Knee Osteoarthritis

 DEFINITION

• Osteoarthritis is a pathology associated with inflammation in the joints of the body. In the case of knee 

osteoarthritis, the arthritis and inflammation most commonly affects the tibiofemoral or patellofemoral joints, leading to knee pain.

• Osteoarthritis 

is a term derived from the Greek word osteo, meaning “of the bone,” arthro meaning “joint,” and itis meaning inflammation,even though the amount of inflammation present in the joint can range from excessive to little or no inflammation.

Knee , joint , Osteoarthritis

SYNONYMS

• Knee arthritis

• Knee degenerative joint disease

ETIOLOGY

• The wearing down of the hyaline cartilage leads to an inflammatory response.

There is thickening and sclerosis of the subchondral bone and development of osteophytes or bone spurs. This leads to a narrowing of the joint space, loss of shock absorption, and ultimately pain.

• Daily wear and tear in combination with various injuries sustained throughout life is the most common cause of the breakdown of healthy tissue.

• Degeneration of the cartilage and resultant arthritis can also be the result of other factors such as trauma or joint injury.

• At a cellular level, as a person ages, the number of proteoglycans in the articular cartilage decreases. Proteoglycans are hydrophilic and work within cartilage to bind water. With the reduction of proteoglycans comes a decrease in water content within the cartilage and a corresponding loss of cartilage resilience. With the decreases in

cartilage resilience,collagen fibers of the cartilage become susceptible to degradation and injury. The breakdown of collagen and other cartilage tissue are released into the surround joint space. Inflammation results as the body attempts to respond to the influx of byproducts from cartilage injury.

• As the cartilage degrades,the jointspace narrows and ligaments become more lax. In response to the laxity, new bone outgrowths,called spurs or osteophytes, can form on the margins of the joints in an attempt to improve the congruence and passive stability of the articular cartilage surfaces.

Articular , Degeneration , Cartilage , wear

• Primary osteoarthritis

refers to joint degradation resulting from aging and tissue degeneration.

• Secondary osteoarthritis

refers to joint degradation and tissue degeneration that results from factors other than aging such as obesity, trauma, and congenital disorders.

• Stages of knee osteoarthritis: 

 - Stage I (mild): 

Mild joint space narrowing, cartilage fissuring.

- Stage II (moderate):

 Cartilage erosion,

osteophytes, sclerosis, and moderate joint space narrowing.

- Stage III (moderate severe):

Significant jointspace narrowing,larger and more numerous osteophytes,

sclerosis, and significant cartilage erosion.

- Stage IV (severe): 

Obliteration of joint space, large osteophytes, significant sclerosis, complete erosion of cartilage, and large osteophytes.

EPIDEMIOLOGY AND 

DEMOGRAPHICS

• The Framingham study has revealed that radiographic knee osteoarthritis occurs in at least 33% of persons aged 60 years and older.

• Approximately 6% of 30-year-old adults have knee pain from osteoarthritis on most days; 10% to 15% of 60-year-old adults have this same pain.

• As the American population gets older and more overweight, the prevalence will grow.

• 70% of all individuals older than 70 years of age have x-ray evidence. Only one-third to one-half has symptoms.

• Changes can usually be seen in persons older than 30 years, with significant impairments noted in persons older than 50 years.

• In general, there is a higher prevalence of osteoarthritis in women than in men after the age of 50 years. For persons with diagnosed osteoarthritis before the age of 50 years,there are more men than women.

• Whites andAfricanAmericans have similar prevalence, but African Americans may be more disabled from their pathology. Chinese Americans have a higher prevalence of knee osteoarthritis than Whites. Few data are found about Hispanic Americans, but it is theorized that the prevalence is high.

• 200,000 knee replacements are performed each year.

MECHANISM OF INJURY

• Osteoarthritis is a pathology of over-use. The mechanism of injury is therefore the result of repetitive motions that stress the hip joint.The more cycles of an activity that the ankle performs, the more likely the result will be anatomical damage.

• Daily use/misuse of the knee.

• Misalignment of the tibiofemoral joint or patellofemoral joint.

