Effect of Action Observation and Motor Imagery on Arthrogenic Muscle Inhibition of the Quadriceps in Patients With End-stage Knee Gonarthrosis.

The study aims at evaluating the effects of one session of Action Observation Training (AOT) and Motor Imagery (MI) on arthrogenic muscle inhibition (AMI) of the quadriceps (QF) in subjects with end-stage gonarthrosis.

30 patients with end-stage knee osteoarthritis were enrolled. Patients were randomized in two groups (experimental group and control group).

Experimental group performed one AOT and MI session with motor content of concentric and isometric QF contractions, whereas control group underwent a 6-minute sham AOT and MI session. Every patient was evaluated to assess the percentage of AMI on the QF before (T0) and after (T1) the assigned treatment following the gold standard Twitch Interpolated Technique. Both groups sat on an isometric dynamometric chair (COR1, OT-Bioelettronica, Torino) with a load cell (FORZA, OT-Bioelettronica, Torino) designed to detect and map the strenght generated by the QF muscle. Upper body movements were limited by crossover shoulder harnesses, a belt across the abdomen and the subjects were asked to keep their arms crossed holding onto the harness while performing the evaluation.

Three large electrodes (10x13cm) were positioned over the quadriceps muscle belly. Two sEMG electrodes (FREEEMG, BTS, Italy) were positioned on the Vastus Medialis and Vastus Lateralis using the SENIAM protocol.

Right after the first evaluation (T0), both groups performed an AOT session. The experimental group was shown a video (4 minutes) in which a subject (matched for age, sex, and limb affected) performed, in third person view, quadriceps concentric contractions for 2 minutes and isometric contractions for 2 minutes. The video contained visual elements indicating the maximality of the effort. After both concentric movement video and isometric movement video the subjects performed a MI session (2 sessions, 1 minute in length each), in which they were asked to imagine in first person the action just seen in the video.