What is OA?

Osteoarthritis (OA) is a common chronic joint disease characterised by changes in the articular cartilage's composition, structure, and function.

OA is viewed as a whole of joint disease and is not simply a cartilage-driven disease. Although loss of articular cartilage is a key characteristic, changes may occur in the subchondral bone, menisci, ligaments, joint capsule, synovium, and the surrounding muscles.

OA has an inflammatory component as well and not just about joints “wearing out”. For example, in knee OA, cartilage loss does not explain people’s pain and cartilage lacks a nerve innervation and blood supply. Joint inflammation may contribute to pain and central adiposity induces chronic low grade systematic inflammation.

There are many risk factors for why people get OA (incident OA) and why people get worse (progression of OA).

It is important to think about modifiable risk factors (body weight, knee injury, joint overload, muscle weakness, physical inactivity) and non-modifiable risk factors (age, sex, genetics)

OA diagnosis

The diagnosis of knee OA may be made using a combination of clinical, radiographic, or arthroscopic evaluation
In clinical practice, guidelines recommend that knee OA should be diagnosed based on the clinical examination alone and in the first instance without imaging investigations (NICE Guidelines, 2022).
For GLA:D, a clinical diagnosis of OA is required- a person does not need an Xray or MRI to confirm OA to be eligible for the program.

Common Clinical Approaches to Diagnosing Knee OA

The following are a few commonly used methods for making a clinical diagnosis of knee OA:

NICE Clinical Criteria (2022)
- Activity-related knee pain.
- Age 45 years or older.
- No morning joint-related stiffness, or morning stiffness lasting no longer than 30 minutes.
American College of Rheumatology (ACR) Clinical Criteria
- Knee pain plus a combination of features such as:
  - Age over 50 years.
  - Morning stiffness less than 30 minutes.
  - Crepitus on active movement.
  - Bony tenderness.
  - Bony enlargement.
  - No palpable warmth of the joint.

Role of imaging in clinical practice

Limited role in clinical practice
Only required if diagnosis is uncertain or after exhausting all non-surgical interventions
Poor relationship between imaging findings and symptoms
Degenerative meniscal and labral tears are often found on imaging in people with and without hip or knee pain
Tears are part of OA
OA better explained with a biopsychosocial model than a biomedical model eg various factors contribute to pain

Kellgren Laurence (KL system) is a common method for classifying the severity of knee OA on X-ray. It is sometimes used in research and by orthopaedic surgeons to describe structural disease severity and is graded from 0-4.

KL Grade	Radiographic Features
0	No radiographic features of OA
1	Doubtful joint space narrowing and possible osteophyte formation
2	Definite osteophytes and possible joint space narrowing
3	Multiple osteophytes, definite joint space narrowing, sclerosis, possible bony deformity
4	Large osteophytes, marked joint space narrowing, severe sclerosis, definite bony deformity

Clinical features of osteoarthritis

Pain
Stiffness
Long history of problems/intermittent flares
Morning stiffness (should improve < 30 mins)
Affect sleep, quality of life
Depression anxiety common in 1/5 people
Multiple joints involved (> 2-3)

Difference between meniscal tears, degenerative meniscal tears and osteoarthritis

Meniscal tears are among the most common MRI findings in people with knee pain.
However, decades of research show that:

Many meniscal tears are incidental
Many tears are not the primary source of pain
Degenerative meniscal tears may be part of a broader joint disease process

Clear understanding prevents:

Misdiagnosis
Over‑reliance on imaging
Unnecessary surgery
Poor patient education

Types of meniscal tears

A. Traumatic meniscal tears

Sudden, high‑load or twisting injury
Often in younger people
Often longitudinal, vertical, or bucket‑handle
May cause true mechanical symptoms (locking)

B. Degenerative meniscal tears (tissue‑level concept)

A degenerative meniscal tear describes:
Gradual, age‑ and load‑related meniscal tissue failure
Often horizontal or complex tear patterns
Often atraumatic
Frequently asymptomatic

This term describes how the meniscus fails, not whether the knee has osteoarthritis.

Degenerative tears:

Can occur with pain or without pain
Can occur with OA or without OA
Become more prevalent with age

Key Message:

Degenerative meniscal tears are common and frequently asymptomatic and often represent early joint changes along an osteoarthritis continuum rather than an isolated cause of knee pain. High‑quality trials show no long‑term benefit of arthroscopic partial meniscectomy over exercise therapy, and international consensus recommends conservative management as first‑line care (Culvenor et al., 2019; Englund et al., 2008; Ghouri et al., 2022; Noorduyn et al., 2022; Sihvonen et al., 2020).

For most people with degenerative meniscal tears, physiotherapy‑led education and exercise targeting the whole joint provides equal or superior long‑term outcomes compared with arthroscopy.
Although osteoarthritis may present in different joints and at different stages, first‑line management is broadly consistent across presentations. Education, exercise therapy, and addressing modifiable risk factors should be fully implemented and progressed before imaging‑driven or surgical pathways are considered.
Consider whether all appropriate first‑line conservative interventions been adequately explored, tailored, and progressed?

