Osteoarthritis of knee is a degenerative condition where cartilage layer gets thinned out or eroded due to degeneration and the bone underneath it get exposed. It is the most common cause of knee pain in middle aged population. It is closely related to aging but not directly as a consequence of aging.
Knee joint is the largest synovial joint of the body and bears weight of the body with maximum shearing forces involved. It is formed by lower end of thigh bone, upper end of leg bone and knee cap, a special type of bone that forms within muscle tendon. All these three bone are covered with thick cartilage layer, which is pain insensitive, tough, resistance to shearing force and have the capacity to absorb impact. There are two ‘C’ shaped structures is placed between thigh bone and leg bone, named meniscus. Meniscus increases the congruity of the joint and also helps in absorbing impact, thus protects the cartilage layer. The joint is filled with viscous synovial fluid which provides nutrition to the cartilage and facilitates smooth gliding of the bone surfaces during movement. Stability of the joint is maintained by different ligaments, two are inside the joint and others are on outer surface of the joint.
Knee joint Anatomy
Knee pain due to osteoarthritis is the second most common cause for orthopaedic outpatient visit. Eighty percent of the population above 65 years of age may have some form of osteoarthritic changes of their knee but only 60% of them need medical attention for their symptom. Females are more prone than male. There is no specific cause for osteoarthritis but some risk factors are associated with it.
In the beginning cartilage become soft and its surface starts fraying. With progress of the disease cartilage starts thinning off and ultimately erodes off exposing the underlying bone. The exposed bone rubs with each other during knee movements and weight bearing evokes pain as bone is full of pain sensitive nerve endings where as cartilage do not have any nerve supply. This loss of cartilage height creates lot of space between the bone surfaces which is not supported and ligament becomes lax results in joint instability and deformity. Initially this deformity is correctable, with progression of disease it becomes fixed.
Damaged cartilage of osteoarthritic knee
First and common presentation is pain which is off and on in the beginning associated with stiffness on rest. Later the pain become persistent which aggravate with activity and subsides on rest. There may be swelling of the joint. As the disease progress joint starts getting deformed and movement restricted. In very advance stage it may become awkwardly deformed for mobility.
Osteoarthritis knee
X-ray of knee in three plane to evaluate the joint space in stress is the primary requirement. MRI may require in early stage when x-ray is not conclusive or symptom not matched with x-ray presentation. MRI can detect meniscal injury or torn cartilage flap which can be the cause of acute pain. Blood tests are done to rule out any inflammatory condition or other cause of arthritis. X-ray wise osteoarthritis is described in 4 grades 0 to 4. Grade 0 is normal knee whereas Garde 4 is advance stage with total loss of cartilage. Grade 4 is very wide in representation starting from focal loss of cartilage reasonably shaped knee to totally deformed mangled knee.
Treatment of osteoarthritis of knee is directed to improve the quality of life by reducing pain with medication, lifestyle modification, physical therapy and orthotics. Patient education to understand the disease and its progression so that one can cop up with the intended changes that is required to adopt. This measures is effective in early stage of disease. Intra articular injection of PRP and hyaluronic acid also gives good pain relief. In moderate grade of disease surgical correction of joint alignment can prevent the progression of disease. Arthroscopic debridement of degenerated torn meniscus cartilage flap and microfracture also give good symptomatic relief if these are the cause of symptom. In advance stage none of these measures may not be adequate to improve quality of life and surgical intervention like total joint replacement is required to reduce pain and improve joint function and thus quality of life.
Total Knee Replacement
Uni Condylar Knee Replacement
