esen s an al e na i e knee p os hesis ha is mo e indi idualised, physiological and ana omical [ 17 ]. The abili y o adequa ely isualise emo o ibial ansla ion in a p eope a i e h ee-dimensional gai analysis would signi ican ly con ibu e o an e en mo e p ecise indica ion o he implan a- ion o a UKA. Consequen ly, he de elopmen o indi idualised implan s in a h oplas y would be u he ad anced. Gi en he g owing numbe o kinema ically aligned UKAs, i becomes e iden ha a unc ional assessmen o he MOA is necessa y. The objec i e o ou s udy was o in es iga e he di e ences in emo o ibial ansla ion in pa ien s unde going planned UKA. 2. Ma e ials and Me hods The da a used in his s udy we e collec ed in an in i o se ing and a clinical case- con ol s udy. In he i s pa , an a i icial model was used o de elop a me hod o calcula ing emo o ibial ansla ion in i o using 3D gai analysis. In he second pa o he s udy, he e icacy o a me hod o isualising emo o ibial ansla ion using 3D kinema ic mo ion analysis was e alua ed. This was pe o med h ough a p ospec i e coho s udy ha pe o med an in aindi idual compa ison o a g oup wi h MOA in which UKA is indica ed. This was ollowed by a compa ison wi h a heal hy con ol g oup. Emphasis was placed on he loading esponse in he s ance phase o he gai cycle [ 8 ]. In ou se ing, he loading esponse was de ined as he i s 12% o he gai cycle. Ini ial con ac was iden i ied using kinema ic-based e en de ec ion. 2.1. Model Analysis Fo calcula ing emo o ibial ansla ion in i o , a i ual ma ke wi hin he ibial pla eau was c ea ed by using he analogue ma ke placemen s on he medial and la e al edges o he ibia and se ing he i ual ma ke o hal he dis ance be ween hem, whe e emo o ibial ansla ion was expec ed o be he la ges . An ana omical a i icial bone model wi h an implan ed medial mobile-bea ing UKA wi h a emo able inlay was used. A coo dina e sys em was compiled a he dis al end o he emu . The i ual ma ke is Biomechanics 2024,4430 illus a ed in Figu e 1. To assess emo o ibial ansla ion, he mo emen o he i ual ibial ma ke was eco ded in he local emo al coo dina e sys em and calcula ed as ROM in he loading esponse o he an e io –pos e io , medio–la e al, and c anio–caudal axes o he a e aged mo emen . Biomechanics 2024, 5, FOR PEER REVIEW 3 A coo dina e sys em was compiled a he dis al end o he emu . The i ual ma ke is illus a ed in Figu e 1. To assess emo o ibial ansla ion, he mo emen o he i ual ib- ial ma ke was eco ded in he local emo al coo dina e sys em and calcula ed as ROM in he loading esponse o he an e io –pos e io , medio–la e al, and c anio–caudal axes o he a e aged mo emen . Figu e 1. Ma ke sys em wi h he i ual ibial ma ke (blue). In he in i o model, he diffe ences be ween a physiological and a pa hological mo emen wi h inc eased emo o ibial ansla ion we e eco ded using an ana omic model o he knee wi h he implan ed mobile-bea ing UKA, a emo able inlay and sp ings applied o mimic ligamen ension [20]. 2.2. Clinical S udy F om 2021 un il 2022, pa ien s wi h an indica ion o a medial UKA a a uni e si y medical cen e we e included in he p ospec i e coho s udy. Pa icipan s comple ed he ollowing ques ionnai es, including pa ien - epo ed ou come measu es (PROMs): he Ox o d Knee Sco e (OKS) [21], he Knee Socie y Sco e (KSS) [22], he Uni e si y o Cali- o nia a Los Angeles (UCLA) Ac i i y Scale, he Nume ic Ra ing Scale (NRS) o pain [23] and he Sho Fo m 12 Ques ionnai e (SF-12) [24]. 