Diagnosis is made with reasonable certainty based on history and clinical examination. X-rays may confirm the diagnosis. The typical changes seen on X-ray include: joint space narrowing, subchondral sclerosis (increased bone formation around the joint), subchondral cyst formation, and osteophytes. Plain films may not correlate with the findings on physical examination or with the degree of pain. Usually other imaging techniques are not necessary to clinically diagnose osteoarthritis.

In 1990, the American College of Rheumatology, using data from a multi-center study, developed a set of criteria for the diagnosis of hand osteoarthritis based on hard tissue enlargement and swelling of certain joints. These criteria were found to be 92% sensitive and 98% specific for hand osteoarthritis versus other entities such as rheumatoid arthritis and spondyloarthropathies.

Related pathologies whose names may be confused with osteoarthritis include pseudo-arthrosis. This is derived from the Greek roots "pseudo-", meaning "false", and "arthr-", meaning "joint", together with the ending "-osis" used for disorders. Radiographic diagnosis results in diagnosis of a fracture within a joint, which is not to be confused with osteoarthritis which is a degenerative pathology affecting a high incidence of distal phalangeal joints of female patients. A polished ivory-like appearance may also develop on the bones of the affected joints, reflecting a change called eburnation.

A number of classification systems are used for gradation of osteoarthritis:

- WOMAC scale, taking into account pain, stiffness and functional limitation.

- Kellgren-Lawrence grading scale for osteoarthritis of the knee. It uses only projectional radiography features.

- Tönnis classification for osteoarthritis of the hip joint, also using only projectional radiography features.

Osteoarthritis can be classified into either primary or secondary depending on whether or not there is an identifiable underlying cause.

Both primary generalized nodal osteoarthritis and erosive osteoarthritis (EOA, also called inflammatory osteoarthritis) are sub-sets of primary osteoarthritis. EOA is a much less common, and more aggressive inflammatory form of osteoarthritis which often affects the distal interphalangeal joints of the hand and has characteristic articular erosive changes on x-ray.

Osteoarthritis can be classified by the joint affected:

- Hand:

- Trapeziometacarpal osteoarthritis

- Wrist (wrist osteoarthritis)

- Vertebral column (spondylosis)

- Facet joint arthrosis

- Hip osteoarthritis

- Knee osteoarthritis

The classic diagnostic technique is with appropriate X-rays and hip scoring tests. These should be done at an appropriate age, and perhaps repeated at adulthood - if done too young they will not show anything. Since the condition is to a large degree inherited, the hip scores of parents should be professionally checked before buying a pup, and the hip scores of dogs should be checked before relying upon them for breeding. Despite the fact that the condition is inherited, it can occasionally arise even to animals with impeccably hip scored parents.

In diagnosing suspected dysplasia, the x-ray to evaluate the internal state of the joints is usually combined with a study of the animal and how it moves, to confirm whether its quality of life is being affected. Evidence of lameness or abnormal hip or spine use, difficulty or reduced movement when running or navigating steps, are all evidence of a problem. Both aspects have to be taken into account since there can be serious pain with little X-ray evidence.

It is also common to X-ray the spine and legs, as well as the hips, where dysplasia is suspected, since soft tissues can be affected by the extra strain of a dysplastic hip, or there may be other undetected factors such as neurological issues (e.g. nerve damage) involved.

There are several standardized systems for categorising dysplasia, set out by respective reputable bodies (Orthopedic Foundation for Animals/OFA, PennHIP, British Veterinary Association/BVA). Some of these tests require manipulation of the hip joint into standard positions, in order to reveal their condition on an X-ray.

The following conditions can give symptoms very similar to hip dysplasia, and should be ruled out during diagnosis:

- Cauda equina syndrome (i.e. lower back problems)

- Cranial (anterior) cruciate ligament tears

- Other rear limb arthritic conditions

- Osteochondritis dissecans and elbow dysplasia in the forelimbs are difficult to diagnose as the animal may only exhibit an unusual gait, and may be masked by, or misdiagnosed as, hip dysplasia.

A dog may misuse its rear legs, or adapt its gait, to compensate for pain in the "forelimbs", notably osteoarthritis, osteochondritis (OCD) or shoulder or elbow dysplasia, as well as pain in the hocks and stifles or spinal issues. It is important to rule out other joint and bodily issues before concluding that only hip dysplasia is present. Even if some hip dysplasia is present, it is possible for other conditions to co-exist or be masked by it.

Two elements are considered: radiology and joint fluid analysis.

