Deep Arthritis Needs Controlled Energy Not More Heat

Deep-tissue targeting, wavelength-specific absorption, pulsed thermal control

A dog with arthritis can look fine for most of the day and still struggle every time it gets off the floor.

That is the frustrating part for owners and rehabilitation teams. The dog may walk into the clinic without an obvious limp, then hesitate when turning, take shorter steps after exercise, or use the front legs to pull itself upright after resting. With advanced hip or stifle disease, even a few minutes of walking can expose the problem.

The treatment challenge is not simply finding a way to “warm the joint.”

The joint may be several centimeters beneath the skin. Between the treatment head and the pathological structure are skin, subcutaneous tissue, fascia, muscle and connective tissue. Each layer changes how much optical energy continues toward the target.

This is where professional vet laser therapy becomes a treatment-engineering problem rather than a simple equipment setting.

The clinician needs enough optical energy to reach the intended tissue, but excessive continuous energy can make superficial heating the limiting factor.

For dog laser therapy for arthritis, the practical question is therefore not how much power the machine can produce.

It is how effectively the clinician can control where, when and how that energy is delivered.

The Arthritic Joint Is Deeper Than the Treatment Head

When a clinician places a laser treatment head over a dog’s stifle, hip or elbow, the optical energy begins at the skin.

The pathological tissue does not.

Photons entering biological tissue are affected by absorption and scattering.

Absorption removes energy from the optical field as tissue chromophores interact with the light.

Scattering changes photon direction and spreads the energy through a larger volume.

As a result, optical fluence decreases with depth.

The exact attenuation depends on wavelength and tissue composition.

A lean dog’s hip and a heavily muscled dog’s hip can therefore present very different treatment conditions even when the diagnosis is identical.

This is why a single generic protocol is difficult to justify for every arthritis patient.

A 6 kg dog, a 25 kg dog and a 45 kg dog do not have the same optical path.

The treatment area also matters.

A small elbow target and a large hip region require different energy-distribution strategies.

Why More Power Does Not Automatically Mean More Deep Energy

This is one of the most important points in high-intensity laser treatment.

Imagine increasing continuous power because the target is deep.

Some of that additional energy will continue deeper.

Some will also be absorbed by the tissues it encounters first.

If the superficial layers begin heating too rapidly, the operator may have to stop or reduce treatment before the desired cumulative energy reaches the deeper treatment field.

The problem is therefore not simply insufficient output.

It is the relationship between:

• Wavelength
• Tissue absorption
• Tissue scattering
• Peak power
• Average power
• Pulse frequency
• Duty cycle
• Treatment time
• Treatment area
• Handpiece movement

A modern Class IV platform is useful precisely because these variables can be managed together.

810 nm and Deeper Musculoskeletal Targets

Near-infrared wavelengths around 810 nm have an established role in photobiomodulation research because tissue scattering and absorption can provide useful conditions for deeper photon delivery.

The wavelength does not pass through tissue without attenuation.

It still loses energy.

But compared with wavelengths that are strongly absorbed or scattered near the surface, the 810 nm region can provide a useful option for deeper musculoskeletal treatment.

That makes it relevant when the clinician is working around:

• Hip joints
• Stifle joints
• Elbows
• Large muscle groups
• Periarticular tissue

FotonMedix’s VetMedix-Max platform includes 650, 810, 915, 940 and 980 nm wavelengths and provides continuous, pulse and super-pulse operating modes, with a stated peak output of up to 38 W.

The important clinical feature is the combination of spectral and temporal control.

The system does not force the clinician to use one wavelength or one emission pattern for every anatomical target.

980 nm Changes the Thermal Profile

Moving toward 980 nm changes tissue interaction.

Water absorption becomes more significant, so a larger proportion of the optical energy can contribute to local thermal effects.

This is not automatically undesirable.

Controlled temperature elevation can be part of the intended treatment response.

The problem is uncontrolled accumulation.

A large arthritic joint may require substantial energy because the target is deep. At the same time, superficial tissue may absorb enough energy to become uncomfortable before the treatment has reached its intended endpoint.

That creates the central contradiction in high-intensity dog laser therapy for arthritis.

The clinician wants enough energy to matter.

The clinician does not want surface heat to determine when the session has to stop.

This is why thermal control is not an optional technical detail.

