OSTEOARTHRITIS
OSTEO-ARTHRITIS
Osteoarthritis (OA) is a chronic disease process affecting synovial joints, particularly large weight-bearing joints.
OA is particularly common in older patients but can occur in younger patients either through a genetic mechanism or, more commonly, because of previous joint trauma.
PATHOPHYSIOLOGY
Joints can be classified as synovial, fibrous, or combination joints, based on the presence or absence of a synovial membrane and the amount of motion that occurs in the joint.
Normal synovial joints allow a significant amount of motion along their extremely smooth articular surface. These joints are composed of a synovial membrane, articular or hyaline cartilage, subchondral bone, synovial fluid, and a joint capsule.
Although traditional teaching prescribes that osteoarthritis (OA) affects primarily the articular cartilage of synovial joints, pathophysiologic changes also occur in the synovial fluid, as well as in the underlying (subchondral) bone and the overlying joint capsule.
The affected cartilage initially develops small tears, known as fibrillations, at the articular surface, followed by larger tears; the cartilage eventually fragments off into joints. The cartilage-forming cells (ie, chondrocytes) replicate in an attempt to keep up with the cartilage loss; however, they eventually are unable to do so, and the underlying bone becomes exposed as gross areas of the bone become denuded of cartilage.
In the early degenerative process, increased expression and content of various metalloproteinases occur. These proteinases are very much involved in the excessive matrix degradation that characterizes cartilage degeneration in OA.
Bone along the periphery of the joint replicates to form osteophytes, while the subchondral bone along the midportion of the joint becomes sclerotic, and areas within it may eventually undergo cystic degeneration because of focal resorption.
Synovial fluid is formed through an ultrafiltration process of serum by cells that form the synovial membrane (synoviocytes).
Synovial cells also manufacture the major protein component of synovial fluid, hyaluronic acid (also known as hyaluronate). Synovial fluid supplies nutrients to the avascular articular cartilage; it also provides the viscosity needed to absorb shock from slow movements, as well as the elasticity required to absorb shock from rapid movements.
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
In addition to the underlying pathophysiologic changes described above, overall, the joint may undergo mechanical deformation, with resultant malalignment and instability. Alternatively, the joint can ankylose.
FREQUENCY
Osteoarthritis (OA) is the most prevalent musculoskeletal condition that causes joint pain. The incidence of OA increases with age, with estimates based on radiologic evidence indicating the following incidence patterns:
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.
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.
MORTALITY/MORBIDITY
Mortality does not occur directly from osteoarthritis (OA), but it can result indirectly from complications associated with immobility and deconditioning, medications used to relieve pain associated with OA, or from joint-related surgery.
Morbidity can take the form of pain or loss of function.
SEX
Osteoarthritis (OA) is equally prevalent in men and women aged 45-55 years. After age 55 years, the prevalence of OA increases in women in comparison with men. The primary differences in incidence between males and females are related to the sites affected by OA.
The most common sites affected in females are distal interphalangeal joints, proximal interphalangeal joints, first carpometacarpal joints, metatarsophalangeal joints, hips (in those aged 55-64 y), and knees (in those aged 65-74 y). In males aged 65-74 years, the hips and knees are affected more frequently than they are in females.
AGE
Most 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.
CLINICAL
HISTORY
Patients with osteoarthritis (OA) generally complain of insidious throbbing arthralgias with activity. Although initially, resting relieves the pain, the patient eventually begins to suffer pain even when he/she is at rest.
Morning stiffness, which usually lasts less than 30 minutes, may also be experienced in the joint. Intermittent joint swelling and give-way weakness in the knees (ie, quadriceps pain inhibition) are noted.
PHYSICAL
Early in the disease process of osteoarthritis, physical examination findings include the following:
Joints may appear normal.
Gait may be antalgic if weight-bearing joints are involved.
Later in the disease process, physical examination findings include the following:
Visible osteophytes may be noted.
Joints may be warm to palpation.
Palpable osteophytes frequently are noted.
Joint effusion frequently is evidenced in superficial joints.
Range-of-motion limitations, because of bony restrictions and/or soft tissue contractures, are characteristic.
Crepitus with range of motion is not uncommon.
