QuestionSBA
QuestionChoice
Osteoarthritis is a degenerative arthritis caused by wearing of the articular cartilage. Risk factors include old age and obesity. It typically presents with a long gradual onset of pain and stiffness in affected joints. Distribution can be asymmetrical or symmetrical. Examination findings include reduced range of motion, swelling and crepitus. In the hip, internal rotation is often the first movement to become painful. According to NICE, the diagnosis is confirmed in a patient with all of the following:

- ≥45 years old
- Activity related joint pain
- No morning stiffness / <30 minutes of morning stiffness

This patient meets these criteria and, as such, can be diagnosed with osteoarthritis. Initial management for osteoarthritis includes conservative (weight loss, exercise) and medical (first line: paracetamol) measures, with surgery considered later in disease (arthroplasty)
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Osteoarthritis
QuestionChoice
Ankylosing spondylitis is a HLA-B27 associated inflammatory arthritis. It presents with inflammatory joint pain and >30 minutes of morning stiffness. Symptoms are improved by exercise and worsened by rest. In addition, it is an axial spondyloarthropathy. This means it typically affects the spine, with other features including sacroiliac pain. In this case, there is no back pain. This makes ankylosing spondylitis much less likely
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Ankylosing spondylitis
QuestionChoice
Rheumatoid arthritis is an inflammatory arthritis. It presents with inflammatory joint pain, with >30 minutes of morning stiffness. Pain and stiffness tend to be improved by exercise and worsened by rest. In addition, although rheumatoid arthritis can affect the hip, it is a less likely site to be affected. More typical sites for early rheumatoid arthritis include the hands, feet and wrists
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Rheumatoid arthritis
QuestionChoice
Septic arthritis describes an infection of a joint, which can be life-threatening. Septic arthritis typically presents with pain and swelling over hours to days. There are also no other systemic features like fever or sepsis, which may be present with septic arthritis (although their absence does not rule out septic arthritis)
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Septic arthritis
QuestionChoice
Systemic lupus erythematosus (SLE) is a connective tissue disease that presents with inflammatory arthritis. It presents with inflammatory joint pain, >30 minutes of morning stiffness and pain and stiffness is improved by exercise and worsened by rest. In addition, there are often other extra-articular features in SLE, including fatigue, fever, weight loss, alopecia, malar rash, pericarditis, pleural effusion, blood abnormalities, and neurological involvement. There is also an association with antiphospholipid syndrome. None of these features are present in this case, making a diagnosis of SLE less likely
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Systemic lupus erythematosus
Concept
Chapter
# Summary

Osteoarthritis (OA) is a chronic, degenerative joint disease characterised by loss of articular cartilage, remodelling of bone with osteophyte formation and mild synovitis. The main risk factor is older age, although obesity, joint injury and genetics also contribute. Presentation is with gradual onset pain that is worse with activity, with associated functional limitations. The most commonly affected joints are the knees, hips and small joints of the hands. Diagnosis is clinical, and severity of disease on X-ray does not correlate well with severity of symptoms. Management should be individualised, with important components being exercise, simple analgesia and optimisation of risk factors (such as maintaining a healthy weight). Where there is ongoing pain and disability, options include intra-articular steroid injections and surgical intervention (such as joint replacement).

# Definition

Osteoarthritis (OA) is the commonest form of arthritis, which is characterised by degenerative changes affecting the entirety of joints affected. Cartilage is lost, the subchondral bone becomes sclerosed with formation of osteophytes and subchondral cysts and there is inflammation of the synovial membrane lining the joint capsule (synovitis). 