2.3. Rec ui men and Inclusion C i e ia Inclusion c i e ia o he MOA g oup consis ed o se e e unila e al os eoa h i is o he medial compa men classi ied using he Kellg en–Law ence classi ica ion [25] o he Ahlbäck classi ica ion [26] wi h ull- hickness a icula ca ilage loss (‘bone on bone’). In all pa ien s in he p eope a i e examina ion, he an e io c ucia e ligamen and he medial and la e al colla e al ligamen s we e unc ionally in ac , he algus de o mi y was manu- ally co ec able and he e was no e idence o OA in he la e al knee compa men . Rheu- ma oid a h i is, ixed algus de o mi y (e.g., >15°), lexion de o mi y > 15°, o he inabili y o walk 6 min wi hou an assis i e de ice was conside ed a con aindica ion. The con ol Figu e 1. Ma ke sys em wi h he i ual ibial ma ke (blue). In he in i o model, he di e ences be ween a physiological and a pa hological mo emen wi h inc eased emo o ibial ansla ion we e eco ded using an ana omic model o he knee wi h he implan ed mobile-bea ing UKA, a emo able inlay and sp ings applied o mimic ligamen ension [20]. 2.2. Clinical S udy F om 2021 un il 2022, pa ien s wi h an indica ion o a medial UKA a a uni e si y medical cen e we e included in he p ospec i e coho s udy. Pa icipan s comple ed he ollowing ques ionnai es, including pa ien - epo ed ou come measu es (PROMs): he Ox o d Knee Sco e (OKS) [ 21 ], he Knee Socie y Sco e (KSS) [ 22 ], he Uni e si y o Cali o nia a Los Angeles (UCLA) Ac i i y Scale, he Nume ic Ra ing Scale (NRS) o pain [23] and he Sho Fo m 12 Ques ionnai e (SF-12) [24]. 2.3. Rec ui men and Inclusion C i e ia Inclusion c i e ia o he MOA g oup consis ed o se e e unila e al os eoa h i is o he medial compa men classi ied using he Kellg en–Law ence classi ica ion [ 25 ] o he Ahlbäck classi ica ion [ 26 ] wi h ull- hickness a icula ca ilage loss (‘bone on bone’). In all pa ien s in he p eope a i e examina ion, he an e io c ucia e ligamen and he medial and la e al colla e al ligamen s we e unc ionally in ac , he algus de o mi y was manually co ec able and he e was no e idence o OA in he la e al knee compa men . Rheuma oid a h i is, ixed algus de o mi y (e.g., >15 ◦ ), lexion de o mi y > 15 ◦ , o he inabili y o walk 6 min wi hou an assis i e de ice was conside ed a con aindica ion. The con ol Biomechanics 2024,4431 g oup consis ed o young and heal hy subjec s. Excluded we e pa icipan s wi h p io knee su ge y and unc ional limi a ions in he knee. 2.4. Mo ion Analysis To e alua e kinema ic join pa ame e s, spa io empo al pa ame e s we e collec ed, and emo o ibial ansla ion and gai analysis we e pe o med using he Op iT ack 3D mo ion analysis sys em (Na u alPoin Inc., Co allis, OR, USA) wi h a eco ding equency o 100 Hz and he “705 CST P o o m” eadmill. Thi een e lec i e ma ke s we e a ached wi h adhesi e ape o ana omical landma ks on each leg [ 27 ] (Figu e 2). The eco dings we e managed using ‘Cap u e2D™’ ( 1.0.0.194, C-Mo ion Inc., Boyds, MD, USA) [ 20 ]. A lowpass Bu e wo h il e wi h a h eshold o 6 Hz o he i s o de was applied o p ocess and analyse he eco ded da a, and missing da a we e in e pola ed up o 10 ames using Visual 3D P o essional™ ( 1.0.0.194, C-Mo ion Inc., Boyds, MD, USA). All pa icipan s walked o wa d and we e eco ded o 30 s. Biomechanics 2024, 5, FOR PEER REVIEW 4 g oup consis ed o young and heal hy subjec s. Excluded we e pa icipan s wi h p io knee su ge