CAUSES
Primary osteoarthritis (OA), which can be 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:
Obesity (increases mechanical stress)
Repetitive use (ie, jobs requiring heavy labor and bending)
Previous trauma (ie, posttraumatic OA)
Infection
Crystal deposition
Acromegaly
Previous rheumatoid arthritis (ie, burnt-out RA)
Heritable metabolic causes (eg, alkaptonuria, hemochromatosis, Wilson disease)
Hemoglobinopathies (eg, sickle cell disease, thalassemia)
Neuropathic disorder leading to a Charcot joint (eg, Syringomyelia, tabes dorsalis, diabetes)
Underlying orthopedic disorders (eg, congenital hip dislocation, slipped femoral capital epiphysis)
Disorders of bone (eg, Paget disease, avascular necrosis)
LABORATORY STUDIES
Research has not yet produced a clinically useful diagnostic test for osteoarthritis (OA), so no laboratory studies can assist in the condition's diagnosis per se.
Researchers have looked at monoclonal antibodies, synovial fluid markers, and urinary pyridinium cross-links (ie, breakdown products of cartilage). Erythrocyte sedimentation rate (ESR) is not usually elevated, but it may be slightly elevated in cases of erosive inflammatory arthritis.
IMAGING STUDIES
Ø Studies on the diagnostic use of magnetic resonance imaging (MRI) in osteoarthritis (OA) of the knee are currently being conducted. A study attempted to correlate the clinical features of OA with MRI findings in patients with the condition. A large joint effusion was associated with pain and stiffness. The presence of an osteophyte in the patellofemoral compartment was associated with pain. All other imaging findings, including focal or diffuse cartilaginous abnormalities, subchondral cysts, bone marrow edema, subluxation of the meniscus, meniscal tears, and Baker cysts, were not associated with symptoms.
Ø Bone scans may be helpful in the early diagnosis of OA of the hand. Bone scans also can help to differentiate joint pain due to OA from pain associated with other disease processes. For example, bone scans typically yield a symmetrical pattern of a very mild increased uptake in a symmetrical manner in OA. In contrast, bone scans are often negative in the early stages of multiple myeloma, a cause of bone pain in older adults that can be confused with OA. Bone scans also can help to differentiate OA from osteomyelitis and bone metastases. Single-photon emission computed tomography scanning (SPECT) helps to differentiate back pain due to degenerative disk disease from back pain due to spondylolysis.
Ø Plain radiographs are often negative early in the disease.
Ø The Kellgren-Lawrence Grading System, which is the most universally accepted method of classifying radiographic osteoarthritis, uses the following 4 radiographic features:
Joint space narrowing
Osteophytes
Subchondral sclerosis
Subchondral cysts
OTHER TESTS
Perform diagnostic joint aspiration for synovial fluid analysis to help rule out conditions other than osteoarthritis. The presence of noninflammatory joint fluid helps to distinguish OA from other causes of joint pain. Other findings that aid in the differentiation of OA from other conditions are negative Gram stains and cultures, as well as the absence of crystals when fluid is viewed under a polarized microscope.
TREATMENT
PHYSICAL THERAPY
Lifestyle modification, particularly exercise and weight reduction, is a core component of the management of osteoarthritis (OA). A program of physical therapy should emphasize the importance of strengthening all muscles that cross the given joint affected by OA.
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. Swimming, especially aerobic aquatic programs can be helpful. Certain studies also indicate that a home exercise program for patients with OA of the knee provides an important benefit.
In a study of patients with knee osteoarthritis, Jan et al found that, in most respects, non – weight-bearing exercise was as therapeutically effective as weight-bearing exercise. After an 8-week exercise
program, patients in the weight-bearing and non – weight-bearing groups showed equally significant improvements in function, walking speed, and muscle torque. However, patients in the weight-bearing group demonstrated greater improvement in position sense, which may help patients with complex walking tasks, such as walking on a spongy surface.
In terms of reducing osteoarthritis-related knee pain, Chaipinyo and Karoonsupcharoen found no significant difference between home-based strength training and home-based balance training. However,
more improvement in knee-related quality of life was noted in the strength-training group than in the balance-training group.
Use of assistive devices for ambulation and for activities of daily living may be indicated. Braces and appropriate footwear may also be of some use.
A cane can be used in the opposite hand for OA of the hip, and a cane in the hand of comfort may be helpful for OA of the knee. The patient can be taught joint-protection and energy conservation techniques.
Other physical therapy modalities include electrotherapy and thermotherapy.
OCCUPATIONAL THERAPY
Evaluation of how well the patient performs his/her activities of daily living, as well as retraining of the patient, can be assisted by the occupational therapist. Emphasize joint-protection techniques. Hand splinting, especially of the first carpometacarpal joint, may be indicated.
RECREATIONAL THERAPY
A home exercise program that incorporates all of the above treatment principles could be designed and implemented to help the patient with osteoarthritis retain mobility.
COMPLICATIONS
Osteophyte formation in the spine can lead to radiculopathy and/or myelopathy. Osteophyte formation in the cervical spine near the vertebral arteries can lead to vertebral artery compression.