• Excessive use/strain of the knee secondary to work, obesity or recreational activities.

• Injuries, such as fracture and strains/sprains, that cause inflammation and scar tissue in the knee.

• Poor foot or hip mechanics.

COMMON SIGNS AND 

SYMPTOMS

• Deep pain in the knee.

• Difficulty localizing the exact location of the pain.

• Stiffness in the knee with inactivity.

• Cracking or deep crunching in the knee.

• Inflammation and thickening of the knee.

• Knee flexion contracture.

• Joint deformity (valgus or varus).

• Pain tends to be localized to the affected joints (usually anterior knee or on either joint line) and surrounding tissues.

• Studies have shown subjectively that inactivity stiffness, pain on using stairs, and night pain have high reliability

(0.80 to 0.90 kappa value) are predictors of knee osteoarthritis.

Stiffness , Pain , Deformity

AGGRAVATING ACTIVITIES

• Inactivity leads to stiffness.

• Weight-bearing activities (walking, running, dancing, jumping, etc.).

• Long-term standing,especially on harder surfaces like concrete.

• Poor footwear (i.e., high heels).

• Inactivity allows the inflammation to “pool” and increase pressure, leading to discomfort and loss of available movement.

• Joint movement increases “wear and tear” and inflammation/irritation of the articular surfaces. The more compression involved with the movement, the more “wear and tear” and irritation will occur.

EASING ACTIVITIES

• Rest

• Pain-free motion of the knee joint

• Gentle stretching and exercise, use of heat/ice,massage,taking antiinflammatory medication,nonweightbearing positions, and ankle elevation

• Generally speaking,these activities lead to decreased wear and tear, increased joint lubrication, and loss of stiffness and inflammation associated with this condition.

24-HOUR SYMPTOM PATTERN

• Stiffness in the morning.

• Better after a warm shower and taking medication.

• Can worsen with excessive movement.

• Stiffens again in the evening.

• Deep achiness in the knee at night described as throbbing.

PAST HISTORY FOR THE REGION

• Jobs or recreational activitiesthatrequire excessive use/strain of the knee (walking, running, jumping, dancing, baseball catcher, etc.)

• Prior history to injury in either the foot or hip.

• Prior history of injury to the knee.

• Obesity

• Prior history of knee surgery.

Physical EXAMINATION

• Genu valgum or genu varum

• Decreased weight bearing noted during stance phase of gait

• Decreased knee flexion during swing phase of motion

• Joint thickening (bony changes and inflammation)

Genu , Crepitud , Joint

• Loss of knee ROM: End-range flexion and extension may be limited.

• Localized pain when palpating the medial and lateral margins of the patella and when palpating the tibiofemoral joint line

• Loss of joint mobility when testing tibiofemoral or patellofemoral accessory motions

• Crepitus with movement with patello-femoral osteoarthritis

IMPORTANT OBJECTIVE TESTS

• Alignment assessment

• AROM and passive ROM (PROM)

• Joint mobility

• Special tests: Ligament stability, meniscal integrity, and patellar grind

• Strength tests

• In studies focusing on knee osteoarthritis, the following tests have the highest reliability factor in predicting pathology:

 Medial instability test at full knee extension (0.66 kappa value).

 Lateral instability test at full knee extension (0.88 kappa value).

 Values are less for instability tests when knee is flexed slightly.

 Posterior drawer test (0.82 kappavalue).

DIFFERENTIAL 

DIAGNOSIS

• Knee sprain

• Tendinitis (patellar, iliotibial, or pes anserine)

• Bursitis (patellar,pes anserine)

• RA

• Septic arthritis

• Meniscal injury

• Ligament injury

• Fracture

• Referral from the lumbar region

CONTRIBUTING FACTORS

• The knee is designed to handle normal daily use.When factors change the body’s ability to respond to normal forces, damage occurs.

• Uncontrolled risk factors that contribute or predispose an individual to knee osteoarthritis pathology:

 Gender (females > males)

  Age (increase 2%/year after age 40 years).

 Genetics

 Prior history of injury to either lower extremity.

