J. Aaboe

Weight loss is effective for symptomatic relief in obese subjects with knee osteoarthritis independently of joint damage severity assessed by high-field MRI and radiography

OBJECTIVE With an increasing prevalence of older and obese citizens, the problems of knee osteoarthritis (KOA) will escalate. Weight loss is recommended for obese KOA patients and in a majority of cases this leads to symptomatic relief. We hypothesized that pre-treatment structural status of the knee joint, assessed by radiographs, 1.5 T magnetic resonance imaging (MRI) and knee-joint alignment, may influence the symptomatic changes following a significant weight reduction. DESIGN Patients were recruited from a Department of Rheumatology. Eligibility criteria were age above 50 years, body mass index ≥ 30 kg/m(2), primary KOA diagnosed according to the American College of Rheumatology (ACR) criteria and having verified structural damage. Patients underwent a 16 weeks dietary programme with formula products and counselling. MRI and radiographs of the most symptomatic knee were obtained at baseline and assessed for structural damage using the Boston-Leeds Osteoarthritis of the Knee Score, minimum joint space width and Kellgren-Lawrence score. Imaging variables, muscle strength and degree of alignment, were examined as predictors of changes in Knee Osteoarthritis Outcome Score (KOOS) and Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) - Osteoarthritis Research Society International (OARSI) Responder Criterion. RESULTS Structural damage at baseline assessed by imaging, muscle strength or knee-joint alignment showed no statistically significant association to changes in KOOS pain and function in daily living (r ≤ 0.13; P>0.05) or the OMERACT-OARSI Responder Criterion (OR 0.48-1.68; P-values ≥ 0.13). CONCLUSIONS Presence of joint damage did not preclude symptomatic relief following a clinically relevant weight loss in older obese patients with KOA. Neither muscle strength nor knee-joint alignment was associated with the degree of symptomatic relief.

Adaptations in the gait pattern with experimental hamstring pain

Pain changes movement but most studies have focused on basic physiological adaptations during non-functional movement tasks. The existing studies on how pain affects lower extremity gross movement biomechanics have primarily involved movements in which the quadriceps is the primary muscle and little attention has been given to how pain in other muscles affects functional movement. The purpose of this study was to investigate the changes in the gait patterns of healthy subjects that occur during experimental muscle pain in the biceps femoris. In a cross-over study design, 14 healthy volunteers underwent EMG assisted 3D gait analyses before, during and after experimental biceps femoris pain induced by intramuscular injections of hypertonic saline. Isotonic saline injections were administered as a non-painful control. The experimental biceps femoris pain led to reductions in hip extensor moments, knee flexor and lateral rotator moments. No changes in lower extremity kinematics and EMG activity in any of the recorded muscles were observed. It is concluded that experimental muscle pain in the biceps femoris leads to changes in the gait pattern in agreement with unloading of the painful muscle. The changes are specific to the painful muscle. The present study provides support to the theory that musculoskeletal pain is a protective signal leading to changes in movement patterns that serve to unload the painful tissue.

Obesity and Walking: Implications for Knee Osteoarthritis and Plantar Heel Pain

Obesity is closely associated with a multitude of musculoskeletal conditions. Many musculoskeletal diseases, including knee osteoarthritis and foot pain, are commonly thought to be related to mechanical overload, and the link to obesity intuitively supports such a notion. Walking is significantly changed in the presence of obesity—changes that are similar to those associated with physical disability among individuals in need of personal assistance in daily life. However, although obesity, osteoarthritis, and other painful musculoskeletal conditions exhibit similar changes in locomotion biomechanics, longitudinal data that confidently demonstrate a causal biomechanical link between obesity and osteoarthritis and plantar fasciitis do not exist and are needed to design better and rational treatments of patients with coexistence of obesity and musculoskeletal disorders.

Quadriceps-strengthening exercise and quadriceps and knee biomechanics during walking in knee osteoarthritis: A two-centre randomized controlled trial

Objective: To assess the effect of quadriceps strengthening on quadriceps muscle force, power, and work and tibio‐femoral compressive loads during walking in adults with knee osteoarthritis. Methods: Study design: Two‐center, randomized, controlled trial. Intervention: Patients with knee osteoarthritis were randomly allocated to quadriceps strengthening program (3 times weekly) or no attention control group. Main outcome measures: Primary outcome was change from baseline in peak quadriceps force during walking at 12 weeks. Secondary outcomes included quadriceps power and work, knee compression forces during walking estimated with musculoskeletal modeling, muscle strength and pain and function. Outcomes were measured at baseline and 12 weeks. Results: 30 patients were randomized to receive either training (n = 15) or no attention (n = 15). At follow‐up, there were no statistical differences between groups for maximum quadriceps force, quadriceps positive power, negative work, and positive work, and knee compressive force. Maximum negative quadriceps power in early stance was statistically significantly increased 36% in the training group compared to the control group which was most likely partially a response to faster walking velocity at follow‐up. Muscle strength and patient reported pain and function were improved in the training group compared to the control group. Conclusions: Quadriceps strength training leads to increased muscle strength and improved symptomatic and functional outcomes but does not change quadriceps or knee joint biomechanics during walking. The biomechanical mechanism of improved health with strength training in knee osteoarthritis patients remains unknown. ClinicalTrials.gov Identifier: NCT01538407.

140 RELATIONSHIP BETWEEN SUBMAXIMAL QUADRICEPS FORCE CONTROL AND JOINT LOADS DURING WALKING IN KNEE OSTEOARTHRITIS

The changes in knee joint adduction moments were consistent with the changes observed in less severe OA (Figure 2), as were the changes in the sagittal plane moments. Conclusions: This study shows that pain induced changes in knee joint mechanics during walking replicate changes observed in less severe patients. The experimental model may be used to study knee OA pathomechanics and possible preventive measures against abnormal joint loading in knee OA. It is suggested that pain management regimes be tested on the basis of their influence on knee OA pathomechanics. 140

139 GAIT CHANGES IN PATIENTS WITH KNEE OSTEOARTHRITIS ARE REPLICATED BY EXPERIMENTAL KNEE PAIN

Objective. Medial knee osteoarthritis (OA) is characterized by pain and associated with abnormal knee moments during walking. The relationship between knee OA pain and gait changes remains to be clarified, and a better understanding of this link could advance the treatment and prevention of disease progression. This study investigated changes in knee moments during walking following experimental knee pain in healthy volunteers, and whether these changes replicated the joint moments observed in medial knee OA patients. Methods. In a crossover study, 34 healthy subjects were tested on 3 different days; gait analyses were conducted before, during, and after pain induced by hypertonic saline injections (0.75 ml) into the infrapatellar fat pad. Isotonic saline and sham injections were used as control conditions. Peak moments in frontal and sagittal planes were analyzed. The results were compared with data from 161 medial knee OA patients. The patients were divided into less severe OA and severe OA categories, which was based on radiographic disease severity of the medial compartment. Results. Experimental knee pain led to reduced peak moments in the frontal and sagittal planes in the healthy subjects, which were similar to the patterns observed in less severe OA patients while walking at the same speed. Conclusion. In healthy subjects, pain was associated with reductions in knee joint moments during walking in a manner similar to less severe knee OA patients. The experimental model may be used to study mechanically-driven knee OA progression and preventive measures against abnormal joint loading in knee OA.