Evaluating OA Outcomes
We have discussed the importance of early diagnosis of OA and developing a Customized CARE Plan in other sections of the CARE website. It can be easy to think our job is done after developing a thorough treatment plan. But its not. It is essential to follow up on your plan to ensure it is working or identify adverse responses to treatments.
In this article we will discuss tools you can use to track response to treatment as well as provide guidance on how quickly you should expect to see response to different therapies.
What outcome measures should I use to track response?
An outcome measure is a tool or test used to establish baseline data, then track response to treatment. Common outcome measures used to help manage canine OA include:
Bodyweight
All dogs on an OA CARE Plan should have a baseline BW established. Weight management is the single most important aspect of OA management; therefore, monitoring BW frequently is important. Dogs should be weighed on the same scale each time to minimize variation. Click here for more on weight loss.
Body condition score
All dogs on an OA CARE Plan should have a baseline BCS established. The goal BCS for a dog with OA is 4.5/9 on the 9 point scale or 2.5/5 on the 5 point scale.
Clinical Metrology Instrument (CMI)
CMIs are client questionnaires that are used to identify pain, typically by asking questions regarding function and activity. Several questionnaires have been validated for use in dogs, meaning that they have scientifically been shown to detect pain and measure response to intervention.
CARE strongly recommends adopting at least one CMI to use in your practice. Our favorite is the Client Specific Outcome Measure (CSOM). Click here to learn more about CMIs and here for a downloadable CSOM you can use in your practice.
Pain scale
Numeric pain scales that ask the client (or DVM) to rate the patient’s pain on a scale, such as 1-10, can be easily used; though they are not as good at detecting subtle pain as CMIs or questionnaires. Nevertheless, it is easy to incorporate a numeric pain scale into your evaluation and re-evaluation of patients.
We use the scale: 0= no pain; 10 = extreme/ worst pain
Lameness scale
Many veterinarians will assign a numeric score to lameness; however, there is not a universally accepted lameness scale in small animal veterinary practice. We prefer to use qualitative language that describes the dog’s gait in greater detail than numbers can provide. But, if you choose to use a lameness scale, be consistent in the descriptors for each number.
Here is the scale we prefer:
Lameness Scale
This is the scale CARE recommends for monitoring lameness| Grade | Lameness at a walk or trot |
|---|---|
| 0 | No lameness observed |
| 1 | Slight lameness |
| 2 | Obvious weight-bearing lameness |
| 3 | Severe weight-bearing lameness |
| 4 | Intermittent non weight-bearing lameness |
| 5 | Continuous non weight-bearing lameness |
Goniometry
Goniometers are used to measure joint range of motion (ROM). Rehabilitation therapists often use these to track improvement with manual and exercise therapy. These can also be used in general practice to track improvement with OA treatment.
The most commonly used goniometers are plastic and inexpensive, though app-based goniometers are also being studied. Normal goniometric measurements have been established for Labrador Retrievers (Jaegger G et al. AJVR 2002). There is a learning curve to using goniometers, but with practice, they can be an easily incorporate outcome measure for monitoring OA treatment.
However, it is crucial to note that while improving or maintaining ROM is important for managing OA, goniometry does not measure joint, limb or body function, so it should not be used as a sole outcome measure for making treatment plan adjustments.
Limb circumference
Tape measures, specifically calibrated girthometers (Guillicks), can be used to estimate muscle mass, indirectly estimate muscle strength, and measure body circumference. There is a learning curve when using these and a large amount of inter-observer variability, meaning that the same person must take the baseline and all follow-up measurements to maximize reliability.
Measurement of limb circumference is often performed by rehabilitation therapists, but it does not take the place of assessing functional outcomes. (Baker SG, et al. VCTO 2010)
Radiographs
Radiographs are a poor indicator of response to treatment. OA is expected to be a progressive disease, and radiographic progression of degenerative changes over months and years is very common.