Table: Differences between traumatic meniscal tears, degenerative meniscal tears, and knee osteoarthritis

Feature	Acute (Traumatic) Meniscal Tear	Degenerative Meniscal Tear	OA Knee (± Meniscal Tear)
Primary lens	Injury to the meniscus	Meniscal tissue degeneration	Whole‑joint disease
Typical age	Younger adults (often <40 yrs)	Mid‑life onward (can appear in late 30s)	Usually diagnosed ≥45 yrs, but biology may precede
Onset	Sudden, clear injury event	Gradual or insidious	Gradual, episodic, fluctuating
Trauma history	Yes (twist, pivot, hyperflexion)	Often none or trivial	Often absent or remote
Primary pathology	Discrete structural tear	Intrinsic meniscal tissue failure	Multi‑tissue degeneration
Meniscus role	Main injured structure	Primary affected tissue	One of several affected tissues
OA required?	No	No	Yes (by definition)
Relationship to OA	Can increase future OA risk	May represent early joint change	Meniscal tears are a feature of OA
Tear morphology (typical)	Vertical, longitudinal, bucket‑handle	Horizontal, complex, fraying	Complex tears, maceration, extrusion
Mechanical symptoms	Possible true mechanical block (locking)	Catching common; true locking rare	Often nonspecific; true locking uncommon
Pain attribution	Tear often clinically relevant	Tear often incidental	Pain is multifactorial
Structure–symptom link	Stronger (but not perfect)	Weak	Weak for meniscus alone
MRI relevance	Helps guide diagnosis	Often over‑interpreted	Poor pain discriminator
Natural history	May heal, persist, or displace	Often stable unless part of OA process	Progressive disease course (variable rate)
Surgical logic	Repair or selected surgery may be indicated	Rarely indicated without true mechanical block	Arthroscopy not indicated
First‑line management	Rehab ± surgical referral	Education + exercise therapy	OA‑based care
Key teaching label	Injury model	Tissue failure model	Whole‑joint disease model

References:

Couldrick, J. M. (2025). Who benefits most? Evaluating clinical and biomechanical outcomes following structured education and exercise therapy interventions for people with knee osteoarthritis The University of Canberra]. Canberra, ACT. https://doi.org/10.26191/19ee-yc73

Culvenor, A. G., Oiestad, B. E., Hart, H. F., Stefanik, J. J., Guermazi, A., & Crossley, K. M. (2019). Prevalence of knee osteoarthritis features on magnetic resonance imaging in asymptomatic uninjured adults: a systematic review and meta-analysis. British Journal of Sports Medicine, 53(20), 1268-1278. https://doi.org/10.1136/bjsports-2018-099257

Englund, M., Guermazi, A., Gale, D., Hunter, D. J., Aliabadi, P., Clancy, M., & Felson, D. T. (2008). Incidental Meniscal Findings on Knee MRI in Middle-Aged and Elderly Persons. New England Journal of Medicine, 359(11), 1108-1115. https://doi.org/doi:10.1056/NEJMoa0800777

Englund, M., Roemer, F. W., Hayashi, D., Crema, M. D., & Guermazi, A. (2012). Meniscus pathology, osteoarthritis and the treatment controversy. Nature Reviews Rheumatology, 8(7), 412-419. https://doi.org/10.1038/nrrheum.2012.69

Ghouri, A., Muzumdar, S., Barr, A. J., Robinson, E., Murdoch, C., Kingsbury, S. R., & Conaghan, P. G. (2022). The relationship between meniscal pathologies, cartilage loss, joint replacement and pain in knee osteoarthritis: a systematic review. Osteoarthritis and Cartilage, 30(10), 1287-1327. https://doi.org/10.1016/j.joca.2022.08.002

Noorduyn, J. C. A., van de Graaf, V. A., Willigenburg, N. W., Scholten-Peeters, G. G. M., Kret, E. J., van Dijk, R. A., Buchbinder, R., Hawker, G. A., Coppieters, M. W., Poolman, R. W., & Group, E. R. (2022). Effect of Physical Therapy vs Arthroscopic Partial Meniscectomy in People With Degenerative Meniscal Tears: Five-Year Follow-up of the ESCAPE Randomized Clinical Trial. JAMA Network Open, 5(7), e2220394-e2220394. https://doi.org/10.1001/jamanetworkopen.2022.20394

Sihvonen, R., Paavola, M., Malmivaara, A., Itälä, A., Joukainen, A., Kalske, J., Nurmi, H., Kumm, J., Sillanpää, N., Kiekara, T., Turkiewicz, A., Toivonen, P., Englund, M., Taimela, S., & Järvinen, T. L. N. (2020). Arthroscopic partial meniscectomy for a degenerative meniscus tear: a 5 year follow-up of the placebo-surgery controlled FIDELITY (Finnish Degenerative Meniscus Lesion Study) trial. British Journal of Sports Medicine, 54(22), 1332-1339. https://doi.org/10.1136/bjsports-2020-102813

Skou, S. T., Holmich, P., Lind, M., Jensen, H. P., Jensen, C., Garval, M., & Thorlund, J. B. (2022). Early Surgery or Exercise and Education

for Meniscal Tears in Young Adults. NEJM Evid, 1(2), EVIDoa2100038. https://doi.org/10.1056/EVIDoa2100038