S228 Poster Presentations / Osteoarthritis and Cartilage 18, Supplement 2 (2010) S45–S256 507 EFFECT OF INTENSIFIED HOME-BASED EXERCISE AFTER TOTAL HIP REPLACEMENT - A CLINICAL RANDOMISED CONTROLLED TRIAL L.R. Mikkelsen 1 , S.S. Mikkelsen 1 , F.B. Christensen 2 1 Silkeborg Regional Hosp., Silkeborg, Denmark; 2 Faculty of Hlth.Sci., Aarhus Univ., Aarhus, Denmark Purpose: Total Hip Replacement (THR) is a common procedure with around 8000 operations per year in Denmark. Although a successful procedure, deficits in muscle strength and physical function 1-2 years after THR has been documented. There is a lack of evidence concerning which rehabili- tation strategy is the most effective in the early phase after THR and the amount of rehabilitation needed after THR surgery. The aim of this study was to investigate whether an intensified home-based rehabilitation strat- egy is effective in improving muscle strength and functional performance after THR. Methods: Forty-four patients who underwent fast track THR surgery between Sep 2008 and Jan 2009 completed the study (96% follow up). Par- ticipants were randomly assigned to an intervention group (IG) receiving 12 weeks of intensified training (e.g. rubber band resistance) or a control group (CG) receiving standard rehabilitation consisting of exercises without external resistance. Both groups were instructed in the exercises by a phys- iotherapist during their hospital stay and continued their training at home. The participants underwent 10 m walk test, one legged stance, hip abductor muscle strength test and fulfilled 3 questionnaires before surgery and again 4 and 12 weeks after. The questionnaires measured health related quality of life (EQ-5D), physical activity (PAS) as well as patient-evaluated function, stiffness and pain (WOMAC). After the intervention period a questionnaire concerning patient satisfaction were sent to the participants by mail. Results: The participants performed the prescribed exercises 12 times per week (mean) in the CG and 10 times in the IG (p=0.37). There was significant increases in both groups in all the measurements during the 12 weeks of exercises, but no significant differences between the groups (p>0.05). All participants in the IG were satisfied or very satisfied with the exercises compared to 85% in the CG (p=0.095). Conclusions: This study did not document an additional effect of the intensified exercise program compared with the control group. However it was proven that patients undergoing THR surgery tolerated the intensified exercises without additional pain, with high compliance and with greater patient satisfaction. Neither the intensified protocol nor the standard re- habilitation was adequate in avoiding a decrease in muscle strength and functional performance or eliminating the side difference in hip abductor muscle strength after fast track THR. This underlines the need for super- vised training immediately after THR surgery to minimize the decrease in muscle strength and physical function in these first postoperative weeks and to enhance the symmetry in lower extremity muscle strength. 508 ISOKINETIC QUADRICEPS STRENGTH MEASUREMENTS DIFFER BY HAMSTRING CO-ACTIVATION LEVEL IN THE MULTICENTER OSTEOARTHRITIS (MOST) STUDY N.A. Segal 1 , L. Frey Law 1 , K. Wang 2 , J.C. Torner 1 , M. Nevitt 3 , C.E. Lewis 4 , D. Felson 2 1 Univ. of Iowa, Iowa City, IA; 2 Boston Univ., Boston, MA; 3 Univ. of California San Francsisco, San Francisco, CA; 4 Univ. of Alabama at Birmingham, Birmingham, AL Purpose: In the MOST Study, isokinetic quadriceps torque has been the pri- mary measure of strength. However, antagonistic hamstring co-activation could result in underestimation of quadriceps strength. If significant co- activation were present in those with lower measured quadriceps strength, future analyses of strength data may improve accuracy by controlling for muscle co-activation level. For this reason, there is a need to characterize whether the quadriceps strength measurement is inversely related to hamstring co-activation level. Secondly, since it is less resource inten- sive to measure muscle co-activation unilaterally, it would be helpful to assess to what extent hamstring co-activation level correlates between limbs. Finding a high correlation could enable contralateral extrapolation of co-activation levels, reducing participant measurement burden while maintaining analytic power. Methods: Participants in the MOST study, a study of those with or at high risk for symptomatic knee OA, completed surface electromyography of the medial and lateral hamstring muscles during maximal isokinetic quadriceps strength testing at 60 degrees/sec. Mean