Unicompartmental Knee Replacement
Unicompartmental or partial knee replacement is a surgical procedure where the worn out or damaged surfaces of one side of the knee joint is removed and resurfaced with metal and plastic components.
What is Arthritis?
The knee is made up of the femur (thighbone), the tibia (shinbone), and patella (kneecap). The surfaces of all these bones are covered in articular cartilage which serves as a cushion and helps absorb shock during motion. The menisci - the soft cartilage between the femur and tibia – also serve as further ‘protection’ for the joint surfaces. With time (age) or following significant knee injuries this articular cartilage can thin and ultimately expose the bone surfaces. This process is “arthritis” and it can lead to extreme pain and difficulty in performing daily activities In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. These factors can cause pain and restricted range of motion in the joint. Osteoarthritis is a type of arthritis. The knee joint is composed of 3 ‘compartments’ – the medial (inner), the lateral (outer) and the patella-femoral (knee cap) – and typically (in about 50% patients) the disease is confined to the medial (inner) aspect of the knee. If the symptoms are also confined to this one compartment then a unicompartmental knee replacement should be recommended.
Your doctor may recommend surgery if non-surgical treatment options have failed to relieve the symptoms.
Causes of Arthritis
The exact cause is unknown, however there are several factors that are commonly associated with the onset of arthritis and may include:
- Injury or trauma (fractures) to the joint
- Increased body weight
- Repetitive overuse
- Joint infection
- Inflammation of the joint
- Connective tissue disorders
Symptoms of Arthritis
Arthritis of the knees can cause knee pain, which may increase after activities such as walking, stair climbing, or kneeling. The joint may become stiff and swollen, limiting the range of motion. Knee deformities such as knock-knees and bow-legs may also occur if the disease is predominantly in one side of the knee.
Diagnosis of Arthritis
Your doctor will diagnose osteoarthritis based on the medical history, physical examination, and X-rays.
X-rays typically show a narrowing of joint space in the arthritic knee.
Indications for Unicompartmental Knee Replacement
Traditionally, total knee replacement was commonly indicated for severe osteoarthritis of the knee. In total knee replacement, all worn out or damaged surfaces of the knee joint are removed and replaced with new artificial parts. Partial knee replacement is a surgical option if your arthritis is confined to a single compartment of your knee.
Unicompartmental Knee Replacement Procedure
During the surgery, a small incision is made over the knee to expose the affected compartment of the knee joint. Your surgeon will remove the remaining meniscus, and a small amount of the diseased tibial (shin) bone surface. No bone is resected from the femur making it a true resurfacing procedure. The plastic tibial component is placed into the new prepared area and is secured with bone cement. Now the remainder of the articular cartilage is removed from the femur which then accommodates the new metal component which is fixed in place using bone cement. Once the femoral and tibial components are fixed in proper place the knee is taken through a range of movements. The incision is then closed.
Postoperative Care Following Unicompartmental Knee Replacement
The recovery from a unicompartmental knee replacement is quicker than following a total knee replacement and the patient’s final perception of their knee much improved. It tends to require only a 2 day hospital stay but this could be shorter depending on the patient. You will be able to fully weight bear with crutches from day 1 and may need crutches for 2 weeks (approx.) after surgery. A physical therapist will advise you on an exercise program to follow for 4 to 6 months to help regain the range of motion and restore your strength. You may perform exercises such as walking, swimming and biking but high impact activities such as jogging should be avoided.
Risks and Complications Following Surgery for Unicompartmental Knee Replacement
Possible risks and complications associated with unicompartmental knee replacement include:
- Knee stiffness
- Blood clots (Deep vein thrombosis)
- Nerve and blood vessel damage
- Loosening of the implant
Click here for Unicompartmental Knee Replacement - Procedure Information Booklet
Advantages of Unicompartmental Knee Replacement
The significant advantages of Unicompartmental Knee Replacement over Total Knee Replacement include:
- Smaller incision
- Less blood loss
- Quick recovery
- Less postoperative pain
- Better overall range of motion
- Feels more like a natural knee
It has been shown that the risks of all major post-operative complications are HALF that of total knee replacement.