Osteoarthritis Knee

By: Dr Om Prakash Shah Professor Department of OrthopaedicsRohilkhand Medical CollegeBareilly(U.P.)Ex HOD Dr SN Medical College, Jodhpur(Rajasthan)

DefinitionOsteoarthritis is a non-inflammatory, degenerative condition of joints Characterized

by degeneration of articular cartilage and formation of new bone i.e. osteophytes.

It is one of the main joint of the lower limb, and for the routine daily activities of the person it is a very important joint.

Classification of OA

Primary OA• More common than secondary OA• Cause –Unknown• Common-in elders where there is no previous pathology.• Its mainly due to wear and tear changes occuring in old ages mainly in

weight bearing joints.

Secondary OADue to a predisposing cause such as:1.Injury to the joint2.Previous infection3.RA4.CDH5.Deformity6.Obesity7.hyperthyriodism

Epidemiology

• Knee OA most common cause of disability in adults

• Decreased work productivity, frequent sick days

• Highest medical expenses of all arthritis conditions

• Due to habit of sitting cross-legged and squatting OA is more prevalent in

India.

• Symptomatic Knee OA

– More than 11% of persons > 64yr

Knee AnatomyThe knee joint is formed by femur, tibia and patella.

Pathology

OA is a degenerative condition primarily affecting the articular cartilage.

1. Articular cartilage

2. Bone

3. Synovial membrane

4. Capsule

5. Ligament

6. Muscle

Articular Cartilage-The lower end of the femur ( condyle of the femur) is covered by thick articular

cartilage about 0.5-1 cm in thickness. Similarly, upper end of the tibia (condyle of the tibia) is also covered by 0.5-1 cm thick articular cartilage.

Articular cartilage is a smooth, shiny and elastic structure and it serves the function of a shock absorber.

Cartilage is the 1st structure to be affected.Erosion occurs,often central & frequently in wt. bearing areas.

Right: Early OA with area of cartilage loss in the center.

Left: More advanced changes with extensive cartilage loss and exposed underlying bone

Changes in Bone

• Bone surface become hard & polished as there is loss of protection from the cartilage.

• Cystic cavities form in the subchondral bone because eburnated bone is brittle and microfractures occur.

• Venous congestion in the subchondral bone.

• Osteophytes form at the margin of the articular surface,which may get projected into the jt. Or into capsule & ligament,bone of the wt.-bearing jt.

• Tibial condyles become flatened, medial tibial condyle is more affected and depressed as the weight bearing line passes medially. Thus, giving rise to varus deformity.

A patient with typical OA of the knees. In the normal standing posture there is a mild varus angulation of the knee joints due to symmetrical OA of the medial tibiofemoral compartments

Knee joint Effusion

Synovial Membrane-• Synovial membrane undergo hypertrophy and become oedematous (which can

lead to ‘cold’ effusions).

• Reduction of synovial fluid secretion results in loss of nutrition and lubricating action of articular cartilage.

CapsuleIt undergoes fibrous degeneration and there are low-grade chronic inflammatory

changes.

Ligaments-• Undergoes fibrous degernation• There is low grade chronic inflammatory changes and acc.to the aspect joint

become contracted or elongated.

Muscles Undergoes atrophy,as pt. is not able to use the jt. Because of pain which further

limits movts. and function.

Risk Factors• Age (>45 yrs)• Female (more common in post-menopausal women)• Obesity ( most important modifiable)• Previous knee injury (specially previous trauma and sports injury)• Lower extremity malalignment• Habit of squatting and sitting cross-legged• High impact activities• Muscle weakness• Osteoporosis

Diagnosis of Knee OATests• FBC, ESR, RF• Arthrocentesis• X-rays (3 views)

– Weight-bearing AP – Lateral– Tangential Patellar (Sunrise)

• MRI

• Clinical symptoms Pain Joint Stiffness Swelling Crepitus Varus Deformity Synovial Thickening and effusion

• Synovial fluid1. WBC<2000/mm3

2. Clear color3. High Viscosity

• X-rays1. Osteophytes2. Loss of joint space3. Subchondral sclerosis4. Subchondral cysts

Pain and Tenderness– Usually slow onset of discomfort, with gradual and intermittent increase

– Pain is more on wt. bearing due to stress on the synovial membrane & later on due to bone surface,which r rich in nerve endings coming in contact.