muscle activity during each repetition was standardized by maximum agonist activation levels (% maximum). Co-activation was assessed as the median hamstring ac- tivity (% maximum) during knee extension (antagonist activity) for each muscle group individually and combined, correcting for baseline error. After confirming linearity, we calculated correlations between measured peak quadriceps strength and hamstring co-activation level, while treating participant as a repeated factor. We assessed (1) the association between isokinetic quadriceps strength with antagonist hamstring co-activation, and (2) the correlation of hamstring co-activation between limbs. Results: For 480 subjects (524 limbs; 67.9% women) studied to date, the mean±SD age, BMI, peak isokinetic quadriceps and flexor strength were 61.6±7.8 years, 29.8±5.8 kg/m 2 , 85.0±32.5 Nm, and 57.5±20.9 Nm respectively. 65.8% of knees had Kellgren-Lawrence (KL) grade less than 2 at baseline and there was no association between KL grade (<2 vs. ≥2) and degree of hamstring co-activation (p>0.20). Mean±SD antagonist hamstring co-activation for the medial, lateral and combined hamstrings was 9.1±6.6%, 17.6±10.6%, and 13.3±7.3% respectively, and was negatively associated with peak quadriceps strength (all p<0.0003). For each 1% normalized median co-activation level, quadriceps strength measurements were 0.6, 0.8 and 1.1 Nm lower respectively, and this remained significant after multivariable adjustment (0.4-0.8 Nm lower) for each 1% antagonistic hamstring co-activation. Between limb hamstring antagonist co-activation level correlations were significant for the medial (r=0.38, p = 0.0102) and overall hamstring co-activation (r=0.45, p=0.0024), but not for the lateral (p > 0.05) hamstrings. Conclusions: Participants in the MOST cohort with higher levels of antag- onistic hamstring co-activation had, on average, 5-15 Nm less measured quadriceps strength. Analyses of quadriceps strength should be adjusted for level of hamstring co-activation. In addition, there is a moderate cor- relation between the composite co-activation of the hamstrings between limbs. Before assuming that this co-activation measure can be generalized to the contralateral limb, further study is indicated to confirm the strength of this correlation. 509 PATELLOFEMORAL JOINT OSTEOARTHRITIS AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION (HAMSTRING TENDON AUTOGRAFT): 5-10 YEAR FOLLOW-UP K.M. Crossley 1 , C. Lai 2 , M. Makdissi 1 , H.G. Morris 1 , M.G. Pandy 1 1 Univ. of Melbourne, Parkville, Australia; 2 Monash Univ., Clayton, Australia Purpose: Early tibiofemoral joint (TFJ) osteoarthritis (OA) frequently de- velops secondary to anterior cruciate ligament reconstruction (ACLR). The few studies that have evaluated patellofemoral joint (PFJ) reported a high prevalence of PFJ OA (∼46%) >7 years post surgery. Notably, these studies only followed up people who had a patellar tendon autograft, which is known to be associated with PFJ morbidity. This study aimed to: (i) describe the prevalence of radiographic PFJ and TFJ OA, 5-10 years after ACLR using a hamstring tendon autograft (HT); (ii) compare OA symptoms, anterior knee pain symptoms, ACLR outcome and activity levels between people with PFJ OA and those who were free of OA; and (iii) compare the range of knee motion and functional performance between people with PFJ OA and those with no OA. Methods: 70 people who had undergone an arthroscopic HT ACLR from a single surgeon 5-10 years previously were recruited and performed: (i) standard radiographs (postero-anterior to grade the TFJ, skyline to grade the PFJ) (ii) questionnaires including the Knee Osteoarthrits Outcome Score (KOOS), Anterior Knee Pain Scale (AKPS), Tegner Activity Scale, Inter- national Knee Documentation Committee (IKDC) Subjective Knee Form, International Physical Activity Questionnaire; (iii) range of knee movement and functional performance examination. Results: Of 70 participants, radiographic PFJ OA was evident in 47% (33/70) and radiographic TFJ OA was evident in 33% (23/70). In total, 48% (34/70) exhibited no radiographic evidence of either TFJ or PFJ OA. Of the 36 (51%) people with radiographic OA, isolated PFJ OA was the most common distribution (41%), followed by tri-compartmental distribution (31%), then lateral TFJ and PFJ distribution (13%) combined medial TFJ and PFJ (8%) and isolated TFJ (8%). Between-group comparisons revealed no differences age, height, weight or activity level for people with PFJ OA than those with no radiographic OA. People with radiographic PFJ OA had significantly worse scores on the AKPS, IKDC and most scales of the KOOS than those without