Overview of Osteoarthritis

Osteoarthritis is a chronic disease affecting the synovial joints, particularly the large weight-bearing joints.

Prevalence (in US)
It is the most prevalent musculoskeletal condition that causes joint pain. The incidence of OA increases with age

•At age 18-24 years, 7% of men and 2% of women show signs of OA in the hands.
•At age 55-64 years, 28% of men and women show signs of OA in the knee, and 23% show signs of OA in the hip.
( Jane’s case – 57 yo, experienced intermittent pain in knee and hip)
•At age 65-74 years, 39% of men and women show signs of OA in the knee and 23% show signs of OA in the hip.
•At age 75-79 years, approximately 100% of men and women show some signs of OA.

There isn’t any significant correlation between incidence of OA and race, save for Chinese with a decrease of incidence of OA

Age wise, adults older than 55 years show radiographic evidence of osteoarthritis (OA). Males develop OA before age 45 years, possibly because of a higher incidence of posttraumatic OA.

After age 55 years, women are affected more frequently by OA and tend to have more severe disease than do men.

History

The usual complains that physician gets includes:
1.complain of insidious throbbing arthralgias with activity.
2.Resting relieves the pain initially, but eventually begins to suffer pain even when he/she is at rest.
3.Morning stiffness, which usually lasts less than 30 minutes(experienced in the joint).
4.Physician will most probably be able to feel intermittent joint swelling. Give-way weakness in the knees (ie, quadriceps pain inhibition)might be noted as well.

Signs & Symptoms

Early in the disease process (physical examination findings)
oJoints may appear normal.
oGait may be antalgic if weight-bearing joints are involved.
(Jane’s case – on standing, her pelvis dropped down on the other side when she stood on her painful leg. Elevated when stood on the good leg)

Later in the disease process ( physical examination findings)
oVisible osteophytes (out-growth of bone) may be noted.
oJoints may be warm to palpation.
oPalpable osteophytes frequently noted.
oJoint effusion frequently is evidenced in superficial joints.
oRange-of-motion limitations, due to bony restrictions and/or soft tissue contractures, are characteristic.
oCrepitus with range of motion not uncommon.
Causes?
•Primary osteoarthritis (OA), either localized or generalized, is most often idiopathic, except in rare cases in which a defective gene has been found to cause a familial form of OA.

•Secondary OA can be caused by the following:
o Obesity (increases mechanical stress)
o Repetitive use (ie, jobs requiring heavy labor and bending)
o Previous trauma (ie, posttraumatic OA)
o Infection
o Crystal deposition
o Acromegaly
o Previous rheumatoid arthritis (ie, burnt-out rheumatoid arthritis)
o Heritable metabolic causes (eg, alkaptonuria, hemochromatosis, Wilson disease)
o Hemoglobinopathies (eg, sickle cell disease, thalassemia)
o Neuropathic disorder leading to a Charcot joint (eg, syringomyelia, tabes dorsalis, diabetes)
o Underlying orthopedic disorders (eg, congenital hip dislocation, slipped femoral capital epiphysis)
o Disorders of bone (eg, Paget disease, avascular necrosis)

Pathophysiology

Traditionally, teaching prescribes that OA affects primarily the articular cartilage of synovial joints. Pathophysiologic changes occurs in the synovial fluid and the subchondral (underlying) bone and overlying joint capsule.
- Affected cartilage develops small tears (fibrillations) at articular surface

- Followed by large tears

- Eventually, cartilage fragments off into joints

The cartilage forming cells replicate to keep up with cartilage loss. Sadly, unable to do so eventually, so the underlying bone becomes exposed when gross areas of the bone become denuded of cartilage.

The osteoarthritic joint is characterized by decreased concentration of hyaluronic acid because of reduced production by synoviocytes and increased water content because of inflammation, particularly during later stages of the disease.
The onset of pain is usually insidious, is generally described as aching or throbbing, and may be the result of changes that have occurred over the previous 15-20 years of the patient's life. Most often, the pain worsens with activity involving the affected joint and is initially relieved with rest; eventually, however, pain occurs even at rest. Since cartilage itself is not innervated, the pain is presumed to arise from a combination of mechanisms, including the following:
• Osteophytic periosteal elevation
• Vascular congestion of subchondral bone, leading to increased intraosseous pressure
• Synovitis with activation of synovial membrane nociceptors
• Fatigue in muscles that cross the joint
• Overall joint contracture

Treatment

Lifestyle modification, particularly exercise and weight reduction, is a core component of the management of osteoarthritis (OA). Importance of strengthening all muscles that cross the given joint affected by OA should be emphasized.
Most research focuses on quadriceps strengthening in knee OA. Also important are stretching exercises, which increase range of motion. The importance of aerobic conditioning, particularly low-impact exercises (if OA affects weight-bearing joints), should be stressed.

Surgical interventions for OA of the hip
• Joint realignment (realignment osteotomy)
• Joint fusion (arthrodesis) - Surgically fusing the joint to eliminate motion
• Joint replacement (arthroplasty)
o Hip replacements generally are classified as either hemiarthroplasty (ie, replacement of the femoral side of the hip joint, while leaving the patient's acetabulum intact) or total hip arthroplasty (replacement of the femoral side of the hip joint and the acetabulum).
o Further classification often involves specification of the specific hardware used (eg, unipolar prosthesis, bipolar prosthesis) and whether or not cement is used to hold the hardware in place.

Medication

The American College of Rheumatology issued the following pharmacologic guidelines for the treatment of osteoarthritis of the hip and knee:
• Arthrocentesis with corticosteroid injection can be used only for knee OA if effusion is present.
• Up to 4 grams per day of acetaminophen can be administered. This is the preferred initial treatment for patients with OA.
• Topical anti-inflammatory medications or capsaicin can be administered only for knee OA.
• Low-dose nonsteroidal anti-inflammatory drugs (NSAIDs) (ie, analgesic doses) or nonacetylated salicylates may be indicated.
• Administer full-dose NSAIDs with misoprostol if risk factors for upper gastrointestinal bleeding are present.
• Narcotic analgesic use may be indicated in cases of severe pain.
• Simple analgesics
• Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have osteoarthritis.

Simple analgesics

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have osteoarthritis.
- Acetaminophen (Tylenol, Panadol, Feverall, Aspirin Free Anacin)
(*Jane takes paracetamol every afternoon which seemed to help for a few hours)

Topical analgesics
Topical analgesics are used for osteoarthritis involving relatively superficial joints, such as the knee joint and the joints of the hands. These agents are much less effective for deeper joints, such as the hip joint.
- Capsaicin (Dolorac, Capsin, Zostrix)

Nonsteroidal anti-inflammatory drugs
NSAIDs have analgesic, anti-inflammatory, and antipyretic activities. May inhibit COX activity and prostaglandin synthesis.
- Ibuprofen (Motrin, Advil, Nuprin, Rufen)
- Meloxicam (Mobic)

Cyclooxygenase-2 inhibitors
This class of medications can be particularly useful in the OA population, because patients in this group tend to be older and are therefore at increased risk for adverse GI effects due to NSAIDs.
- Celecoxib (Celebrex)

Opioid analgesics
These agents are used in patients whose pain has not been controlled with weaker analgesic medications. They are a particularly reasonable choice in patients who do not want joint replacement surgery.
- Oxycodone (OxyContin, Roxicodone)

Reference:
http://emedicine.medscape.com/article/305145-overview