Hip and knee functions are intimately connected and reduced hip abductor function might play a role in development of knee osteoarthritis (OA) by increasing the external knee adduction moment during walking. The purpose of this study was to test the hypothesis that reduced function of the gluteus medius (GM) muscle would lead to increased external knee adduction moment during level walking in healthy subjects. Reduced GM muscle function was induced experimentally, by means of intramuscular injections of hypertonic saline that produced an intense short-term muscle pain and reduced muscle function. Isotonic saline injections were used as non-painful control. Fifteen healthy subjects performed walking trials at their self-selected walking speed before and immediately after injections, and again after 20 min of rest, to ensure pain recovery. Standard gait analyses were used to calculate three-dimensional trunk and lower extremity joint kinematics and kinetics. Surface electromyography (EMG) of the glutei, quadriceps, and hamstring muscles were also measured. The peak GM EMG activity had temporal concurrence with peaks in frontal plane moments at both hip and knee joints. The EMG activity in the GM muscle was significantly reduced by pain (-39.6%). All other muscles were unaffected. Peaks in the frontal plane hip and knee joint moments were significantly reduced during pain (-6.4% and -4.2%, respectively). Lateral trunk lean angles and midstance hip joint adduction and knee joint extension angles were reduced by 1 degrees . Thus, the gait changes were primarily caused by reduced GM function. Walking with impaired GM muscle function due to pain significantly reduced the external knee adduction moment. This study challenge the notion that reduced GM function due to pain would lead to increased loads at the knee joint during level walking.

OBJECTIVE: Use of ultrasound Doppler (USD) in diagnosing and treatment monitoring of patients with RA has increased considerably. Hyperaemia is an integral part of the inflammatory response, and the amount of USD activity in an inflamed synovium may therefore be used to quantify the inflammatory activity. It is unclear, however, whether the hyperaemia alone reflects the disease activity or may be influenced by other factors.

METHODS: Twenty-nine patients with RA underwent USD examination of the wrist before and immediately after three interventions. The interventions were carried out on three separate days. The interventions were (i) isometric exercise of the muscles of the hand and forearm, (ii) heating and (iii) cooling of the hand. The amount of Doppler in the wrist joint was quantified by measuring the percentage of colour in the synovium-the colour fraction (CF). The CF values estimated before and after each intervention were compared to see if any intervention affected the amount of Doppler in the synovium.

RESULTS: The CF decreased significantly after cooling of the hand (P = 0.018 and <0.0001). Despite being highly significant, the numerical decrease in CF was only modest, 0.78-1.33 percentage points. The other interventions did not affect the CF significantly, with P-values of 0.65 and 0.59 in the heating intervention and 0.49 in the exercise intervention.

CONCLUSIONS: Cooling of the hand should, if possible, be avoided before a USD examination of the wrist in patients with RA, because the amount of Doppler activity might be affected by low skin temperatures.