# Epidemiology

- Approximately 10 million people in the UK have osteoarthritis
- More women than men are affected
- Average age of onset is 55 
- The commonest joint affected is the knee, followed by the hip then the hand

# Aetiology

Osteoarthritis develops due to a combination of factors, with important contributors including:

- Older age
- Female sex
- Overweight or obesity
- Family history of OA
- Previous joint injury
- Joint damage due to inflammation (e.g. in patients with inflammatory arthritis)
- Physical inactivity and reduced muscle strength
- Low bone density 
- Deformities such as development dysplasia of the hip or leg length discrepancy
- Stresses on joints due to occupational factors (e.g. repetitive squatting or kneeling) or exercise

# Signs and Symptoms

Key symptoms include:

- Pain in the affected joint exacerbated by use
- Pain may radiate e.g to the thigh, knee and ankle in hip OA, or to the wrist in hand OA
- Joints may feel stiff (although prolonged morning stiffness is suggestive of inflammatory arthritis)
- Functional limitations such as difficulty opening jars (hand OA) or mobilising (knee or hip OA)
- Locking or giving way of the knee

Examination findings include:

- Restricted and painful range of motion (e.g. in hip OA internal rotation with the hip flexed is particularly painful)
- Crepitus (friction between bone and cartilage) 
- Affected joints may appear swollen or enlarged
- A small effusion may form, especially when the knee is affected
- Synovitis may present with mild soft tissue swelling, tenderness and warmth
- Muscle wasting and weakness can result from disuse atrophy
- Joint instability
- An antalgic gait ("limping") in knee OA
- Trendelenburg gait in hip OA (due to weak abductors patients lurch towards the affected hip)
- Deformities, including:
- Heberden's nodes (bony nodules over the distal interphalangeal joints) 
- Bouchard's nodes (bony nodules over the proximal interphalangeal joints) 
- Fixed flexion of the first carpometacarpal joint with hyperextension of the distal joints
- This may lead to squaring of the joint with subluxation and remodelling
- Ulnar or radial deviation of joints in the hand may occur
- In severe hip OA the leg may be shortened due to fixed flexion and external rotation
- Varus (most commonly) or valgus deformities of the knees 

# Differential Diagnosis

- **Inflammatory arthritis** such as rheumatoid arthritis, ankylosing spondylitis; pain that improves with activity and morning stiffness lasting over 30 minutes are differentiating factors, systemic symptoms such as malaise and weight loss may be present
- **Septic arthritis** is an important differential for all patients presenting with an acutely painful swollen joint (which may occur in an acute flare of osteoarthritis); patients may be systemically unwell with fevers
- **Fracture** e.g. of the tibial plateau may mimic OA symptoms of pain and limited mobility; usually the patient is unable to weight bear with swelling of the affected area; a history of trauma should be elicited
- **Malignancy** including bone metastases, multiple myeloma or sarcoma may cause mechanical pain leading to functional limitations; red flags include weight loss, night sweats, persistent pain not relieved by rest and night pain
- **Greater trochanteric pain syndrome** most commonly occurs in middle-aged women and causes lateral hip pain and tenderness worsened by activity; it may also radiate to the lateral knee
- **Iliotibial band syndrome** presents with lateral knee pain worse with activity, which is often accompanied by clicking or clunking sounds when the knee is moved; occurs most commonly due to repetitive knee flexion e.g. cyclists or runners 
- **Meniscal tear** may occur after an injury involving a twisting or pivoting movement; similar symptoms of pain, swelling, locking and giving way of the knee and range of motion may be limited on examination
- **Trigger thumb** may mimic OA of the hand with pain, clicking and catching when the thumb is flexed; a nodule may be palpable in the tendon
- **Ganglion cysts** occur more commonly in people with OA and present as soft tissue swellings e.g. at the base of the thumb; often asymptomatic but may cause pain and limit movement of the joint

# Investigations

Diagnosis of OA is clinical and can be made without any investigations in a patient of 45 or older if there are no features suggesting another underlying cause of symptoms.

If there is diagnostic uncertainty or a rapid deterioration in symptoms, **X-rays** of affected joints may be of use. Typical findings can be remembered with the mnemonic "LOSS":

- **L**oss or narrowing of joint space due to thinning of cartilage
- **O**steophytes i.e. formation of new bony spurs at the joint margins
- **S**ubchondral sclerosis i.e. increased bone density beneath the cartilage
- **S**ubchondral cysts which are fluid-filled sacs in the subchondral bone

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However, severity of OA features on X-ray may not correlate well with severity of clinical disease.