As we know, “dogs don’t walk on their x-rays,” so we should not be making treatment adjustments based on radiographic change or lack of change. Monitoring radiographs is not typically indicated unless significant worsening of clinical symptoms occur, in which case, evaluation for neoplastic conditions must be considered.
Stance analyzer
Bathroom scales or a commercial stance analyzer can be used to measure static weight bearing. Most dogs typically distribute 60% of their body weight on the front limbs and 40% on the pelvic limbs.
One study found that there is normally about a 6% difference in weight bearing between back legs in dogs without OA. In other words, dogs can shift up to 6% of their weight to one or the other pelvic limb without being considered lame. Dogs with OA would be expected to shift weight on to less affected limbs.
Therefore, measuring static weight bearing before treatment may help diagnose lameness. Change in weight distribution following treatment could indicate that dogs are more comfortable on a limb if their weight distribution normalizes. (Hyytiainen HK et al. VCOT 2012)
Force plate, pressure mat
Force plates are scales embedded under the floor that measure the amount of force a dog places on their limbs as they walk across the plate. Pressure mats can measure similar forces as well as stride length.
These tools are useful for tracking response to treatment but are most commonly used in the research setting due to their expense, size, and other impracticalities for general practice use. It is also important to note that changes in force plate or weight bearing do not directly correlate to changes in function or pain, so these tools do not take the place of CMIs and other measures of function and pain. (Brown DC et al. JVIM 20213)
How quickly should we see improvements?
Management of OA requires a comprehensive plan that often includes NSAIDs or anti-NGF mAbs +/- adjunctive pain medications, weight loss, activity modification, exercise, environmental modifications, supplements, acupuncture, and rehabilitation techniques.
Many times more than one treatment is started at the same time, and it can be challenging to tell exactly which therapy is working. In reality, it is likely the synergy of a multi-modal approach that is expected to produce the best results. Some treatments can result in nearly immediate response, whereas others will take longer to take effect.
Here is a summary of when you should start seeing the effects of different OA treatments:
When you start seeing effects of different OA treatments
Some treatments can result in nearly immediate response, whereas others will take longer to take effect. This chart will help you know the approximate timeline to look for signs of improvement| OA Treatment | Onset of action | Notes |
|---|---|---|
| Ice | Minutes | Cryotherapy, or ice packing, achieves the quickest onset of pain relief and anti-inflammatory action. Decreased tissue temperatures are seen within a few minutes of application. 20 minutes is the recommended time of application; tissue cooling continues for up to 1 hour. See more under the Rehab section on CARE. |
| NSAIDs | Hours-Days | A clinical response to the drug should be seen within 2 weeks of starting therapy (though often some relief is seen after a single dose). Studies have shown that continued improvement should be expected week after week for at least the first 4 weeks of daily treatment, and some dogs show continued improvement for up to a year after starting an NSAID (Autefage A, Vet Rec 2011). If no improvement is seen after 4 weeks, it may be worth trying an alternative NSAID or anti-NGF mAb prior to adding a second pharmacological agent. See more in the Pain Management section of CARE. |
| Amantadine | Hours to weeks | A small pharmacokinetic study (n= 5) in healthy Greyhounds found that peak drug concentrations were reached within 1-4 hours after a single oral dose. (Norkus C, et al. 2015) A study in dogs found that following once daily dosing, significant improvement was seen after 3 weeks; these investigators did not collect results prior to 3 weeks after starting the drug. You can read more on Amantadine in the Pain Management section of CARE. |
| Gabapentin | Hours to weeks | Peak plasma levels occur about 2 hours after dosing. Oral antacids may decrease the absorption and should be separated by 2 hours. Studies have not been done looking at gabapentin for OA, thus expectations for improvement are not fully known. Sedation is common, and starting at a low dose and working up is typically recommended to potentially decrease this effect. Therefore, clinical effects in pain relief may take days to weeks if a subtherapeutic dose is initially started. You can read more about Gabapentin in the Pain Management section of CARE. |
