Clinical signs and diagnosing osteoarthritis
OSTEOARTHRITIS (OA): PART 2 – DIAGNOSTICS
HISTORY and PHYSICAL EXAMINATION
Clinical signs in dogs with OA are of varying intensity, severity, frequency,
duration, and progression which are also influenced by lifestyle and the weather. Clinical
signs include exercise reluctance/reduction, exercise intolerance, inactivity stiffness,
lameness, gait alterations (such as “bunny-hopping”), the inability to jump up or down,
behavioral changes ( aggression, hunting, playing, sharpening claws, using the litter
tray, stairs/furniture usage, grooming (unkempt), etc.), muscle atrophy, and joint
The orthopedic examination includes evaluating gait analysis, muscle atrophy,
joint swelling, capsular and extracapsular fibrosis, joint effusion, altered joint range of
motion, joint manipulation pain, and crepitus.
Video telemedicine services like VetTriage.com can perform video evaluations of
your pet to avoid the difficulties associated with traveling to your veterinarian with an
arthritic pet, most of whom are larger sized, older dogs, and allow for further valuable
televet discussion and information (teleadvice).
Radiographs are utilized for a variety of benefits. A radiographic grade of OA
score has been used. The intra- and inter-observer measurement variability of the OA
stifle scoring system shows high reproducibility and low intra-observer variability.
Osteophytosis is associated with and seen with OA. As an example, osteophytosis
continues to progress post-operatively with cranial cruciate ligament rupture surgery,
especially the first 7 months post-operatively, and then between 7 and 13 months post-
operatively, with 45% of such dogs not showing progression on radiographs.
Radiographs can also depict enthesophytosis, joint effusion, soft tissue swelling,
subchondral sclerosis, intra-articular mineralization, subchondral cyst, and joint space
changes. Femoropatellar joint space increases with bodyweight and decreases with
There have been a number of surveys/questionnaires that have been reported
based on the owner assessments of their pets. The Liverpool Osteoarthritis in Dogs
(LOAD) survey, Canine Brief Pain Inventory (CBPI), & The American College of
Veterinary Surgeons' (ACVS) Canine Orthopaedic Index Questionnaire are three of
The CBPI owner-completed questionnaire quantifies the severity and impact of
chronic pain in dogs, and is available in French, Swedish, and English versions. The
CBPI has satisfying psychometric properties in terms of high internal consistencies and
ability to discriminate clinically sound dogs from OA dogs. However, based on the
confirmatory factor analysis, the original factor structure in the CBPI is not ideally suited
to measure pain related to OA.
The ACVS Canine Orthopaedic Index Questionnaire quantifies the quality of life
in dogs with orthopedic disease and its use has been validated.
Kinetic and kinematic analysis of dogs while climbing upstairs, walking down a
slope, sitting down, standing up, and walking has been reported and is scored using a
visual analog scale (VAS). The Hudson VAS is one example that has been reported.
Force platform gait analysis shows decreases in measurements after exercise in dogs
with pelvic limb OA.
A pressure algometer can be utilized to evaluate the effects of OA on
somatosensory processing in dogs using mechanical threshold testing. A pressure
algometer measures mechanical thresholds & can detect primary, and possibly
secondary, hyperalgesia in dogs with presumed OA.
Electrophysiological reflex measurements are more objective than behavioral
assessments; this data provides evidence of neurophysiological changes consistent
with central sensitization in dogs with spontaneous OA and demonstrates that canine
OA is associated with reduced diffuse noxious inhibitory controls.
Accelerometer-based technologies could be useful in providing objective
measures of canine ambulation, but most are either not tailored to the idiosyncrasies of
canine gait, or are un-validated or closed source approaches. Validated algorithms are
applied to accelerometer data for counting the number of steps and the distance
travelled by a dog.
Biomarkers have become increasingly studied with a variety of diseases in
veterinary medicine, including OA. Here are examples.
The plasma collagen marker procollagen type II propeptide (PIICP) differentiated
control dogs from those with canine hip dysplasia.
The concentration of TGF-β1 has also been measured in synovial fluid. An
increased TGF-β1 concentration is found in stifles affected with OA as a consequence
of cranial cruciate ligament rupture.
Serum and synovial fluid leptin concentrations do not predict radiographic
severity of canine OA but contribute to joint pain and dysfunction.
The protein constituents of synovial fluid samples from the stifle joints of dogs
with and without OA secondary to cranial cruciate ligament rupture show that the
median synovial fluid total protein and apo A-I concentrations for dogs with OA were
significantly greater than those for control dogs.
Serum C-telopeptide of type II collagen (CTX-II) and type X collagen (ColX)
levels are significantly higher in dogs with OA at weeks for up to 16 weeks post-
operative stifle surgery. As evaluated on MRI, the tibial plateau cartilage volumes in the
dogs with OA were significantly lower than in the control group as well. These tests can
be used to detect and monitor OA progression.