It is part of the treatment strategy.

Duty Cycle Controls More Than Pulse Timing

Duty cycle describes the proportion of a pulse period during which the laser is actively emitting.

This creates a difference between peak output and average exposure.

A high peak output can be delivered for a shorter portion of the cycle, followed by an off period.

During the active period, the tissue receives concentrated optical energy.

During the off period, heat continues to diffuse and blood flow can contribute to thermal redistribution.

The result can be a different thermal profile from continuous operation at the same peak output.

This does not mean that pulsed operation makes excessive energy harmless.

It does not.

The total energy, tissue characteristics, treatment area and patient response still matter.

But duty cycle gives the clinician another way to manage the relationship between intensity and heat.

For a deep canine joint, that flexibility can be valuable.

980 nm and Hemoglobin Require a More Careful Explanation

The interaction between 980 nm and tissue is sometimes simplified into a statement about hemoglobin.

The actual picture is more complicated.

Hemoglobin has wavelength-dependent absorption characteristics, and oxygenation affects its optical behavior.

Water is also an important absorber.

Blood volume, vascularity and tissue perfusion therefore influence how optical energy behaves inside biological tissue.

At 980 nm, water absorption becomes increasingly relevant, while vascular tissue can contribute to energy absorption and thermal transport.

This matters because tissue is not an optical vacuum.

The laser interacts with a living, perfused structure.

Blood flow can help redistribute heat.

At the same time, highly vascular tissue can change local absorption.

For clinicians using high-intensity laser treatment, this is another reason to think in terms of controlled energy deposition rather than assuming that a wavelength has one isolated biological effect.

Why 1470 nm Belongs to a Different Clinical Conversation

1470 nm provides a useful comparison because water absorbs this wavelength much more strongly than it absorbs many lower near-infrared wavelengths.

The consequence is stronger and more localized photothermal interaction.

That characteristic can be extremely useful for surgery.

FotonMedix’s SurgMedix platform uses 1470 nm and 980 nm configurations for surgical applications where controlled tissue cutting, coagulation and ablation are required.

That does not mean 1470 nm should automatically be selected for non-invasive canine arthritis rehabilitation.

The treatment objectives are different.

A surgeon performing controlled tissue ablation wants concentrated absorption.

A rehabilitation clinician treating a dog’s arthritic hip usually wants controlled energy delivery through a broader tissue volume without creating excessive superficial thermal accumulation.

Wavelength selection should therefore follow the clinical target.

Not the marketing appeal of the highest absorption number.

A Simulated Canine Arthritis Case

The following is a simulated veterinary rehabilitation case for clinical education and treatment-planning illustration. It is not a published patient record, and the numerical parameters are not a universal prescription.

Case Identification

A 9-year-old female spayed Labrador Retriever weighing 33.8 kg is referred for chronic right stifle pain.

The owner reports that the dog has become slower when getting up after sleeping and has stopped voluntarily climbing into the car.

The dog still enjoys walking but begins shortening the right hind-limb stride after approximately 10 minutes.

Radiographs demonstrate moderate-to-severe degenerative changes in the right stifle.

The rehabilitation department assigns a Grade III osteoarthritis classification for internal clinical documentation.

The dog is already receiving veterinarian-managed multimodal pain care.

High-intensity laser therapy is introduced as an adjunct to rehabilitation.

Simulated Treatment Record

Parameter	Clinical Record
Department	Small Animal Rehabilitation
Simulated Case Number	SAR-DLA-2026-071
Species	Canine
Breed	Labrador Retriever
Age	9 years
Sex	Female, spayed
Body Weight	33.8 kg
Primary Diagnosis	Right stifle osteoarthritis
Pathological Grade	Grade III
Primary Functional Problem	Pain after rest and reduced walking tolerance
Laser Class	High-intensity Class IV
Wavelengths	810 nm + 915 nm + 940 nm + 980 nm
Initial Peak Power	22 W
Final Peak Power	30 W
Frequency	15 Hz
Initial Duty Cycle	40%
Final Duty Cycle	45%
Session 1 Energy	800 J
Session 3 Energy	1,000 J
Session 6 Energy	1,300 J
Treatment Frequency	2 sessions weekly
Initial Treatment Course	3 weeks
Treatment Area	Stifle and surrounding periarticular musculature
Monitoring	Patient behavior, surface thermal response and functional change
Concurrent Rehabilitation	Controlled walking and strengthening

The treatment does not begin at maximum output.