SURGICAL INTERVENTION
Surgical intervention for osteoarthritis (OA) may be indicated. Types of procedures vary according to the site and the degree of involvement. The types of surgical interventions that can be employed include the following:
Surgical interventions for OA of the knee
Arthroscopic lavage - Using a saline lavage to wash out the joint
Joint realignment (realignment osteotomy)
Joint fusion (arthrodesis) - Surgically fusing the joint to eliminate motion
Joint replacement (arthroplasty)
Surgical interventions for OA of the hip
Joint realignment (realignment osteotomy)
Joint fusion (arthrodesis) - Surgically fusing the joint to eliminate motion
Joint replacement (arthroplasty)
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).
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.
OTHER TREATMENT
Intra-articular steroid injections may provide pain relief and have an anti-inflammatory effect on the affected joint in osteoarthritis (OA).
Such injections generally result in a clinically and statistically significant reduction in osteoarthritic knee pain as soon as 1 week after injection. The effect may last, on average, anywhere from 4-6 weeks per injection, but this benefit is unlikely to continue beyond that time frame.
Some controversial evidence exists regarding frequent steroid injections and subsequent damage to cartilage (chondrodegeneration). Therefore, usually no more than 3 injections are recommended per year in any 1 osteoarthritic joint.
Intra-articular injection of sodium hyaluronate (ie, hyaluronic acid [HA], hyaluronan), also referred to as viscosupplementation, has been shown to be safe and effective for the symptomatic relief of knee OA.
Interestingly, the duration of residence of an intra-articular injection (days) cannot explain the prolonged clinical benefit (months), and accordingly, subsequent biological mechanisms have also been proposed that may play an important role in the clinical benefit.
The combination of quadriceps strengthening and HAs may have a synergistic effect on pain.
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 ease, and have sedating properties, which are beneficial for patients who have osteoarthritis.
ACETAMINOPHEN (Tylenol, Panadol)
Dosage:
Adult - 325-1000 mg PO q4-6h prn; not to exceed 4000 mg/d in patient with normal hepatic function
CAPSAICIN (Dolorac, Capsin, Zostrix)
Topical analgesic of choice in OA; capsaicin is derived from plants of the Solanaceae family. It may render skin and joints insensitive to pain by depleting substance P in peripheral sensory neurons. Capsaicin must be used for at least 2 weeks for the full effects to be appreciated.
Salicylates creams and topical NSAIDs are available.
Dosage:
Adult - 4 applications/day; good pain relief with bid application
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
For external use only; avoid contact with eyes; do not use tight bandage; discontinue use if condition worsens or symptoms persist for 14-28 d
IBUPROFEN (Motrin, Advil, Nuprin, Rufen)
After the very early stages of OA, inflammation begins to play a role. Thus, medications with a combination of analgesic and anti-inflammatory properties become more desirable, at least in theory.
Dosage:
Adult - 200-800 mg PO tid/qid
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in congestive heart failure, hypertension, and decreased renal and hepatic function; caution in anticoagulation abnormalities or during anticoagulant therapy
MELOXICAM (Mobic)
To some extent, more selective for COX-2 receptors, compared with traditional NSAIDs. Meloxicam decreases the activity of COX, which in turn inhibits prostaglandin synthesis. These effects decrease the formation of inflammatory mediators.
Dosage:
Adult - 7.5 mg PO qd; may increase to 15 mg PO qd
CELECOXIB (Celebrex)
Inhibits primarily COX-2. Considered an inducible isoenzyme, COX-2 is induced during pain and inflammatory stimuli. The inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, the COX-1 isoenzyme is not inhibited; thus, GI toxicity may be decreased. Seek the lowest dose of celecoxib for each patient.
Dosage:
Adult - 200 mg/d PO qd; alternatively, 100 mg PO bid
OXYCODONE (OxyContin, Roxicodone)
Pure narcotic analgesics, such as oxycodone, might be the initial DOC. Eventually; this short-acting narcotic can be switched to a long-acting transdermal preparation, such as fentanyl (Duragesic patch).
Dosage:
Adult - 5 mg PO q6h prn
PROGNOSIS
The prognosis is good for patients with osteoarthritis who have undergone joint replacement. The prosthesis may need revision 10-15 years after its installation, depending on the patient's activity level.
PATIENT EDUCATION
Patient education is one of the primary therapeutic approaches to osteoarthritis (OA). Several Arthritis Foundation studies have demonstrated that education in OA benefits the patient. Through education, patients can institute ways to reduce pain and increase joint function. Emphasize the need for physician follow-up visits.