When and why of knee replacement
Introduction
Anatomy:
The knee joint is the joint between the lower end of the femur (thigh bone) and the upper end of tibia (leg bone). The patella (kneecap) articulates with the femur and is an integral part of the quadriceps (extensor) mechanism. The articulating surfaces are covered by a layer of smooth and shock-absorbent tissue called hyaline cartilage. The joint is enclosed by a covering called the capsule. This is lined on its inner surface by a layer of synovium which secretes synovial fluid into the joint. This fluid lubricates the joint and provides nourishment to the hyaline cartilage. The knee derives its stability from ligaments that connect the bones (collateral and cruciate ligaments). It is controlled by the quadriceps muscle (extensor) and the hamstring muscles (flexors).
Arthritis:
Damage to the cartilage can occur due to age (osteoarthritis), inflammatory conditions (rheumatoid arthritis) or injuries (post-traumatic arthritis). Arthritis of the knee results in loss of cartilage which causes pain and limitation of movements. The quadriceps muscle becomes thinned and there is shortening of the medial collateral ligament, the joint capsule and the hamstring muscles resulting in bowleg deformity and contracture. In severe cases, the underlying bone can also get worn out. Rheumatoid arthritis also causes thinning (osteoporosis) of the bone.
Treatment of early arthritis:
Treatment of knee arthritis in early stages involves activity modification, weight reduction, use of knee brace, physiotherapy, medications and sometimes joint injections. These modalities give partial relief in early stages. However, the wear & tear process of arthritis continues and pain worsens and patient develops stiffness and deformities. At this stage a knee replacement is advised. The decision is taken after assessing the extent of patient’s pain and disability, the physical findings on examination, the severity of arthritis on x-rays and the response to non-operative treatment.
Treatment of severe arthritis:
- When arthritis becomes severe surgery is advised
- Arthroscopic debridement and lavage gives temporary relief of knee pain
- Osteotomy (realignment operation) can be considered as an alternative to knee replacement in selected patients
- Knee replacement is the treatment of choice as it gives far better results in terms of pain relief and function
Alternatives to knee replacement
Knee replacement: Indications
Knee replacement is recommended when there is:
- Severe pain which imposes limitation on activities of daily living like walking, getting into and out of a chair, getting up and down stairs, getting into and out of a car, going for shopping, attending family and religious functions, inability to sit on the floor or a low stool, etc.
- Pain at rest or night pains causing disturbed sleep
- Severe pain with minor jerk, twist or mis-step
- Difficulty in walking on uneven surfaces or on the road; inability to walk for more the 10-15 minutes or a few hundred feet; difficulty in travelling
- Persistent swelling and warmth in the knee
- Difficulty in bending the knee
- Inability to fully straighten the leg
- Bow-leg or knock-knee deformity at the knee
- Inability to tolerate medications
- Persistent pain in-spite of medications, brace, physiotherapy, injections, etc.
Age of the patient:
Knee replacement is generally recommended for patients over 60 years. The advanced age is not a bar to surgery. Many patients in their eighties successfully undergo knee replacement.
Many elderly patients have hypertension, diabetes, previous angioplasty or coronary bypass surgery, hypothyroidism, etc. Most of these patients can safely withstand knee replacement. Preoperative assessment by physician, cardiologist, endocrinologist and others may be necessary to optimize the patient’s condition.
Knee replacement can be done at a younger age as well. This decision is based on considering the individual circumstances of the patient – single versus multiple joint involvement, patient’s lifestyle and expectations, effects of arthritis on career, effects on marital life, economic responsibilities, family commitments, willingness to modify his/her lifestyle, etc. Some of these young patients will require a revision surgery at a later date.
Benefits of knee replacement:
- Provides complete and lasting relief of pain
- Improves quality of life
- Abolishes the need for painkillers
- Restores movement to the knee
- Enables activities of daily living without help
- Restores independence
- Enables outdoor activities like travelling, shopping, attending social functions, etc.
- Enables gainful employment
- Improves walking ability which has a positive impact on control of diabetes, hypertension, ischemic heart disease and obesity
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