TEPStabil - Muscle Function and Dynamic and Postural Stability in Patients Receiving Hip or Knee Arthroplasty

Muscle strength in knee flexion and extension and hip abduction will be tested using using a dynamometer (Biodex System 4 Pro: Biodex Medical Systems, Shirley, NY, USA)

Instrumented gait analysis on an overground walkway with two embedded force plates (Kistler force plate 9260AA6, Kistler AG, Winterthur, Switzerland; sampling rate 2400 Hz) and on a treadmill with an embedded plantar pressure plate (h/p/cosmos, Zebris FDM-T, Isny, Germany)

The overall stability index (OSI) will be assessed using the Biodex Balance System SD (Biodex Medical Systems, Inc., Shirley, NY, USA) and is determined by the variance in platform displacement from the horizontal plane.

Overall health will be assessed using the EQ-5D-5L health questionnaire

Site specific pain and function will be assessed with the Hip Osteoarthritis Outcome Score (HOOS) and Knee Injury and Osteoarthritis Outcome Score (KOOS) depending on the affected joint (hip or knee).

Surface electrodes (Ag/AgCl, Noraxon, U.S.A. Inc., Scottsdale, AZ, USA: 10 mm diameter, 22 mm inter-electrode distance) will be placed bilaterally on glutaeus medius, vastus medialis, semitendinosus, tibialis anterior, gastrocnemius medialis, and peroneus longus muscles. Periods of muscle activity will be defined as intensity above 2 Standard Deviation (SD) of the resting Electromyography (EMG) signal. Duration of overlapping muscle activity between agonists and antagonists normalized to one gait cycle or of a balance test, respectively, will be determined.

Passive range of motion will be assessed for ankle plantar-/dorsiflexion, knee flexion/extension and hip flexion/extension, ab/adduction, internal/external rotation using goniometers and recorded in degrees. The range between two maxima will be recorded.