Osteoarthritis: my minimum evidence standard

Step 01

Osteoarthritis is classified in ICD-11 as a joint disease, coded joint by joint, and its pain as secondary to it

ICD-11 classification

In ICD-11, the World Health Organization's classification of diseases, osteoarthritis sits with the diseases of the musculoskeletal system, with a separate code for each joint. The pain it causes is classified separately, as chronic secondary musculoskeletal pain associated with structural changes: pain that is a consequence of the disease in the joint rather than a condition in its own right.

This matters for your file. The impairment is the joint disease, and pain is one of its effects. Because the impairment is different in a hip and a knee, and on one side or both, a strong file names the joints: which are affected, which is worst, and what each one stops you doing. That's much easier for the NDIS to read than a file that just says “osteoarthritis”.

This page covers the hip and knee. Osteoarthritis of the spine and of other joints is coded separately and isn't covered here.

The next step is what's driving the pain.

Step 02

Osteoarthritis pain comes mostly from the joint, and an x-ray doesn't show how much it hurts

Pain mechanism

Pain is classified by mechanism: nociceptive (from tissue), neuropathic (from nerve injury or disease), or nociplastic (from altered pain processing in the nervous system). In osteoarthritis, pain is mostly nociceptive. As the disease progresses, the bone, joint lining and joint capsule gain more nerve supply, nerves grow into cartilage, which normally has none, and inflammatory substances sensitise nociceptors, the nerve endings that respond to potential harm (Batchelor et al 2025). For some people, persistent input changes how the spinal cord and brain process it (central sensitisation), adding a nociplastic contribution.

That's why the x-ray doesn't measure the person. Some people with marked changes on an x-ray have little pain; some with mild changes have severe pain. Australia's Clinical Care Standard says imaging “does not significantly help with decisions on management, which should be guided by the person's functional abilities”. A strong file records pain and function directly, and treats imaging as background rather than proof.

The next step is the criteria the diagnosis is checked against.

Step 03

Osteoarthritis is diagnosed against the RACGP guideline for the knee and hip

Diagnostic criteria

AAPT has not published criteria for osteoarthritis. The Australian standards are the RACGP Guideline for the management of knee and hip osteoarthritis (2nd edition, 2018) and the Osteoarthritis of the Knee Clinical Care Standard (Australian Commission on Safety and Quality in Health Care, 2024). Both say osteoarthritis can be diagnosed clinically, without imaging: “Knee osteoarthritis can be diagnosed on clinical grounds alone” (Care Standard).

A strong file also records which other causes of joint pain were considered. These usually include inflammatory arthritis such as rheumatoid or psoriatic arthritis, gout, pain referred from the spine to the hip or knee, and bursitis or tendon problems around the joint. Some of these occur alongside osteoarthritis, and a file that says which joints and symptoms belong to which condition is much easier to read.

Once the diagnosis is settled, the question most refusals come down to is what has been tried.

Step 04

An osteoarthritis treatment history is easiest to read when it covers the nine elements of pain management

Treatment history · s 24(1)⁠(b)

Osteoarthritis isn't on the NDIS's List A or List B, so nothing about permanence is presumed. The NDIS treats it as degenerative: “For degenerative impairments, or those that get worse over time, we consider them permanent if treatment isn't likely to remedy the impairment. That is, the treatment won't cure the impairment or come close to removing its effects” (Operational Guideline, Applying to the NDIS). With osteoarthritis there's almost always another treatment someone can name: more exercise, weight loss, a medicine not yet tried, a joint replacement. So permanence turns on what your treating team writes about those options, and on whether surgery is realistic for you. I check the record against the nine elements of pain management (HEAPPPPSS). For each one, the table names a published source, Australian where one exists. For a support request, the same record shows where treatment ends and disability support begins, which is how the NDIS decides whether the health system should fund it instead.

For each element in your file, the NDIS looks for what was done and what happened, in pain and in function. For exercise and physiotherapy, that means the programme, how long it ran and what changed. For weight management, what support was offered and what happened. For medicines, what was tried, and why each was stopped or not suitable. For surgery, whether joint replacement has been considered for each affected joint, the surgeon's view, and the reason it isn't being done or the expected wait. If an element never appears, the file says nothing about it, and the NDIS decides what that silence means.

Permanence is one requirement. Function is the other one an osteoarthritis file most often has to show.

Osteoarthritis function is shown best across a whole day and the week that follows, not in one appointment

Function over time · s 24(1)⁠(c)

The cost of weight-bearing and repeated use often arrives later: the knee that managed the stairs at the appointment is swollen and stiff that night and the next morning. A strong file measures tolerances: how far you can walk, how long you can stand, how many stairs you can manage, whether you can kneel, get down to and up from the floor, and carry shopping, and what happens after each. It records which tasks can't be done, or need another person's help and how often, not only which are slower. A single appointment sees one task on one day, so it tends to make you look more capable than you are.

A strong file follows what happens after a run of ordinary activities. I follow up at 24 hours, 72 hours and 7 days.

For an access request, I then match what your file shows to the six activity domains in s 24(1)⁠(c), the areas of daily life the NDIS assesses. For a support request, the same record shows what the support keeps you doing and what slips without it. Either way, that's done for each person, not for each condition.

Five published osteoarthritis decisions show how files like this have fared at the Tribunal.