Radiology has a large role to play in finding chondrocalcinosis, with radiographs, CT scans, MRIs, US, and nuclear medicine all having a part. CT scans and MRIs show calcific masses (usually within the ligamentum flavum or joint capsule), however radiography is more successful. At ultrasound, chondrocalcinosis may be depicted as echogenic foci with no acoustic shadow within the hyaline cartilage. As with most conditions, CPPD can present with similarity to other diseases such as ankylosing spondylitis and gout.

Arthrocentesis, or removing synovial fluid from the affected joint, is performed to test the synovial fluid for the calcium pyrophosphate crystals that are present in CPPD. When stained with H&E stain, calcium pyrophosphate crystals appears deeply blue ("basophilic"). However, CPP crystals are much better known for their rhomboid shape and weak positive birefringence on polarized light microscopy, and this method remains the most reliable method of identifying the crystals under the microscope. However, even this method suffers from poor sensitivity, specificity, and inter-operator agreement.

These two modalities currently define CPPD disease but lack diagnostic accuracy, and are potentially epiphenomenological.

Facet syndrome can typically be diagnosed through a physical examination, MRI, x-rays and/or a diagnostic block into the suspected joint.

Facet syndrome has no specific code in ICD-10. It can be diagnosed as “other” in M53.8 – other specified dorsopathies.

Diagnosis is simple; usually a doctor can diagnose shoulder arthritis by symptoms, but they may ask for an x-ray or MRI for confirmation.

Diagnosis is made by clinical examination from an appropriate health professional, and may be supported by other tests such as radiology and blood tests, depending on the type of suspected arthritis. All arthritides potentially feature pain. Pain patterns may differ depending on the arthritides and the location. Rheumatoid arthritis is generally worse in the morning and associated with stiffness; in the early stages, patients often have no symptoms after a morning shower. Osteoarthritis, on the other hand, tends to be worse after exercise. In the aged and children, pain might not be the main presenting feature; the aged patient simply moves less, the infantile patient refuses to use the affected limb.

Elements of the history of the disorder guide diagnosis. Important features are speed and time of onset, pattern of joint involvement, symmetry of symptoms, early morning stiffness, tenderness, gelling or locking with inactivity, aggravating and relieving factors, and other systemic symptoms. Physical examination may confirm the diagnosis, or may indicate systemic disease. Radiographs are often used to follow progression or help assess severity.

Blood tests and X-rays of the affected joints often are performed to make the diagnosis. Screening blood tests are indicated if certain arthritides are suspected. These might include: rheumatoid factor, antinuclear factor (ANF), extractable nuclear antigen, and specific antibodies.

Wobblers is definitively diagnosed by x-ray, nuclear scintography or bone scan. X-rays will show channel widening or filling the easiest and are often most cost effective to horse owners. X-rays will also show any structural anomaly, arthritis, facet remodeling, or bone spurs present. Preliminary diagnosis can be made by ultrasound but x-rays are needed to measure the true depth of facet involvement. For extent of damage to associated structures, veterinarians may opt to have the horse undergo a bone scan or nuclear scintography.

Chondrocalcinosis can be visualized on projectional radiography, CT scan, MRI, US, and nuclear medicine. CT scans and MRIs show calcific masses (usually within the ligamentum flavum or joint capsule), however radiography is more successful. At ultrasound, chondrocalcinosis may be depicted as echogenic foci with no acoustic shadow within the hyaline cartilage. As with most conditions, chondrocalcinosis can present with similarity to other diseases such as ankylosing spondylitis and gout.

Osteoarthritis between the radius bone and the carpals is indicated by a "radiocarpal joint space" of less than 2mm.

X-rays can be very helpful in diagnosing and differentiating between SNAC and SLAC wrists. On the other hand, X-rays are not always sufficient to distinguish between different stages. It is important to note that both hands need to be compared. Therefore, two X-rays are needed: one from the left and one from the right hand. When the X-ray is inconclusive, wrist arthroscopy can be performed.

SLAC

Because the scapholunate ligament is ruptured, the scaphoid and lunate are not longer connected. This results in a larger space between the two bones, also known as the Terry Thomas sign. A space larger than 3 mm is suspicious and a space larger than 5 mm is a proven SLAC pathology. Scaphoid instability due to the ligament rupture can be stactic or dynamic. When the X-ray is diagnostic and there is a convincing Terry Thomas sign it is a static scaphoid instability. When the scaphoid is made unstable by either the patient or by manipulation by the examining physician it is a dynamic instability.

In order to diagnose a SLAC wrist you need a posterior anterior (PA) view X-ray, a lateral view X-ray and a fist view X-ray. The fist X-ray is often made if there is no convincing Terry Thomas sign. A fist X-ray of a scapholunate ligament rupture will show a descending capitate. Making a fist will give pressure at the capitate, which will descend if there is a rupture in the scapholunate ligament.