y and unc ional limi a ions in he knee. 2.4. Mo ion Analysis To e alua e kinema ic join pa ame e s, spa io empo al pa ame e s we e collec ed, and emo o ibial ansla ion and gai analysis we e pe o med using he Op iT ack 3D mo ion analysis sys em (Na u alPoin Inc., Co allis, OR, USA) wi h a eco ding e- quency o 100 Hz and he “705 CST P o o m” eadmill. Thi een e lec i e ma ke s we e a ached wi h adhesi e ape o ana omical landma ks on each leg [27] (Figu e 2). The e- co dings we e managed using ‘Cap u e2D™’ ( 1.0.0.194, C-Mo ion Inc., Boyds, MD, USA) [20]. A lowpass Bu e wo h il e wi h a h eshold o 6 Hz o he i s o de was applied o p ocess and analyse he eco ded da a, and missing da a we e in e pola ed up o 10 ames using Visual 3D P o essional™ ( 1.0.0.194, C-Mo ion Inc., Boyds, MD, USA). All pa icipan s walked o wa d and we e eco ded o 30 s. (a) (b) Figu e 2. Re lec ing ma ke s used o gai analysis: (a) on al iew; (b) sagi al iew. 2.5. Mo ion Assessmen P io o eco ding gai and unning analyses, an accele a ion-based unc ional cali- b a ion p ocedu e was pe o med each ime. Pa icipan s began walking on he eadmill a a sel -selec ed speed. Pa icipan s had a six-minu e pe iod o habi ua ion o walking on he eadmill o ule ou bias due o al e ed gai pa e n [28]. A e a com o able walking speed was es ablished, he in es iga o eco ded a leas 23 walking cycles on he eadmill a e signalling he pa icipan . Spa io empo al mo ion pa ame e s, as well as he ROM in all h ee axes, we e eco ded pe pa icipan . In all eco dings, he used ma ke sys em had a esidual o 1.2 mm. 2.6. S a is ical Analysis S a is ical analysis was pe o med by using Jamo i o Windows (The Jamo i p ojec (2022), Ve sion 2.2.5, www.jamo i.o g accessed on 7 May 2023). Fo no mal dis ibu ion, Figu e 2. Re lec ing ma ke s used o gai analysis: (a) on al iew; (b) sagi al iew. 2.5. Mo ion Assessmen P io o eco ding gai and unning analyses, an accele a ion-based unc ional calib a- ion p ocedu e was pe o med each ime. Pa icipan s began walking on he eadmill a a sel -selec ed speed. Pa icipan s had a six-minu e pe iod o habi ua ion o walking on he eadmill o ule ou bias due o al e ed gai pa e n [28]. A e a com o able walking speed was es ablished, he in es iga o eco ded a leas 23 walking cycles on he eadmill a e signalling he pa icipan . Spa io empo al mo ion pa ame e s, as well as he ROM in all h ee axes, we e eco ded pe pa icipan . In all eco dings, he used ma ke sys em had a esidual o 1.2 mm. Biomechanics 2024,4432 2.6. S a is ical Analysis S a is ical analysis was pe o med by using Jamo i o Windows (The Jamo i p ojec (2022), Ve sion 2.2.5, www.jamo i.o g accessed on 7 May 2023). Fo no mal dis ibu ion, he Shapi o–Wilk es was pe o med. The S uden ’s - es and he Mann–Whi ney U- es we e used o es o s a is ical signi icance. The signi icance le el was de ined as p< 0.05. Fo mul iple es ing, he Bon e oni co ec ion was applied [29]. 