Unicondylar Knee Replacement

Partial knee replacement

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Unicompartmental knee arthroplasty

Unicompartmental arthroplasty (UKA), also called partial knee replacement, is an option for certain patients. A division is made of the knee into three compartments: medial (the inside part of the knee), lateral (the outside), and patellofemoral (the joint between the kneecap and the thighbone). Most patients with arthritis, who are severe enough to be considered for knee replacement have been shown to have significant wear in two or more of the above compartments and are best treated with total knee replacement. A minority of patients (probably between 10 and 30 percent) have wear confined primarily to one compartment, mostly the medial may be candidates for unicompartmental knee replacement.  The advantages of UKA compared to TKA include smaller incisions,

better post-operative range of motion, easier post-op rehabilitation, less blood loss, shorter hospital stay, lower risk of infection, stiffness, and blood clots. There may be a requirement for harder revision. Recent research suggests that UKA, if done properly in certain patients ensure survival rates that are comparable to TKA. Many surgeons believe that TKA is the more reliable method in the long term. Patients who have infectious or inflammatory arthritis such as Rheumatoid, Lupus, Psoriatic or marked deformity are not suitable for this surgery.

Post Surgery Recovery

Post surgery hospitalization varies from two days to seven days on average, which depends on the health status of the person and the amount of support that is available at home.  Protected weight bearing with a walker is started within few hours till enough muscle strength has been regained to come on a stick. Patients typically undergo several weeks of physical therapy and to restore motion, function and strength. Frequently the range of motion is recovered over the first two weeks. By six weeks, the patients progress to full weight bearing using a cane. Total post-operative recovery will take up to three months. Some patients have been noticed to improve only after many months.


The major risk involved in this surgical procedure is infection at the joint. It has been found that for less than 1% of patients  this complication arises. Another complication found in up to 155 of the patients is called Deep vein thrombosis. Of these, around 2 to 3 % are symptomatic.  1 to 2 % of patients have been found to get nerve injuries while stiffness or persistent pain occurs in 8 to 23 % of the patients. 5 years after the surgery, about 2% of the patients may get prosthesis failure as well.

Deep vein thrombosis

Deep vein thrombosis in the leg is a very common complication in knee replacement surgery. The prevention of this may include the periodic evaluation of the legs, doing lower leg exercises to improve circulation and using support stockings and medication to thin the blood.


Periprosthetic fractures are becoming more frequent with the osteoporotic bones in aging patient population and can occur intraoperatively or postoperatively. Most of them need surgery.

Stiff knee

The knee at times may not recover its normal range of motion (0–135 degrees usually) after total knee replacement. Much of this depends on pre-operative function but most patients can achieve 0–110 degrees. However, stiffness of the joint can occur and in some situations the manipulations of the knee under anaesthetic is used to reduce the stiffness. There are manufacturers who have produced implants that are designed for high-flex knees.  These implants offer a greater range of motions.


Instabilities can occur early due to the injured ligaments or later due to the loosening of the implant components over time to wear and tear.  With improvement in medical technology, the risk has fallen considerably. Today these implants can stay for up to 20 years.


Though relatively rare, the periprosthetic infection is one of the most challenging complications in joint replacement. No laboratory test has the 100% sensitivity that can detect the infection early. The specificity of the tests improve when they are performed in patients with clinical suspicion. The CRP and ESR are good tests to screen with high sensitivity and low specificity. The aspiration of the joint remains the test with highest specificity in detecting and confirming infections.

The choice of treatment depends on the type of prosthetic infection.

  1.  Positive intraoperative cultures: Antibiotic therapy alone
  2. Early post-operative infections: antibiotics, debridement and retention of prosthesis.
  3. Acute hematogenous infections: antibiotic therapy, debridement, retention of prosthesis.
  4. Late chronic: delayed exchange arthroplasty. Parenteral antibiotics and Surgical débridement alone in this group has limited success with standards of care involving exchange anthroplasty.

Knee replacements are now being used in younger paople as welll since they last much longer. If they wear out, the surgery to fix the replacement is a much smaller and still effective surgery.

Recent Advances

Have taken place primarily in the direction of enhancing the life of the replaced joint. Apart from improvement in materials and instrumentation, computer help has also been seeked.Computer navigation systems have been developed to facilitate ideal placement of implants. Disadvantages includes expensive system, prolonged operative time and hence the exposure.

Conventional instruments require medullary access to femur bone which may not be possible in all cases. To circumvent such problems, patient specific instrumentation system has been developed. Here based on patient,s local anatomy, cutting blocks are customised. They can be used in regular cases also for the sake of improved outcomes in terms of implant positioning

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61 yrs old foreign national with severe loss of mobility with pain. Underwent both knees replacement surgery together and was able to fly back to her country after 2 week

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62 yrs old Indian lady with single knee joint arthritis. Was sent back home within 2 days and stick mobilisation in a week’s time.

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70 yrs old female who perhaps waited too long for the surgery. Total destruction of joint has taken place as she kept on loading the diseased joint. Surgery becomes tricky and postop rehabilitation go on for months.

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Single joint involvement where osteoarthritis was perhaps precipitated by crystal deposition disease (pseudogout) and acl deficiency.

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Elderly foreign national with failed replaced joint one side. Managed successfully with special implants.

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