SNAC

In order to diagnose a SNAC wrist you need a PA view X-ray and a lateral view X-ray. As in SLAC, the lateral view X-ray is performed to see if there is a DISI.

Computed tomography (CT) or Magnetic Resonance Imaging (MRI) are rarely used to diagnose SNAC or SLAC wrist osteoarthritis because there is no additional value. Also, these techniques are much more expensive than a standard X-ray. CT or MRI may be used if there is a strong suspicion for another underlying pathology or disease.

Examination will often show tenderness at the radioscaphoid joint (when palpated or while moving the radioscaphoid joint), dorsal radial swelling and instability of the wrist joint. Notice that people may say they have trouble with rising from a chair when pressure is exerted on the hands by pushing against the handrail. Younger people may complain about not being able to do push-ups anymore because of a painful hand.

There are a number of tests and actions that can be performed when a patient is suspected of having osteoarthritis caused by SLAC or SNAC.

SLAC:

- Tenderness 1 cm above Lister’s Tubercle

Tests:

- Watson's test

- Finger extension test

SNAC:

- Tenderness at the anatomical snuff box

- Painful pronation and supination when performed against resistance

- Pain during axial pressure

When faced with monoarthritis, one of the main decisions to make is whether to perform a "joint aspirate" by inserting a needle into the affected joint and removing some fluid for microscopic analysis. This decision is largely taken on inflammatory markers in blood tests (e.g. CRP), fever and the clinical picture. The main use of aspiration is to detect bacteria and neutrophil granulocytes (in septic arthritis) and crystals (crystal arthropathies).

Depending on the level of pain and damage suffered by a patient, a physician will recommend a treatment regimen that will relieve symptoms. Some of the most common recommendations include avoiding activities that make the pain worse, ice the knee for 20 to 30 minutes throughout the day to reduce inflammation, use over the counter anti-inflammatory medications, paracetamol (acetaminophen) and physical therapy.

Topical creams and patches can also be used for pain treatment and they have been proven to reduce pain by 33 to 57%.

Exercises can help increase range of motion and flexibility as well as help strengthen the muscles in the leg. Physical therapy and exercise are often effective in reducing pain and improving function. Working with a physical therapist to find exercises that promote function without risking further injury is effective for most patients. Many of the exercises used can be performed while sitting in a chair or standing in place. They are performed so that additional stress or weight is not placed on the knee joint. Water exercises are highly recommended along with the use of elastic bands.

Supportive devices like knee braces can be used. In most cases, the arthritis is centered on a single side of the knee, so braces are effective in providing stability to one side. Two different forms of braces are available. A support brace provides the aid the entire knee requires, where an up-loader brace shifts the pressure away from the specific part of the knee that is experiencing the pain. Shoes or inserts that are considered to be energy absorbing are found useful for some patients as well as walking devices like a cane. Shoe insoles that are fitted to correct flat feet have provided relief to many patients.

The use of oral steroids and anti-inflammatory medicines help to reduce the amount of inflammation and pain felt in the knee. If over the counter medicines like ibuprofen or naproxen are not strong enough, prescription strength medicines are used. If oral medicine and physical therapy don't help your knee enough, doctors may consider giving patients injections with pain medicine. Hyaluronic acid is present in the knee, but injections of it can be used to protect the joint when the cartilage becomes thinner and can't do it alone. These injections can provide more pain relief than oral medications lasting from six months to a year.

Surgery is the final option but may be required to relieve symptoms. Arthroscopy is performed through tiny cuts where damaged parts of the knee can be removed. Osteotomy is performed to reshape the bones in the knee and is only performed if one side of the knee is damaged. Arthroplasty is a replacement surgery where an artificial joint is used.

Low level laser therapy can be considered for relief of pain and stiffness associated with osteoarthritis.

In general, anti-inflammatory drugs are prescribed initially. This medical treatment is usually accompanied by physiotherapy to increase back and stomach muscles. Thus, the spine can be both relieved and stabilized. If these conservative measures do not bring about betterment, minimally invasive procedures such as a facet infiltration can be conducted to offer relief. In this procedure, a local anesthetic is injected directly into the respective joint, usually in combination with a cortisone preparation (corticosteroid).

Because any medication that could reduce the inflammation of CPPD bears a risk of causing organ damage, treatment is not advised if the condition is not causing pain.

For acute pseudogout, treatments include intra-articular corticosteroid injection, systemic corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs), or, on occasion, high-dose colchicine. In general, NSAIDs are administered in low doses to help prevent CPPD. However, if an acute attack is already occurring, higher doses are administered. If nothing else works, hydroxychloroquine or methotrexate may provide relief.