That is deliberate.

The first appointment provides information about patient tolerance, tissue response and practical treatment time.

A high-intensity system is most useful when the clinician can increase treatment intensity when clinically appropriate rather than starting every patient at the upper limit.

Session 1 Establishes the Baseline

The dog enters the rehabilitation room with a stiff gait.

The right hind limb is visibly less active during turns.

The clinician begins with 22 W peak output, 15 Hz and a 40% duty cycle.

The handpiece is moved continuously over the stifle region and surrounding soft tissue.

The treatment is not concentrated on a single point.

This matters because the objective is to distribute energy across the intended treatment field.

Total delivered energy reaches approximately 800 J.

The dog remains calm.

No excessive thermal response is observed.

Immediately after treatment, the dog still has an abnormal gait.

That is not surprising.

The first session is not judged by whether the dog suddenly becomes normal.

The team establishes a baseline against which later functional changes can be compared.

Week 1 Reveals the First Functional Change

Two sessions are completed during the first week.

The owner reports that the dog gets up somewhat faster after resting.

The dog still avoids jumping into the car.

Walking tolerance increases from approximately 10 minutes to 14 minutes in the simulated record.

Pain interference changes from 7/10 to 6/10.

The treatment energy is increased modestly.

No major change is made to every variable simultaneously.

This is an important clinical habit.

If power, frequency, duty cycle and exposure time all change together, it becomes difficult to determine why the patient responded differently.

Controlled progression produces cleaner clinical information.

Session 3

At the third session, the treatment energy increases to approximately 1,000 J.

Peak output is increased to 24 W.

Frequency remains at 15 Hz.

Duty cycle remains at 40%.

The clinician expands the treatment field slightly into the quadriceps and periarticular musculature because the dog’s movement pattern suggests secondary muscle guarding.

This is a useful distinction.

The radiograph identifies the arthritic joint.

The dog’s movement pattern identifies the broader treatment problem.

Session 6

By the sixth session, the simulated treatment reaches 1,300 J.

Peak output is increased to 30 W.

Duty cycle increases to 45%.

The dog now walks for approximately 25 minutes before showing obvious stride shortening.

The owner reports that the dog is more willing to approach the car.

The simulated pain interference score falls from 7/10 to 4/10.

The treatment is not continued upward simply because the equipment can produce more energy.

The treatment objective is functional improvement.

If the patient is improving and tolerating the protocol, there is no clinical logic in chasing maximum output for its own sake.

Simulated Outcome Data

Clinical Measure	Baseline	Week 1	Week 3
Pain interference	7/10	6/10	4/10
Walking tolerance	10 min	14 min	25 min
Rising after rest	Markedly slow	Moderately slow	Mildly slow
Car entry	Refuses	Needs assistance	Voluntary attempt
Hind-limb stride	Clearly shortened	Moderately shortened	Mildly shortened
Owner activity score	4/10	5/10	7/10
Session energy	800 J	1,000 J	1,300 J
Peak power	22 W	24 W	30 W
Duty cycle	40%	40%	45%
Frequency	15 Hz	15 Hz	15 Hz

These values illustrate a simulated treatment progression and should not be interpreted as expected outcomes for every arthritis patient.

Why the Treatment Field Includes More Than the Joint

An arthritic stifle does not operate independently from the surrounding muscles.

Pain changes movement.

Changed movement changes muscle loading.

Muscle guarding can alter the way the dog stabilizes the joint.

A dog protecting one limb may also change pelvic movement and spinal mechanics.

That means a treatment plan based exclusively on placing the laser directly over the joint may miss part of the functional problem.

The clinician may therefore treat:

• The joint line
• Periarticular tissue
• Quadriceps
• Hamstrings
• Surrounding connective tissue

The exact treatment field depends on diagnosis and clinical assessment.

The important point is that laser treatment should follow anatomy and function rather than simply following an X-ray.

What Published Veterinary Research Adds to the Discussion

The evidence for canine laser therapy has developed beyond anecdotal reports, although it remains heterogeneous.

A randomized, double-blinded controlled study published in 2022 evaluated 20 dogs and 40 osteoarthritic joints and compared a three-week Class IV photobiomodulation protocol with meloxicam treatment.