-Initially relieved by rest but later on disturb sleep.-Diffuse/ sharp and stabbing local pain

– Types of pain

• Mechanical: increases with use of the joint

• Inflammatory phases

• Rest pain later on in 50%

• Night pain in 30% later on

Joint Stiffness-

– ‘Gelling’: stiffness after periods of inactivity, passes over within minutes (approx 15min.) of using joint again

– Coarse crepitus: palpate/hear (due to flaked cartilage & eburnated bone ends)

– Reduced ROM: capsular thickening and bony changes in joint,ms. Spasm or soft tissue contracture.

Kellegren Lawrence Grading

Management• Weight loss

– Nutrition referral

• Exercise Program (improves cartilage nutrition, muscle strength and prevents progression of OA and deformity)– Physiotherapy– Quadriceps strengthening – ROM exercises– Low impact activities e.g. swimming, biking – Avoid high stress activities (eg- jumping, running etc)

• Ambulatory assist devices– Cane– Walker

• Insoles

• Unloader knee braces

Medical Management• Chondroprotective agents - Glucosamine/Chondroitin/Collagen

polypeptide/Diacerin/Rosehip Powder (help in cartilage repair)• Acetaminophen• NSAIDs (Diclofenac, Aceclofenac, Indomethacin, Nimesulide)• Cox-2 inhibitors ( Celecoxib, Etoricoxib)• Opioids(Tramadol)• Intraarticular injections

– Glucocorticoids– Hyaluronans

• Anti-Osteoporotic treatment( Bisphosphonates, Calcium, Vit D3)• Anti- Oxidants ( Vit A, C, E, Se, Mn, Zn)

Management: AlgorithmLifestyle Modifications Acetaminophen

NSAIDs

Opioids

Celecoxib

Steroid Injections

Hyaluronan Injections

Surgical Referral

The use of shoes and insoles to reduce impact loading on lower limb joints. Modern sports shoes (‘trainers’) often have appropriate insoles. Alternatively, special heel or shoe insoles of sorbithane or viscoelastic materials can be used. They may help relieve pain as well as reducing the peak impact load on the joints during walking.

Surgical Management

High Tibial Osteotomy• Indication:

– Unicompartmental arthritis– Genu varus or valgus

• Realign mechanical axis

• Age < 60yo

• < 15 degrees deformity19

Partial Knee Arthroplasty• Indication:

– Unicompartmental arthritis

• Ligaments spared

• Increased ROM

• Faster recovery

• Prosthesis 10-yr survival: 84%

Total Knee Arthroplasty• Indication:

– Pain during rest is the strongest indication– Diffuse arthritis– Severe pain– Functional impairment

• Pain relief > functional gain• ACL sacrificed• PCL also may be sacrificed• Prosthesis 10-yr survival: 90%

Normal Knee Physiology• Cartilage- Sponge like action (deformation and reformation) Beneficial for the joint function Facilitates blood supply of the joint

• Synovial Fluid- Lubrication of the joint and the articular cartilage (secreted by the synovial membrane around the joint)

Smoothens the articular surface

• Healthy cartilage and good lubrication is necessary for smooth functioning and pain free movement of the joint

• Good mechanical axis is also necessary for smooth knee function

• Protein Diet• Multi-vitamins and multi- minerals• Green vegetables• Antioxidants, are necessary for repair of day to day wear and tear of the

cartilage and maintainance of healthy cartilage

Effect of Pressure over Knee joint

• Pressure = Force/Area

• With every 1 kg loss of weight pressure over the knee joint will be decreased by 4 times the normal

• While walking pressure over the knee joint- 4-5 times the normal pressure

• While running pressure over the knee joint- 6-7 times the normal pressure

• While going uphill (climbing stairs) pressure over the knee joint is 7 times the normal

• Squatting and sitting cross-legged decreases the contact area between the joint surface so resulting in increase of pressure over the joint.

Effect of cane support in OA knee

• The cane will shift the centre of gravity during weight bearing forward to the body, thus decreasing the pressure over the knee joint by balancing the pelvis.

• There is about 20% decrease in the pressure over the knee joint.

• The stick should be held in the hand of the same side that of the affected knee.

• The length of the stick should be upto the greater trochanter of the femur from the ground and the elbow should be in 15 degree flexion.

• The handle of the cane should be straight and not curved.

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