3. Resul s 3.1. In Vi o Analysis The ROM o he ibial ma ke in he loading esponse phase o he gai cycle is shown in Table 1. The collec ed esul s a y when a i icial ligamen ension is applied o he inlay is emo ed. Table 1. Range o he emo o ibial ansla ion in he a i icial model o a knee. Values a e gi en as mean ±s anda d de ia ion (SD). Range o Mo ion Medio–La e al An e io –Pos e io C anio–Caudal mean ±SD [mm] 2.05 ±1.05 2.25 ±0.55 2.18 ±0.57 inlay−/s ings+ 1.11 1.58 1.34 inlay−/s ings−3.14 2.31 2.43 inlay+/s ings+ 1.21 2.92 2.47 inlay+/s ings−2.75 2.21 2.50 3.2. Case–Con ol S udy A o al o 40 pa icipan s we e included in he s udy. The MOA g oup consis ed o 11 pa ien s (3 women, 8 men) wi h se e e MOA scheduled o unicompa men al knee eplacemen su ge y. The con ol g oup con ained 29 heal hy pa icipan s (16 women, 13 men). Demog aphic da a a e shown in Table 2. Table 2. Demog aphics o he pa icipan s. Values as mean ±s anda d de ia ion (SD). Pa ame e s Con ol G oup MOA G oup age [yea s] 22.07 ±2.23 68.73 ±9.22 heigh [cm] 175.76 ±7.79 179.27 ±7.96 weigh [kg] 69.91 ±12.43 88.27 ±17.75 BMI 1[kg/m2]22.5 ±2.83 27.52 ±5.59 1Body mass index. The MOA g oup showed signi ican di e ences in he KSS (p< 0.001), OKS (p< 0.001), UCLA Ac i i y Scale (p< 0.001), NRS o pain (p< 0.001) and SF-12 Physical Componen Summa y (PCS) (p< 0.001) o he con ols. The SF-12 Men al Componen Summa y (MCS) showed no signi ican di e ences (p= 0.785). The absolu e alues a e shown in Table 3. Table 3. Sco es o he pa icipan s in he case–con ol s udy. Values a e gi en as mean ±SD. Sco es [Range] Con ol G oup MOA G oup p-Value KSS 1[0–200] 195.5 ±8.38 126.73 ±42.54 <0.001 OKS 2[12–60] 12.20 ±0.95 31.40 ±4.92 <0.001 UCLAAS 3[1–10] 9.66 ±1.04 6.36 ±1.03 <0.001 NRS 4[0–10] 0.35 ±0.90 5.36 ±1.86 <0.001 SF-12 PCS 556.80 ±2.37 38.6 ±8.48 <0.001 SF-12 MCS 654.20 ±6.94 54.10 ±10.40 0.785 1 Knee Socie y Sco e. 2 Ox o d Knee Sco e. 3 UCLA Ac i i y Scale. 4 Nume ic Ra ing Scale. 5 Sho Fo m 12-I em Heal h Su ey Physical Componen Summa y. 6 Sho Fo m 12-I em Heal h Su ey Men al Componen Summa y. Biomechanics 2024,4433 The spa io empo al pa ame e s o he MOA g oup showed a signi ican educ ion in speed (1.23 ± 0.16 m/s s. 0.86 ± 0.31 m/s, p< 0.001) and s ide leng h (1.4 ± 0.16 m s. 1.0 ± 0.28 m, p< 0.001) compa ed o he con ol g oup (Table 4). S ide equency was no signi ican ly di e en (105.0 ± 6.5 s eps/min s. 99.0 ± 15.9 s eps/min, p= 0.074). The ROM o lexion signi ican ly dec eased h oughou he gai cycle o bo h legs ( p< 0.001 ). Loading esponse changes in lexion di e ences we e no s a is ically signi i- can ( p= 0.074 le , p= 0.096 igh ). The di e ences in ROM o abduc ion/adduc ion we e no signi ican . Table 4. Spa io empo al and kinema ic pa ame e s in he case–con ol s udy. Pa ame e s Side Con ol G oup MOA G oup p-Value eloci y [m/s] 1.23 ±0.16 0.86 ±0.31 <0.01 *,1 cadence [1/min] 105.00 ±6.50 99.00 ±15.9 0.07 1 s ide leng h [m] 1.40 ±0.16 1.02 ±0.28 <0.01 *,1 ROM lexion [◦] ull gai cycle le 62.57 ±6.99 50.00 ±7.61 <0.01 *,1 igh 62.58 ±6.32 52.40 ±6.58 <0.01 *,1 ROM lexion [◦] loading esponse le 9.34 ±3.81 7.10 ±7 6.59 0.07 2 igh 12.35 ±4.43 10.50 ±8.95 0.09 2 ROM ab-/adduc ion [◦] ull gai cycle le 12.03 ±3.97 9.16 ±2.90 0.04 1 igh 11.74 ±4.03 8.24 ±2.99 0.01 1 ROM ab-/adduc ion [◦] loading esponse le 3.78 ±1.89 2.59 ±1.50 0.07 2 igh 3.57 ±1.46 3.00 ±1.82 0.18 2 Mean ± s anda d de ia ion, ROM = ange o mo ion, * s a is ical signi icance, 1 S uden ’s - es , 2 Mann–Whi ney U- es . Femo o ibial ansla ion in he loading phase was no signi ican ly di e en be ween he MOA g oup and he con ol g oup (Table 5). The 4% gai cycle ime shi was applied o he da a p io o analysis. Table 5. Femo o ibial ansla ion in he loading esponse. Axis Side Con ol G oup MOA G oup p-Value medio–la e al [mm] le 5.2 ±2.9 4.1 ±2.6 0.27 1 igh 6.6 ±4.5 4.6 ±3.6 0.18 2 an e io –pos e io [mm] le 8.6 ±4.4 7.4 ±5.0 0.46 1 igh 