The investigators assessed pain, gait, stiffness, function and quality-of-life-related outcomes.

Several outcomes showed improvement at selected follow-up points.

Another study involving 23 dogs with naturally occurring osteoarthritis used accelerometers to evaluate activity during a six-week treatment period. The researchers reported increases in daily activity and step counts during treatment.

These studies are relevant because they evaluate what owners and veterinarians actually care about.

Movement.

Activity.

Pain-related behavior.

Function.

They also demonstrate why treatment evidence should not be reduced to a single claim such as “laser decreases inflammation.”

The clinical question is broader.

Does the treatment help the patient move more comfortably?

Can the patient participate more effectively in rehabilitation?

Does the improvement persist?

Can the treatment be tolerated repeatedly?

Why Evidence Does Not Support One Universal Protocol

Veterinary laser studies use different:

• Wavelengths
• Treatment energies
• Frequencies
• Duty cycles
• Treatment schedules
• Outcome measures
• Disease severities

A systematic review of laser therapy in veterinary medicine has also identified substantial variation in treatment parameters and limitations in the evidence quality across indications.

That means a protocol should not be copied blindly from one study into every veterinary hospital.

The published study provides evidence about a specific treatment condition.

The clinician still has to account for the actual patient.

A 40 kg dog with deep hip disease is not equivalent to a 5 kg dog with superficial elbow pain.

Clinical evidence provides the framework.

Patient assessment determines how the framework is applied.

Why Peak Power Should Never Be the Only Specification Buyers Compare

A veterinary hospital evaluating Class IV equipment may see 20 W, 30 W, 38 W or higher output ratings.

It is tempting to compare these numbers directly.

That can be misleading.

A machine with higher peak power does not automatically produce better clinical outcomes.

The buyer should also examine whether the platform provides:

Multi-Wavelength Control

Different wavelengths interact differently with tissue.

Pulse Modes

Pulsed delivery can alter the temporal energy profile.

Duty Cycle Adjustment

The active emission percentage affects average exposure and thermal accumulation.

Treatment Control

The clinician needs to manage energy distribution across the treatment field.

Thermal Management

Patient comfort should remain observable throughout the treatment.

Repeatability

A professional department needs to reproduce and document treatment settings.

This is why a B2B equipment evaluation should focus on the complete energy-delivery architecture.

The Practical Role of 650 nm

Not every veterinary treatment target is deep.

A superficial soft-tissue problem, wound-related application or shallow anatomical structure presents a different optical problem from a canine hip.

The 650 nm region interacts with tissue differently from the deeper near-infrared wavelengths.

That makes it useful as part of a multi-wavelength platform rather than as a universal setting.

VetMedix-Max’s combination of 650, 810, 915, 940 and 980 nm gives the veterinary team a broader spectral range.

The clinical benefit is flexibility.

The clinician can consider tissue depth and absorption rather than treating wavelength as an arbitrary machine preset.

Why 1470 nm Is More Relevant to Surgical Laser Applications

The 1470 nm wavelength is particularly interesting because water absorbs it strongly.

That creates rapid energy deposition within water-rich tissue.

In a surgical environment, this can support precise tissue interaction.

FotonMedix’s SurgMedix 1470 nm and 980 nm platform is designed around this type of surgical application.

That is different from non-invasive rehabilitation.

For arthritis, the clinician generally does not want highly localized water absorption to dominate the treatment volume.

The objective is controlled energy delivery through a broader region.

This is why a surgical wavelength configuration should not simply be copied into a rehabilitation protocol.

Different clinical objectives require different optical strategies.

Thermal Control Is Part of Treatment Quality

A treatment that becomes too hot is not merely uncomfortable.

It can alter the entire session.

The operator may have to reduce output.

The treatment may have to stop early.

The patient may become resistant to future sessions.

The owner may lose confidence.

For dogs, behavioral feedback can be surprisingly useful.

A dog that suddenly turns toward the handpiece, moves away, becomes restless or repeatedly changes position may be signaling excessive warmth or discomfort.

Surface temperature measurement can provide another objective indicator.

The clinician should consider both.

Temperature is data.

Behavior is also data.

Neither should be ignored.

Why Continuous Movement Matters

A stationary treatment head concentrates energy in one region.

A moving handpiece distributes energy across the intended field.

