Osteoarthritis (OA)
Osteoarthritis (OA) is a chronic degenerative joint disorder characterised by progressive loss of articular cartilage, remodelling of subchondral bone and formation of osteophytes.
Causes and Risk Factors
There are 2 main types of OA: [Ref]
| Primary OA (more common) | OA develops without a clear identifiable underlying cause, usually due to age-related and mechanical degeneration
Risk factors include:
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| Secondary OA | OA develops in the background of a pre-existing joint abnormality, such as
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Pathophysiology
Primary pathological process: progressive degeneration of the articular cartilage
- Chondrocytes fail to maintain the cartilage matrix, causing proteoglycan loss and collagen breakdown
- The cartilage becomes thin, rough and less able to absorb mechanical stress
- Increased load is transferred to the underlying bone, causing subchondral sclerosis and subchondral cysts
- New bone forms at the joint margins, producing osteophytes
- Mild synovial inflammation may develop, contributing to pain, stiffness and joint swelling
Disclaimer:
This pathophysiology is simplified for exam-level learning. Although OA is commonly described as beginning with progressive articular cartilage degeneration, it is not simply a passive “wear-and-tear” process or a disease of cartilage alone.
OA is now considered a heterogeneous whole-joint disease involving abnormal chondrocyte activity, low-grade predominantly innate immune-mediated inflammation, synovitis, subchondral bone remodelling, osteophyte formation and altered joint biomechanics. Changes s in the synovium or subchondral bone may sometimes occur before obvious cartilage loss. [Ref]
Joint Involvement / Distribution
OA typically affects the following joints: [Ref]
- Knee joint
- Hip joint
- Small joints of the hand (1st CMC, PIP, DIP joints)
- Cervical and lumbar spine joints (usually facet joints)
Clinical Features
General / Non-Specific Features
Symptoms typically develop gradually over months or years
- Activity-related joint pain (i.e. pain that is brought on or worsened by joint movement)
- Morning stiffness lasting <30 min
- Symptoms causing functional impairment
Important features that distinguish OA from inflammatory arthritis (e.g. RA)
| Feature | Osteoarthritis | Inflammatory arthritis |
|---|---|---|
| Pain pattern |
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| Morning stiffness |
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| Symmetry (of the affected joints) |
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Joint-Specific OA Findings
| Affected joint | Findings |
|---|---|
| Knee OA | Typically bilateral and symmetrical. Medial tibiofemoral compartment knee OA is more common than lateral compartment OA
Symptoms:
Signs:
Features seen in advanced disease:
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| Hip OA | Symptoms:
Signs:
Features seen in advanced disease:
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| Hand OA | Hand OA is typically bilateral
Symptoms:
Specific deformities based on joint involvement:
In contrast to osteoarthritis, rheumatoid arthritis typically spares the DIP joints in the hands (+ feet). |
Complications
- Chronic pain
- Joint deformity
- Functional limitations
- Psychosocial impact
Investigation and Diagnosis
OA can be diagnosed clinically (without imaging) if ALL of the following are present:
- ≥45 y/o
- Activity-related joint pain
- Morning joint stiffness lasting <30 min
Do not routinely use imaging to diagnose osteoarthritis unless there are atypical features or features that suggest an alternative or additional diagnosis.
X-ray in OA
Typical radiological features of OA: (LOSS)
- Loss of joint space (or narrowing)
- Osteophyte formation
- Subchondral sclerosis
- Subchondral cysts
Note: structural changes on X-ray may not correlate with the presence or severity of symptoms or degree of functional impairment.
Management
Conservative / General Management
Offer:
- Weight management – if the patient is overweight / obese
- Advise that any amount of weight loss is beneficial but losing 10% is likely better than 5%
- Therapeutic exercise tailored to patients (e.g. local muscle strengthening, general aerobic fitness)
Consider:
- Manual therapy in hip / knee OA alongside therapeutic exercise
- Walking aids if there is lower limb OA
Do not routinely offer an aid or device (insoles / braces / tape / splints / supports), unless there is:
- Joint instability or abnormal biomechanical loading AND
- Therapeutic exercise is ineffective or unsuitable without it AND
- The addition of it is likely to improve movement and function
NICE recommends NOT to offer:
- Acupuncture
- Dry needling
- Electrotherapy (including transcutaneous electrical nerve stimulation, ultrasound therapy, interferential therapy, laser therapy, pulsed short-wave therapy, neuromuscular electrical stimulation)
Pharmacological Management
Pharmacological management should always be used alongside non-pharmacological options and at the lowest effective dose for the shortest possible time:
- Step 1: topical NSAID (useful for knee OA, but maybe less effective for other forms of OA)
- Step 2: oral NSAID with gastroprotection
- Step 3: paracetamol or weak opioid for short-term pain relief and infrequent use only
- Step 4: intra-articular corticosteroid injections (explain that it only provides 2-10 weeks of pain relief)
NICE recommends NOT to offer:
- Glucosamine (explain there is no strong evidence of benefit)
- Strong opioids (explain that the risks outweigh the benefits)
- Intra-articular hyaluronan injections
Surgical Management
Consider referring patients with knee / hip / shoulder OA for joint replacement if:
- Symptoms substantially impact quality of life, AND
- Non-surgical management is ineffective / unsuitable
Do not exclude people with OA from referral for joint replacement because of:
- Age
- Sex or gender
- Smoking
- Comorbidities
- Overweight or obesity, based on measurements such as BMI
NICE recommends NOT to offer arthroscopic lavage or debridement for OA.
References