8.6 ±5.3 9.7 ±7.5 0.79 2 c anio–caudal [mm] le 2.6 ±1.5 3.5 ±2.8 0.16 1 igh 4.5 ±2.4 5.1 ±3.6 0.56 1 Mean ±SD, 1S uden ’s - es , 2Mann–Whi ney U- es . Di e ences be ween he pa ien s’ legs we e conside ed. In he medio–la e al axis, ansla ion was 3.2 ± 2.0 mm in he diseased limb and 5.5 ± 3.6 mm in he heal hy limb ( p= 0.065 ). An e io –pos e io ansla ion was 8.2 ± 3.6 mm (diseased limb) and 9.0 ±8.4 mm (heal hy limb) (p= 0.562). Fo supe io –in e io , ansla ion was 3.5 ±2.3 mm (diseased limb) and 5.2 ± 3.9 mm (heal hy limb) (p= 0.401). The in aindi- idual compa ison showed no s a is ically signi ican di e ences. A la ge in aindi idual a ia ion o emo o ibial ansla ion in he an e io –pos e io plane is exempla ily shown in Figu e 3. Biomechanics 2024,4434 Biomechanics 2024, 5, FOR PEER REVIEW 7 (a) (b) Figu e 3. Femo o ibial ansla ion in he loading esponse phase ( i s 12% o he gai cycle) in he an e io –pos e io plane o he case–con ol s udy: (a) con ol g oup; (b) MOA g oup. 4. Discussion OA is one o he mos common causes o pain ul loss o mobili y in many popula ions [30,31]. Biological, mechanical and s uc u al componen s a e associa ed wi h OA as a dis- ease o he whole join [2]. An in e play o me abolic and mechanical changes and changes in he le els o in lamma o y cy okines [6] leads o an o e all change in he kinema ics o he join as an exp ession o he clinical p og ession o OA. As he se e i y o OA co e- sponds wi h he exp ession o kinema ic changes [14], he iming o diagnosis and in e - en ion is essen ial o pa ien s’ ou comes [2]. Gai analysis can be used o iden i y unc ional changes in knee kinema ics in pa ien s wi h KOA. Dec eased knee lexion and p olonged heel s ike du ing he loading esponse phase o he gai cycle a e signs o ea ly OA [8]. The me hodical app oach ca ied ou in his s udy demons a es ha small dec eases in ligamen ension esul in a highe em- o o ibial ansla ion du ing he loading esponse phase as a possible indica o and ea ly sign o changed knee kinema ics in OA esul ing in mechanical changes (Figu e 3). To p o e ha inc eased emo o ibial ansla ion is p esen in pa ien s wi h se ious KOA and can be subs an ia ed by 3D gai analysis and demons a ed among o he ypical KOA changes, we ca ied ou a ield ial using a eadmill algo i hm and a ma ke -based analy ic sys em [32]. Ou expe imen al design was con i med by mul iple eco dings, e- sul ing in a low a iance o da a. In ecen yea s, ma ke less mo ion analysis me hods and in e ac i e measu emen sys ems ha e been gaining g ound. The in eg a ion o a i icial in elligence in o mo ion analysis opens up he possibili y o pe o ming mo ion analysis wi h less da a acquisi ion and p ocessing ime compa ed o ma ke -based me hods [33]. Ne e heless, we chose o eco d he gai o pa ien s wi h KOA using a ma ke -based sys- em because he de e mina ion o join cen es and join angles wi h a ma ke less sys em is no ye accu a e enough o clinical applica ions. The esul s o his s udy demons a e and con i m os eoa h i ic changes in se e e unicompa men al medial OA gai [15]. Signi ican changes in spa io empo al and kine- ma ic pa ame e s ypical o pa ien s wi h MOA we e ound. These included educed speed, educed s ide leng h and educed ROM o knee lexion [8–13]. Diffe ences in ca- dence and s ide leng h and ROM o abduc ion/adduc ion we e no s a is ically signi i- can . Recen s udies ha e demons a ed gai abno mali ies in os