| Adequan | Days to weeks | Following IM administration, Adequan reaches synovial tissue within 2 hours, and persists in the joint for at least 72 hours. Significant improvement has been shown after 4 weeks of treatment, but studies have not evaluated efficacy before this time point. Based on the mechanism of action, it is possible that improvement may be seen earlier than 4 weeks. It is not known how SQ administration differs in pharmacokinetics or efficacy, but clinical experience suggests that results are similar to those seen with IM administration. You can read more about Adequan in the Pain Management section of CARE. |
| Weight Loss | Weeks to months | Dogs that are overweight should lose approximately 0.5-1.5% BW per week. Therefore, depending on the amount of weight loss needed, it will take weeks to many months to achieve ideal body weight. However, decreased lameness should be expected after about 6 weeks of weight loss or about 6% BW loss and 80% improvement in lameness has been reported after 4.5 months. You can learn more about safe and effective weight loss in the Nutrition section of CARE. |
| Omega 3 Fatty Acids | 2-3 months | It takes time for omega 3 fatty acids to integrate into cell membranes, and it will take a few weeks before doses reach therapeutic levels. Therefore, clinical effects are not expected to be seen before 2 months. Clinical trials with joint diets supplemented with omega 3s have shown significant responses after 3 months of eating the test diet. You can learn more about Omega 3s in the Nutrition section. |
| Hyaluronic acid + triamcinolone | 1-4 weeks | One study showed equivalent results of HA plus steroids vs. ACP (Arthrex brand of PRP). Improvements were seen as soon as 1 week after injection and lasted at least 12 weeks You can learn more in the Pain Management section of CARE. |
| Platelet Rich Plasma | 1-3 months post injection | Three studies (with 3 different PRP products) have shown that improvement with PRP should be expected between 6-12 weeks post injection. Some dogs may begin to exhibit improvement earlier than 6 weeks, though onset of action is not expected to be within the first 1-2 weeks. You can learn more about PRP in the Pain Management section of CARE. |
| Stem Cell Therapy | 1-2 months post injection | Studies with adipose-derived autologous stem cell therapy showed clinical improvement after 30 days. Some dogs may continue to improve over subsequent months. You can learn more about Stem Cell Therapy in the Pain Management section of CARE. |
| Oral joint supplements | Months | The time to peak effect may vary depending on the type of joint supplement (glucosamine, chondroitin, GLM, UCII, etc.), but in general, expectations for improvement should not be expected before 1 month. Studies with GLM and UCII suggest effects are seen at 2 months, and continued supplementation with UCII may result in even further improvement month after month. You can learn more about joint supplements in the Nutrition section of CARE. |
| Anti-NGF mAbs | Weeks | Significant improvement compared to placebo was seen between 1 and 6 weeks after starting Librela. If no improvement is seen after the second monthly injection, it is unlikely to be seen and the diagnosis of OA should be confirmed/ other conditions such as CCLR ruled out. |
| Exercise | Days-weeks-months | The positive effects of exercise can be seen after a single workout; but optimal results come from continued exercise. Gains in strength, flexibility, and cardiovascular stamina take weeks to months to achieve. Initial gains are typically seen after 2 weeks, then further improvement is seen about every 4-6 weeks. You can learn more about good exercises and recommended duration in the Nutrition section of CARE. |
References
Jaegger G, Marcellin-Little DJ, Levine D (2002) Reliability of goniometry in Labrador Retrievers. Am J Vet Res 63(7):979–986).
Baker SG, Roush JK, Unis MD, Wodiske T. Comparison of four commercial devices to measure limb circumference in dogs VCOT 2010;23:406-410.
Hyytiäinen HK, Mölsä SH, Junnila, JT, et al. Use of bathroom scales in measuring asymmetry of hindlimb static weight bearing in dogs with osteoarthritis. VCOT 2012;25:390-396.
Brown DC, Boston RC, Farrar JT. Comparison of Force Plate Gait Analysis and Owner Assessment of Pain Using the Canine Brief Pain Inventory in Dogs with Osteoarthritis J Vet Intern Med 2013;27:22–30