Osteoarthritis

Osteoarthritis (OA) is a common, chronic joint condition resulting in degeneration of the joint cartilage.

Pathophysiology

• Cartilage tissue is a form of connective tissue which allows bones to slide over each other smoothly, and also helps in shock-absorbing.
• Cartilage is comprised of chondrocytes embedded in an extracellular matrix high in glycosaminoglycans and proteoglycans, which interacts with various things including collagen.
• The most common form of cartilage is hyaline cartilage, which is mainly compromised of type II collagen.
• Normally, the matrix is continuously remodelled due to degrading enzymes – matrix metalloproteinases. However, these are not so highly expressed, so the overall volume of cartilage is maintained.
• In OA, there is an imbalance in matrix synthesis and degradation, with a net degradation resulting in loss of proteoglycans and collagen.
• This results in cartilage loss, and exposure of the subchondral bone that lies underneath.
• This is what causes the pathological changes we see in OA:
  • Loss of joint space
  • Osteophytes: Bony spurs which form from unstressed cartilage proliferating and then ossifying, likely in attempts to maintain an even articulating surface.
  • Subchondral cysts: Form in the areas of subchondral bone which are exposed and under stress.
  • Subchondral sclerosis: Increased bone density in the bone just below the cartilage.

Risk Factors

• Primary OA: No obvious cause
  • Increasing age
  • Obesity
  • Female gender
• Secondary OA: Occurring due to pre-existing disease.
  • History of avascular necrosis
  • History of inflammatory/infectious arthritis
  • History of injury to the joint/overuse e.g., from occupation

Clinical Features

• Commonly affected joints: Hip joint, knee joint, small joints of the hands/feet
• Pain: Gets worse with activity
• Stiffness: Usually worse after rest or in the morning, but does not usually last >30 minutes in the morning
• Reduced range of motion
• Crepitus during movement
• Heberden’s nodes: Swollen distal interphalangeal joints
• Bouchard nodes: Swollen proximal interphalangeal joints
• Squaring at the base of the thumb
• Joint effusion: Usually only affects the knee
• Muscle wasting

Differential Diagnosis

• Rheumatoid arthritis: Pain and stiffness tend to improve with activity, and there is usually >30 minutes of morning joint stiffness.
• Septic arthritis: Patient is clinically unwell with systemic symptoms alongside a red, hot, swollen and painful joint.
• Gout: Often affects the large toe with acute attacks resulting in redness, swelling, warmth, and pain of the joint.

Investigations

OA can be clinically diagnosed without investigations in patients >45 who have no morning stiffness/morning stiffness <30 minutes and have pain that increases with activity. However, in case of diagnostic uncertainty, the following can be helpful:

Bloods

ESR: Can be done to rule out inflammatory arthritis

Rheumatoid factor/anti-CCP: If querying rheumatoid arthritis

Imaging

Plain film radiograph: An X-ray can show the aforementioned features of OA – loss of joint space, osteophytes, subchondral cysts, and subchondral sclerosis. They are not done routinely for diagnosis or for non-surgical management.

Management

Conservative

Weight loss if patients are overweight

Exercise

Local hot/ice packs

Medical

• Topical NSAIDs: First-line treatment for knee OA. It can also be considered for other types of OA.
• Oral NSAIDs: Offered when topical drugs are ineffective or cannot be used.
  • Should be used for as little time as possible.
  • Patients should be offered a PPI alongside the NSAID if prescribed.
  • Risk factors for GI complications/renal/hepatic/cardio toxicity need to be taken into account.
• Paracetamol/weak opioids: Not routinely offered unless other treatments cannot be used, or they are to be used in the short-term for OA flare ups.
  • NICE found no improvement in pain/quality of life in paracetamol compared to placebo, hence it is not recommended as a routine drug.
  • Strong opioids are not offered.
• Intra-articular steroid injections: These can provide analgesic relief in the short-term and are used when other pharmacological treatments have failed.

MDT

• Physiotherapy
• Occupational therapist: Home adaptations such as bath aids/rising-recliners may be appropriate, or alternatively simple walking aids or walkers.
• Podiatry: Can advise for orthotics i.e. adjusted footwear to assist with pain and walking
• Pain clinic: Some patients may benefit from a referral to a pain clinic if their pain is not being well controlled despite optimised medical and surgical management.
• Psychiatric services: Patients may develop anxiety/depression alongside their disease. Although this can initially be managed in primary care, if it is insufficiently managed, psychiatry involvement may be required.

Surgery

• Joint replacement: A common procedure that results in new articulating surfaces.
• Arthrodesis (joint fusion): Involves fusing two bones, thus removing motion from the joint and potentially relieving pain.
• Osteotomy: Involves cutting and reshaping of bone to shift weight and pressure.
• Arthroscopic lavage and debridement: NICE recommend against this treatment for oA.

References

https://www.ncbi.nlm.nih.gov/books/NBK482326/#:~:text=Go%20to%3A-,Pathophysiology,that%20eventually%20mediate%20joint%20destruction.

https://www.hopkinsarthritis.org/arthritis-info/osteoarthritis/oa-pathophysiology/

https://www.nice.org.uk/guidance/ng226/resources/visual-summary-on-the-management-of-osteoarthritis-pdf-11251842157

https://cks.nice.org.uk/topics/osteoarthritis/management/management/

https://www.hss.edu/condition-list_arthrodesis.asp

https://orthoinfo.aaos.org/en/treatment/osteotomy-of-the-knee/