Synovial concentrations of monocyte chemoattractant protein (MCP)-1,
substance P, IL-6, IL-8, keratinocyte chemotactic-liken (KC-like), MMP-1, and MMP-3
were greater in OA than in normal joints. The synovial concentrations of bradykinin and
TIMP-4 were decreased in OA compared with normal joints. Synovial monocyte
chemoattractant protein 1 was identified as the most accurate marker to distinguish OA
from normal joints. No correlation was detected between any OA biomarker
concentration, individually or in combination, and severity of gait asymmetry at the walk.
Both the erythrocyte sedimentation rates and neutrophil/lymphocyte ratio might
be useful in monitoring progression of OA in dogs; both increased from over 12-weeks.
Arthroscopy is considered the most cost-effective method used to diagnosis OA
and perhaps the most valuable. It is minimally invasive, quick, and effective. It allows for
evaluation of the cartilage status, degree of synovial change, & the status of intra-
articular structures. The Outerbridge cartilage classification system and the Modified
Outerbridge scale are discontinuous ordinal scales used to grade chondropathy.
SYNOVIAL FLUID ANALYSIS
Synovial fluid analysis allows for collection of a total cell count and a differential cell
count. The normal joint has a total cell count of less than 2 x 10^9/L, a percent
mononuclear cell count of 94 to 100%, and a percent neutrophils 0 to 6%. An increase
in mononuclear cell numbers is seen with OA, with a total cell count of less than 2 to 5 x
10^9/L, a percent mononuclear cell count of 88 to 100%, and a percent neutrophils 0 to
Magnetic resonance imaging (MRI) is primarily utilized for soft tissue evaluation,
to characterize cartilage, ligaments, menisci, synovium, bone, & tendons Three-
dimensional reconstructed MRI using a quantitative technique of T2 mapping shows a
mean stifle cartilage volume in dogs weighing between 7.2 and 17.1 kg ranging from
319.7 to 647.3 mm3; while the mean knee cartilage surface area ranged from 427.14 to
757.2 mm2. There was evidence of both knee volume and surface area increasing
linearly with animal bodyweight. MRI T1ρ (spin-lattice relaxation in the rotating frame)
has been utilized to study tissue specific properties & reported for evaluation of articular
cartilage in the canine stifle.
CT is primarily utilized to evaluate bone and complex joints (elbows, carpi, and
tarsi). CT has high sensitivity for osteophytosis. Positive-contrast can be utilized to aid
Molecular imaging to assess stifle osseous metabolic changes serially was
successful in an in vivo canine model of post-traumatic osteoarthritis of the stifle utilizing
sodium fluoride (Na18F) positron emission tomography (PET)/CT coregistered with
MRI. Similarly, the use of 1 Fluorine-18-fluoro-2-deoxy-d-glucose (18F-FDG) PET/CT &
MRI assessed stifle 18F-FDG uptake in an in vivo acute cranial cruciate ligament canine
model, finding it to be highly sensitive for the detection of metabolic alterations in
osseous and nonosteochondral structures comprising the stifle joint.
FDG PET provides physiologic images of tissues based on their glucose
metabolism, and combined with CT. This detects soft tissue lesions in 40 to 64% of
dogs with OA. The FDG PET alone detected soft tissue lesions more than CT did
(100% versus 80%) and CT detected more OA lesions (100% versus 69%).
Metabolomics is an emerging field and has the potential to detect many
metabolites in a single spectrum using high resolution nuclear magnetic resonance
(NMR) techniques or mass spectrometry (MS). NMR is a reproducible and reliable non-
destructive analytical method. On the other hand, MS has a lower detection limit and is
more destructive, but it is more sensitive. NMR and MS are useful for biological fluids,
such as urine, blood plasma, serum, or synovial fluid, and have been used for metabolic
profiling in dogs, mice, sheep, and humans. Thus, many metabolites have been listed
as possibly associated to OA pathogenesis.
Pedobarographic analyses have been used to detect pressure redistribution
among limbs and within limbs in humans, equids and dogs. It has been used for
quantitative and objective assessment of lameness in dogs with unilateral elbow
dysplasia and OA, as well as for the evaluation of treatments for lameness caused by
articular pain with mavacoxib.
Scintigraphy is an imaging modality that utilizes technetium99m linked to a
diphosphonate which binds to hydroxyapatite crystals that is abundant in newly formed
bone has plenty of.
Dogs can get themselves into all kinds of trouble. Limping (known as lameness in
the veterinary world) can occur from acute trauma or from chronic disease. Ask a
VetTriage veterinarian how concerned you should be with your limping canine. In fact, a
study by Veterinary Surgery in 2020 stated that the severity of limping (termed the
“lameness score”) as depicted by video assessment in dogs with elbow disease is
useful and correlates with an in-person actual orthopedic exam.