This influences both dose distribution and thermal accumulation.

For a large dog’s stifle, hip or shoulder, continuous movement allows the clinician to cover the broader periarticular area while reducing the chance that one small region receives disproportionate exposure.

The exact movement pattern should be determined by the treatment objective and device instructions.

But the basic principle is straightforward:

High-intensity treatment should be controlled spatially as well as temporally.

The Real Meaning of Deep-Tissue Treatment

“Deep penetration” is often used too casually.

A clinician should not assume that a wavelength reaches a particular depth with unchanged intensity.

It does not.

The optical energy decreases continuously through tissue.

The relevant question is whether sufficient energy remains within the target volume to produce the intended interaction.

That depends on:

• Wavelength
• Absorption
• Scattering
• Tissue thickness
• Tissue composition
• Treatment geometry
• Output
• Exposure time

This is why optical penetration claims should always be interpreted as relative tissue behavior rather than as a guarantee that a certain percentage of energy reaches an exact anatomical depth.

Why Dog Arthritis Treatment Is a Long-Term Service

Canine osteoarthritis is usually a chronic condition.

The dog does not become a non-arthritic dog after six treatments.

The structural disease remains.

That changes how a veterinary hospital should think about dog laser therapy for arthritis.

The goal is not a single dramatic intervention.

The goal is a sustainable rehabilitation pathway.

A clinic can combine laser sessions with:

• Exercise therapy
• Weight management
• Mobility assessment
• Strengthening
• Home exercise
• Veterinary pain management
• Environmental modifications

Laser treatment can be scheduled as part of this larger program.

This approach also creates better opportunities for follow-up.

The clinic can monitor whether the dog’s walking tolerance changes.

The owner can report stair use.

The rehabilitation therapist can evaluate gait.

The veterinarian can reassess pain.

The treatment then becomes measurable.

What Owners Actually Want From Dog Laser Therapy

Owners rarely ask how the optical attenuation coefficient changes with wavelength.

They ask whether their dog can walk again without struggling.

They want to know whether the dog can get into the car.

They want to know whether the dog can sleep comfortably.

They want to know whether their aging Labrador can go around the block.

Those are the outcomes that should guide the clinical conversation.

The laser treatment record may contain 1,300 J.

The owner should hear that the dog’s walking tolerance increased from 10 minutes to 25 minutes in a simulated example.

The machine produces energy.

The clinical team measures function.

That distinction makes the treatment easier to understand and easier to evaluate.

How Vet Laser Therapy Fits Into a Veterinary Hospital

A professional vet laser therapy program can support several departments.

Rehabilitation

Chronic arthritis, postoperative recovery and mobility programs.

Orthopedics

Adjunctive treatment around painful joints and soft tissues.

Sports Medicine

Muscle and tendon rehabilitation in active dogs.

Senior Pet Care

Mobility and comfort programs for aging animals.

Wound Management

Appropriate laser protocols may be incorporated into selected wound-care workflows.

Pain Management

Laser treatment can become one physical modality within a broader multimodal plan.

The machine therefore does not have to remain confined to one diagnosis.

Its value comes from how many appropriate clinical workflows it can support.

A More Realistic Way to Compare Laser With Conventional Treatment

It is not clinically useful to say that laser treatment “replaces” medication.

Medication and laser therapy work through different mechanisms.

Weight management changes mechanical loading.

Exercise changes muscle function.

Surgery addresses structural pathology when indicated.

Laser therapy provides a non-invasive physical treatment modality.

The better question is whether laser can complement existing care.

For a dog with arthritis, that may mean improved comfort during rehabilitation.

A more comfortable dog may participate better in controlled exercise.

Better exercise participation can help maintain muscle strength.

Maintaining muscle can support functional mobility.

That is a more realistic clinical pathway than claiming that laser alone reverses degenerative joint disease.

Why a Multi-Wavelength Class IV Platform Is More Flexible

A veterinary practice sees different animals every day.

One dog may have a deep hip problem.

Another may have a superficial wound.

Another may need postoperative rehabilitation.

A cat may have elbow osteoarthritis.

A sporting dog may have muscular overuse.

These conditions do not present the same optical target.

A multi-wavelength platform provides more options for matching treatment parameters to tissue characteristics.

VetMedix-Max combines five wavelengths with high-intensity output and multiple emission modes.