Research into surgical removal of calcifications is underway, however this still remains an experimental procedure.

Diagnosis is through x-rays, arthroscopy or CT (computed tomography). In cases with significant lameness, surgery is the best option, especially with UAP. However, conservative treatment is often enough for cases of FMCP and OCD of the medial humeral epicondyle. The dogs are exercised regularly and given pain medication, and between the ages of 12 to 18 months the lameness will often improve or disappear. Control of body weight is important in all cases of elbow dysplasia, and prevention of quick growth spurts in puppies may help to prevent the disease.

Surgery for FMCP consists of removal of cartilage and bone fragments and correction of any incongruity of the joint. Reattachment of UAP with a screw is usually attempted before the age of 24 weeks, and after that age the typical treatment is removal of the UAP. Without surgery, UAP rapidly progresses to osteoarthritis, but with FMCP osteoarthritis typically occurs with or without surgery. Osteoarthritis is also a common sequela of OCD of the humerus despite medical or surgical treatment. Elbow replacement surgery has been developed and can be an option for treatment

There is no known cure for either rheumatoid or osteoarthritis. Treatment options vary depending on the type of arthritis and include physical therapy, lifestyle changes (including exercise and weight control), orthopedic bracing, and medications. Joint replacement surgery may be required in eroding forms of arthritis. Medications can help reduce inflammation in the joint which decreases pain. Moreover, by decreasing inflammation, the joint damage may be slowed.

No non-invasive tests are currently able to diagnose articular cartilage damage. Additionally, symptoms vary considerably from person to person. Or as Dr. Karen Hambly stated:

MRI-scans are becoming more valuable in the analysis of articular cartilage but their use is still expensive and time consuming. X-rays show only bone injuries and are therefore not very helpful in diagnosing cartilage damage, especially not in early stages. The best tool for diagnosing articular damage is the use of arthroscopy.

About 25% of people over the age of 50 experience knee pain from degenerative knee diseases.

Treatment of shoulder arthritis is usually aimed at reducing pain; there is no way to replace lost cartilage except through surgery. Pain medicines available over-the-counter can be prescribed by the doctor, but another form of treatment is cryotherapy, which is the use of cold compression. Some vitamin supplements have been found to prevent further deterioration; glucosamine sulfate is an effective preserver of cartilage. Another way to prevent the further loss of cartilage would be to maintain motion in the shoulder, because once it is lost, it's difficult to regain. Steps to reduce extreme pain in cases of bad shoulder arthritis can involve the doctor giving injections directly into the shoulder, or even shoulder surgery.

For patients with severe shoulder arthritis that does not respond to non-operative treatment, shoulder surgery can be very helpful. Depending on the condition of the shoulder and the specific expectations of the patient, surgical options include total shoulder joint replacement arthroplasty , ‘ream and run’ (humeral hemiarthroplasty with non prosthetic glenoid arthroplasty , and reverse (Delta) total shoulder joint replacement arthroplasty .

Knee MRIs should be avoided for knee pain without symptoms or effusion, unless there are non-successful results from a functional rehabilitation program.

If the knee is swollen and red and warm to the touch when compared to the other knee, a doctor may be concerned about inflammation due to rheumatoid arthritis or a crystalline arthritis, such as gout or pseudogout, or joint infection. Besides sending the joint fluid to a laboratory for analysis, blood tests may requested to determine a white blood cell count, erythrocyte sedimentation rate, and perhaps the level of C-reactive protein or uric acid. If blood tests reveal Lyme disease antibodies forming, the condition may be attributed to it.

An X-ray is useful to verify that there is no break or dislocation when there is a history of trauma. May show signs of osteoarthritis.

It is not always certain why arthritis of the knee develops. Most physicians believe that it is a combination of factors that can include muscle weakness, obesity, heredity, joint injury or stress, constant exposure to the cold, and aging. Cartilage in the knee begins to break down and leaves the bones of the knee rubbing against each other as you walk. Persons who work in a place that applies repetitive stress on the knees are at a high risk of developing this condition. Bone deformities increase the risk for osteoarthritis of the knee since the joints are already malformed and may contain defective cartilage. Having gout, rheumatoid arthritis, Paget's disease of bone or septic arthritis can increase your risk of developing osteoarthritis.

Some physicians and most podiatrist believe that Pes Planus (flat feet) cause increased rates and earlier incidence of knee osteoarthritis. In a study of army recruits with moderate to severe flat feet, the results showed that they had almost double the rate of knee arthritis when compared to recruits with normal arches.