eoa h i ic join s using ma ke less 3D gai analysis and wea able senso s [34,35]. Boekes eijn (e al.) (2022) showed spa io empo al changes and compensa o y mechanisms ypical o OA and we e able o objec i ely assess he gai pa e n using an ine ial measu emen sys em in a clini- cal se ing. Wang (e al.) (2024) ound he amoun o knee lexion du ing inline lunging o be ano he po en ial indica o o knee os eoa h i is using a ma ke less mo ion cap u e sys em [35]. Figu e 3. Femo o ibial ansla ion in he loading esponse phase ( i s 12% o he gai cycle) in he an e io –pos e io plane o he case–con ol s udy: (a) con ol g oup; (b) MOA g oup. 4. Discussion OA is one o he mos common causes o pain ul loss o mobili y in many popula ions [30,31] . Biological, mechanical and s uc u al componen s a e associa ed wi h OA as a disease o he whole join [ 2 ]. An in e play o me abolic and mechanical changes and changes in he le els o in lamma o y cy okines [ 6 ] leads o an o e all change in he kinema ics o he join as an exp ession o he clinical p og ession o OA. As he se e i y o OA co esponds wi h he exp ession o kinema ic changes [ 14 ], he iming o diagnosis and in e en ion is essen ial o pa ien s’ ou comes [2]. Gai analysis can be used o iden i y unc ional changes in knee kinema ics in pa ien s wi h KOA. Dec eased knee lexion and p olonged heel s ike du ing he loading esponse phase o he gai cycle a e signs o ea ly OA [ 8 ]. The me hodical app oach ca ied ou in his s udy demons a es ha small dec eases in ligamen ension esul in a highe emo o ibial ansla ion du ing he loading esponse phase as a possible indica o and ea ly sign o changed knee kinema ics in OA esul ing in mechanical changes (Figu e 3). To p o e ha inc eased emo o ibial ansla ion is p esen in pa ien s wi h se ious KOA and can be subs an ia ed by 3D gai analysis and demons a ed among o he ypical KOA changes, we ca ied ou a ield ial using a eadmill algo i hm and a ma ke -based analy ic sys em [ 32 ]. Ou expe imen al design was con i med by mul iple eco dings, esul ing in a low a iance o da a. In ecen yea s, ma ke less mo ion analysis me hods and in e ac i e measu emen sys ems ha e been gaining g ound. The in eg a ion o a i icial in elligence in o mo ion analysis opens up he possibili y o pe o ming mo ion analysis wi h less da a acquisi ion and p ocessing ime compa ed o ma ke -based me hods [ 33 ]. Ne e heless, we chose o eco d he gai o pa ien s wi h KOA using a ma ke -based sys em because he de e mina ion o join cen es and join angles wi h a ma ke less sys em is no ye accu a e enough o clinical applica ions. The esul s o his s udy demons a e and con i m os eoa h i ic changes in se e e unicompa men al medial OA gai [ 15 ]. Signi ican changes in spa io empo al and kine- ma ic pa ame e s ypical o pa ien s wi h MOA we e ound. These included educed speed, educed s ide leng h and educed ROM o knee lexion [ 8 – 13 ]. Di e ences in cadence and s ide leng h and ROM o abduc ion/adduc ion we e no s a is ically signi ican . Recen s udies ha e demons a ed gai abno mali ies in os eoa h i ic join s using ma ke less 3D gai analysis and wea able senso s [ 34 , 35 ]. Boekes eijn (e al.) (2022) showed spa io em- po al changes and compensa o y mechanisms ypical o OA and we e able o objec i ely assess he gai pa e n using an ine ial measu emen sys em in a clinical se ing. Wang (e al.) (2024) ound he amoun o knee lexion du ing inline