Other investigations if the diagnosis is in doubt should be targeted to the differential suspected, and may include:

- Further imaging such as MRI to look for ligament or cartilage damage (e.g. a meniscal tear)
- Joint aspiration with synovial fluid analysis to exclude septic arthritis or crystal arthritis
- Blood tests for inflammatory markers, rheumatoid factor and anti-CCP (for example) if rheumatoid arthritis is suspected

Baseline bloods for renal function and full blood count should be considered in all patients starting NSAID treatment, especially older patients who are at higher risk of adverse effects.

# Management

**Conservative management:**

- Patient education and advice on self-care e.g. appropriate footwear
- Weight loss advice and signposting to services in patients with excess body weight
- Exercise has many benefits including strengthening muscles, improving fitness, reducing pain and improving function
- Options include online fitness programmes designed for people with arthritis, physiotherapy and supervised exercise sessions
- Physiotherapy services may also be able to offer manual therapies and joint supports such as braces or splints to reduce load and improve instability
- Occupational health input may be needed in patients with functional impairment to assess their working environment and suggest adaptations
- Patients should be asked about psychosocial stressors and support offered e.g. for associated depression and anxiety
- Occupational therapy input may be helpful to advise on aids and devices to assist with activities of daily living (e.g. walking sticks, sock aids, grab rails, tap turners)
- Podiatry input may be useful to assess the biomechanics of joint pain and advise on orthotic devices such as insoles
- Referral to a pain management service may be appropriate for patients who have not responded to maximal medical (and if appropriate, surgical) management of OA
- Assess falls risk and consider referral to specialist services for patients at risk (e.g. those with abnormal gait or balance, or who have had a fall in the last year)

**Medical management:**

- First-line analgesia is with topical NSAIDs (such as ibuprofen gel) - patients should be made aware that some systemic absorption may occur
- If this is ineffective or unsuitable, oral NSAIDs should be considered (with a PPI for gastroprotection if there are risk factors for gastrointestinal side effects)
- Paracetamol or weak opioids (e.g. codeine) may also be used in the short-term
- Topical capsaicin is another option, especially for knee OA
- Intra-articular steroid injections may be considered if other treatments are not effective, and/or to enable therapeutic exercise

**Surgical management:**

- Patients with OA of the hip, knee or shoulder who have symptoms significantly impacting quality of life despite optimal medical management should be considered for orthopaedic referral
- The usual operation offered is an arthroplasty (joint replacement)
- Rehabilitation before and after surgery is key to optimising outcomes

# Complications

- Joint deformities (as above)
- Increased risk of falls
- Functional limitations, e.g. hand OA may making writing, turning keys or fasting buttons challenging
- Reduced mobility 
- Sleep difficulties
- Low mood and anxiety
- Chronic pain

# Prognosis

- Not all cases of OA are progressive and the disease course is variable
- OA of the hands generally has a good prognosis, especially interphalangeal joint involvement
- Hip OA has a poorer prognosis with many patients requiring arthroplasty
- Knee arthroplasties for OA are also common however many patients' symptoms improve or remain stable with time 
- Intermittent flares of OA may occur, where symptoms increase in intensity suddenly
- Flares tend to last for a few days before improving

# NICE Guidelines

[NICE CKS - Osteoarthritis](https://cks.nice.org.uk/topics/osteoarthritis)

[NICE - Osteoarthritis in over 16s: diagnosis and management](https://www.nice.org.uk/guidance/ng226/)

# References

[WHO fact sheet - Osteoarthritis](https://www.who.int/news-room/fact-sheets/detail/osteoarthritis)

[BNF Treatment Summaries - Osteoarthritis](https://bnf.nice.org.uk/treatment-summaries/osteoarthritis/)

[Patient UK - Osteoarthritis](https://patient.info/doctor/osteoarthritis-pro)
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A 77-year-old man presents to his GP complaining of right hip pain. This has been gradually getting worse over the last two years is worsened by movement. He is stiff for around 20 minutes in the morning. On examination, he has a large body habitus and has pain upon internal rotation of the right hip.

What is the most likely diagnosis?
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