Validity of algometry and video assessment to diagnose pain in sheep with knee synovitis

Reasons to perform study. To assess lameness in animals, semi-objective scales are used. Video
is sometimes used to enable blinding of the clinician. In addition, the assessment of pain is
particularly difficult in animals since they cannot report their feelings. The interpretation of the
reactions of the animals can be different between observers. A method to quantify pain is the
measure of mechanical nociceptive thresholds (MNT), a method called algometry. Since
synovitis is often linked to swelling of periarticular tissues and to synovial fluid effusion,
palpation of the joint is also a useful test. The objectives of the current study were to assess in
sheep whether (1) video assessment of lameness is in agreement with real observation; (2)
algometry of the knee is correlated with lameness evaluation; (3) algometry is correlated with
identification of swelling by palpation. Material and methods. The population of sheep enrolled
in a controlled trial at the Ovine Research Center of UNamur was used for the current study.
Results. There was a moderate inter-rater agreement (value of kappa was 0,41) between the
experimenter who evaluated the ewes on site and the one who watched the videos. No significant
correlation was identified between lameness scores and algometry. A negative correlation
(algometry reactive threshold is lower when palpation score is higher) was identified between
palpation scores and MNT (P<0.05). Discussion. Video assessment can be used in research to
assess lameness. The experience of the observer must be taken into account. Algometry is not
entirely valid since an adaptation or learning process seems to develop in sheep.