lunging o be ano he po en ial indica o o knee os eoa h i is using a ma ke less mo ion cap u e sys em [35]. Biomechanics 2024,4435 When looking a PROMs, ou coho displays di e ences om he con ol g oup in all sco es speci ic o knee unc ion, con i ming ha ou MOA coho had signi ican ly wo se knee unc ion and physical heal h. MOA pa ien s did no show any impai men s ega ding hei men al heal h despi e hei ad anced KOA. O e all, ou MOA coho was ep esen a i e o pa ien s wi h KOA [36]. The hypo hesis ha an os eoa h i ic knee would ha e a g ea e emo o ibial ans- la ion han an una ec ed knee was no con i med. Ou s udy design may ha e led o g oup e ec s due o signi ican di e ences in demog aphics (age, weigh , BMI). Inc easing age in luences he spa io empo al pa ame e s o gai , as ageing leads o educed join mobili y and a dec ease in muscle mass. Inc eased weigh , and consequen ly inc eased BMI, inc eases join loading and g ound eac ion o ces, which can lead o al e ed gai pa e ns in people wi h highe BMI. When high BMI and olde age a e combined, hei e ec s on gai may be exace ba ed and esul in a unc ional decline [37–39]. The e we e no s a is ically signi ican di e ences in emo o ibial ansla ion be ween he con ol and MOA g oups. This is consis en wi h he da a om Fa e (e al.) (2014), who we e unable o de ec an e io displacemen o he emu in pa ien s wi h se e e OA. [ 40 ]. In hei s udy on he ela ionship be ween he Kellg en–Law ence sco e and 3D kinema ic gai analysis, Zeng (e al.) (2017) obse ed ha in a Chinese popula ion su e ing om KOA, he e was inc eased emo al ansla ion an e io ly and dis ally a heel s ike. In a ecen s udy by Pos olka (e al.) (2020), he au ho s demons a e ha he ansla ion be ween he wo emo al condyles and he ibia is highly ask-dependen and indi idualised. They also s a e ha u he esea ch is needed o cla i y he ole o limb alignmen on knee join kinema ics, which is consis en wi h ou indings. The s udy indica es ha he selec ion o implan s o a h oplas y should be indi idualised, aking in o accoun he ecogni ion o knee join kinema ics p io o su ge y. This app oach may acili a e u he imp o emen s in a h oplas y ou comes. In he cu en s udy, no ele an di e ences be ween he le and igh sides we e iden- i ied (Table 5). I is no iceable ha he sca e o he da a is la ge in ou s udy popula ion. This means ha he e is a la ge in e indi idual a ia ion in emo o ibial ansla ion as well, wi hou a speci ic pa e n being ecognisable o KOA (Figu e 3). Fu he mo e, he e is no ele an di e ence in emo o ibial ansla ion be ween he heal hy and diseased limbs in he MOA g oup. This is in con as o a s udy by Zeng (e al.) (2024), which demons a ed inc eased emo o ibial ansla ion in ACL-de icien knees wi h ca ilage lesions compa ed o ACL-de icien knees wi hou ca ilage lesions in pa ien s wi h pos - auma ic os eoa h i- is (PTOA). These esul s could ha e signi ican implica ions o u u e indica ions o UKA o TKA and suppo he need o p eope a i e kinema ic analysis in pa ien s wi h MOA, especially in PTOA [7]. KOA is no limi ed o one limb, as p e iously desc ibed by Pe y (1992) and Good- ellow (e al.) (2015). KOA al e s mechanical and kinema ic pa e ns in mo emen as a sys emic disease; hus, he impai ed unc ion o one leg leads o an al e ed gai pa e n in bo h legs [2,8,15]. The indings o his s udy mus be in e p e ed in he con ex o i s limi a ions. T eadmill walking p o ides con olled