That gives the clinician greater control over the treatment envelope.

It does not remove the need for clinical judgment.

It makes clinical judgment more useful.

The Treatment Protocol Should Be Adjustable

A rigid protocol may look convenient on paper.

Real patients are not rigid.

The clinician may discover that a dog heats quickly at one setting.

Another dog may tolerate the same setting comfortably.

One patient may show rapid functional improvement.

Another may need a longer course.

One treatment field may be small.

Another may involve a large muscular region.

A professional protocol should therefore record the starting parameters and define why adjustments are made.

This makes treatment more reproducible.

It also gives the veterinary team a better basis for evaluating outcomes.

What a Proper Laser Treatment Record Should Contain

A professional treatment record can include:

Patient Information

Age, sex, breed, body weight and diagnosis.

Pathology

Disease grade and affected anatomical structure.

Wavelength

Every wavelength used during the session.

Peak Power

The maximum instantaneous output.

Frequency

Pulse frequency where applicable.

Duty Cycle

The percentage of active emission.

Total Energy

Delivered joules.

Treatment Area

Anatomical region and approximate field.

Session Duration

Actual exposure time.

Thermal Response

Observed patient response and temperature information where available.

Functional Outcome

Pain, gait, activity or another measurable endpoint.

This creates a clinical record that is much more valuable than simply writing “laser treatment completed.”

The B2B Purchasing Question Is Bigger Than Wattage

For an international veterinary equipment buyer, the machine needs to work in real clinical conditions.

The hospital needs reliable operation.

The clinician needs adjustable treatment parameters.

The rehabilitation team needs repeatable protocols.

The business needs enough versatility to serve different patient types.

The equipment should therefore be evaluated through practical questions.

Can it support deep musculoskeletal applications?

Can the operator change wavelength?

Can peak output be controlled?

Can pulse modes be selected?

Can duty cycle be adjusted?

Can the treatment be documented?

Can the same platform support different veterinary departments?

A high-intensity system becomes commercially useful when the answer to these questions fits the hospital’s workflow.

Final Clinical Perspective

The strongest argument for dog laser therapy for arthritis is not that the laser is powerful.

It is that high-intensity energy can be controlled.

An arthritic joint is surrounded by living tissue.

Optical energy attenuates as it travels through those layers.

Different wavelengths change the balance between scattering and absorption.

810 nm can provide useful near-infrared characteristics for deeper musculoskeletal treatment.

980 nm creates stronger interaction with water and therefore requires closer attention to thermal management.

1470 nm has substantially stronger water absorption and illustrates why it is particularly relevant to localized surgical applications rather than being automatically transferred into non-invasive arthritis protocols.

Pulse frequency changes the timing of energy delivery.

Duty cycle changes the relationship between peak output and average exposure.

Handpiece movement changes spatial distribution.

Patient monitoring tells the clinician whether the treatment remains tolerable.

That is what professional vet laser therapy should look like.

It should not be a race toward maximum power.

It should be a controlled process built around the anatomy and functional needs of the patient.

For a dog with chronic arthritis, that means enough energy to address a deep target without allowing surface heat to become the reason treatment has to stop.

It also means recognizing what laser therapy cannot do.

It cannot erase radiographic osteoarthritis.

It cannot replace diagnosis.

It cannot replace appropriate analgesia.

It cannot replace exercise.

It cannot replace weight management.

It cannot replace surgery when surgery is indicated.

What it can provide is another non-invasive physical treatment option within a multimodal veterinary rehabilitation program.

That difference matters.

Traditional veterinary care gives clinicians established tools for controlling pain, reducing mechanical stress, improving strength and addressing structural disease.

High-intensity laser adds another controllable layer.

When wavelength, power, pulse structure, duty cycle and treatment area are selected deliberately, the clinician has more control over the balance between deep energy delivery and superficial thermal exposure.

For the owner, the result is not a specification sheet.

It is a dog that may rise more easily, walk farther or participate more willingly in rehabilitation.

For the veterinary hospital, the result is not simply another piece of equipment.

It can become a structured treatment service with documented parameters, measurable outcomes and repeatable clinical workflows.

That is the practical value of modern Class IV vet laser therapy.

Not maximum heat.

Not maximum power.

Controlled energy directed toward a meaningful clinical goal.