 Prior history of childhood hip pathology.

 Leg length discrepancies

• Modifiable risk factors that contribute or predispose an individual to continue or progress ankle osteoarthritis include the following: 

 Weight

 Work or recreational activities

 Repetitive or significant traumatic injuries to the hip.

 Poor health (smoking, long-term use of steroids)

 Muscle or tissue restrictions such as tight ITB, calf, or hip flexors.

TREATMENT

SURGICAL OPTIONS

• Arthroscopic debridement for mild-to-moderate symptoms

• Total knee replacement (TKA)

Knee , Arthroplasty , Replace

• Noncemented for younger (40 to 50 years of age) patients.

• Cemented for older or overweight patients.

• Replacement tends to last 15 to 20 years.

• Osteotomy (for deformity) for young patients to postpone the need for arthroplasty.

• Osteochondral drilling

REHABILITATION

• Rehabilitation should focus on the following:

 Education in correct use of ice/heat at home for pain abatement and edema control

 Implementation of a home exercise program.

 Teach proper footwear with or without orthotics.Correction of foot alignment and reduction of loading on the joint are important factors related to hip osteoarthritis.

 Manual therapy (STM, joint mobilization) can improve joint mobility and arthrokinematics and decrease pain.

 Massage can decrease pain by relaxing muscular tension, improving circulation, and increasing endorphin release.

• Pathological changes to cartilage cannot be repaired by the body at this time Even surgical advances have yet to solve the problems associated with cartilage damage. With this in mind, rehabilitation should focus on decreasing the stress placed on the damaged cartilage and correcting biomechanical and anatomical abnormalities that may predispose an individual to increased stress at the knee joint.

• The clinician should also evaluate the patient for leg length discrepancies that would cause abnormal stresses to placed on the hip joint.Shoe lifts can be recommended to equalize the length of the legs during function.

• The knee joint is a synovial joint. Therefore the cartilage has the potential to heal. Joint motion can influence the healing process. It is aggravated by activities that excessively load the joint, but motion in a non–weight-bearing to a limited weight-bearing environment can greatly decrease the patient’s symptoms.

• Exercises include the following:

 Stretches: Calf (gastrocnemius and soleus), quadriceps,ITB, hamstrings.

 Strengthening exercises: Quadriceps (VMO),hamstrings,hip abductors,hip adductors, hip extensors.

 Proprioceptive exercises

 Cardiovascular exercises: Bicycle progressing to treadmill to promote circulation and healing.

• Exercise creates a sense of control over the symptoms and the condition.

• Modalities: Ice/heat, ultrasound, electrical stimulation, and tape/braces can be used as adjuncts to improve the healing environment.

• Factors that contribute to abnormal joint mechanics and loading should be determined and addressed.

PROGNOSIS

• Long-term prognosis for a patient with knee osteoarthritis depends on the extent of wear and tear and ability to reduce the joint strain placed on the joint (posture, activity, etc).

• For the most part, knee osteoarthritis is degenerative condition. At earlierstages of the pathology, rehabilitation aimed at reducing the load placed on the joint can potentially slow or halt the progression of degeneration.

• For patients who are further along in the degenerative process, outcomes will be less favorable because cartilage has only a limited ability to repair itself.

SIGNS AND SYMPTOMS  INDICATING REFERRAL TO PHYSICIAN

• Unrelenting pain

• Unusual responses to therapy

• Neurological signs

• Red flag symptoms such as excessive redness and swelling and generalized malaise and fatigue.

• Infection

SUGGESTED READINGS

1- Amin S. Cigarette smoking and the risk for cartilage loss and knee pain in men with knee osteoarthritis. Ann Rheum Dis. 2007;66(1):18–22. 

2- St Clair SF, Higuera C, Krebs V, Tadross NA,Dumpe J, Barsoum WK. Hip and knee arthro-plasty in the geriatric population. Clin Geriatr Med. 2006;22(3):515–533.

3- Dugan SA. Exercise for health and wellness at midlife and beyond: balancing benefits and risks. Phys Med Rehabil Clin N Am. 2007;18(3):555–575.