and epea able condi ions, ye i can al e na u al gai pa e ns and esul in slowe gai speed and sho e s ide leng h [ 41 ]. This is a bias in ou s udy ha mus be aken in o accoun when in e p e ing he esul s. Skin ma ke s we e used o eco d he mo emen s; howe e , ma ke placemen is known o be able o bias da a. In ou eco dings, he used ma ke sys em had a esidual o 1.2 mm, which led o unce ain y. This p oblem is p esen in any ma ke -based mo ion cap u e sys em and canno be excluded. The e o e, his inaccu acy o 1.2 mm o he emo o ibial ansla ion could ha e caused bias and de aul ed in o no signi ican a iances be ween heal hy and unheal hy join s. Thi dly, he numbe o pa icipan s was limi ed o n = 40, and he g oups we e no age-ma ched. We unde s and ha he g oups a e di icul o compa e, bu he goal was o eco d a heal hy knee and compa e i wi h se e e OA o he knee; he e o e, we decided o include young and heal hy pa icipan s in he con ol g oup despi e he age di e ences and possible bias. Biomechanics 2024,4436 5. Conclusions The cu en esul s co obo a e he ypical changes obse ed in PROMs, as well as he spa io empo al and kinema ic esul s associa ed wi h MOA, as e idenced by he gai changes ypically obse ed in pa ien s wi h KOA. Howe e , clinical gai analyses e ealed no signi ican di e ence in emo o ibial ansla ion du ing he loading esponse phase o s ance. The ex en o indi idual emo o ibial ansla ion may p o e o be an impo an pa ame e o al e ed join kinema ics in pa ien s wi h MOA, especially p io o UKA implan a ion. In he u u e, he ex en o emo o ibial ansla ion may p o ide aluable in o ma ion o he diagnosis, ea men and moni o ing o MOA. Au ho Con ibu ions: Concep ualisa ion, S.K. (Simon Kuwe ), M.W., S.K. (S e an K a zens ein) and B.M.; me hodology, S.K. (Simon Kuwe ) and S.K. (S e an K a zens ein); so wa e, S.K. (Simon Kuwe ) and S.K. (S e an K a zens ein); alida ion, S.K. (Simon Kuwe ), S.K. (S e an K a zens ein), M.W. and B.M.; o mal analysis, S.K. (Simon Kuwe ); in es iga ion, S.K. (Simon Kuwe ); esou ces, S.K. (S e an K a zens ein); da a cu a ion, S.K. (Simon Kuwe ); w i ing—o iginal d a p epa a ion, S.K. (Simon Kuwe ); w i ing— e iew and edi ing, S.K. (Simon Kuwe ), M.W., S.K. (S e an K a zens ein), M.J.K.S. and B.M.; isualisa ion, S.K. (Simon Kuwe ); supe ision, B.M.; p ojec adminis a ion, S.K. (S e an K a zens ein) and B.M. All au ho s ha e ead and ag eed o he published e sion o he manusc ip . Funding: This esea ch ecei ed no ex e nal unding. Ins i u ional Re iew Boa d S a emen : The s udy was conduc ed in acco dance wi h he Decla a ion o Helsinki and app o ed by he Ins i u ional E hics Commi ee o Kiel Uni e si y (D536/21). In o med Consen S a emen : In o med consen was ob ained om all subjec s in ol ed in he s udy. Da a A ailabili y S a emen : Da a a e con ained wi hin he a icle. Con lic s o In e es : The au ho s decla e no con lic s o in e es . Re e ences 1. Felson, D.T. os eoa h i is o he knee. N. Engl. J. Med. 2006,354, 841–848. [C ossRe ] 2. Good ellow, J. Unicompa men al A h oplas y wi h he Ox o d Knee, 2nd ed.; Good ellow Publishe s Limi ed: Ox o d, UK, 2015. 3. Zeng, X.; Ma, L.; Lin, Z.; Huang, W.; Huang, Z.; Zhang, Y.; Mao, C. Rela ionship be ween Kellg en-Law ence sco e and 3D kinema ic gai analysis o pa ien s wi h medial knee os eoa h i is using a new gai sys em. Sci. Rep. 2017,7, 4080. 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