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Knee Replacement Updates - Part 3 of 3

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Jan 26, 2015

Dr. Mackarey's Health & Exercise ForumKnee Replacement Updates - Part 3 of 3

Getting a new knee doesn’t quite mean what it used to.

In younger, active patients — from about age 50 to 65 — having knee problems often means only one of the knee’s three compartments is degenerated. In the past, these patients relied on multiple conservative measures — steroid injections, for example, or oral medication — to tide them over for a few years until the degenerative arthritis advanced to the other compartments of the knee. Then, a total joint replacement — all three compartments — was performed.

Thanks to advances in technology, implant materials and surgical technique, people of all ages with arthritis and degeneration in only one compartment are eligible for a partial knee replacement, also called a hemiarthroplasty or unicompartmental knee arthroplasty (UKA). The benefits are many: shorter hospital stays, less blood loss, more aggressive rehab. And because UKA surgery maintains the ligaments and has less bone loss in the knee than a total replacement, the new knee moves in a more natural manner, which allows quicker return to more aggressive activities.

There also are benefits for older, less medically stable or overweight patients: less pain, less time in the hospital, quicker rehab. That results in fewer infections, blood clots and other complications, even though these patients often start off with other medical conditions.

Total Knee Replacement (TKA)

By surgically replacing the arthritic ends of bones with metal and plastic components, a knee replacement creates new surfaces to allow a joint to function like a natural knee without the pain and restriction of a damaged, degenerative, arthritic knee.

A total knee arthroplasty (TKA) resurfaces all three compartments of the knee joint while trying to preserve most of the surrounding, supporting soft tissues. A TKA is required if cartilage — the thick cushion covering the ends of bones — in all three compartments is damaged or worn away, resulting in arthritis.

For those with arthritis and degeneration in only one compartment — usually the medial or inside compartment — a partial knee replacement may be a better choice. It’s also a less invasive procedure with fewer medical complications.

Partial Knee Replacement (UKA)

UKA was first presented as a surgical option for the treatment of arthritis in the inner compartment of the knee in the 1950s. The idea is to replace as little of the joint as necessary, preserving much of the natural knee anatomy. It was thought that with less bone loss, when the unicompartmental implant wore down, it would be much easier to graduate to a total knee replacement years later. Even then, it was recognized that a total replacement would eventually deteriorate and require a revision — and the revision surgery would be complicated by the loss of bone and soft tissue, rendering the second replacement potentially less effective than the first.

The early UKAs had limited success, due in part to problems with implant and material design, patient selection, limited technology and surgical techniques. Fortunately, that has changed for the better.

Unicompartmental design

According to the American Academy of Orthopaedic Surgeons, a UKA is an option for a select group of patients with osteoarthritis of the knee limited to one compartment. Only the damaged compartment is replaced, with a metal and plastic implant; the healthy, unaffected compartments remain untouched.

Most qualifications for a UKA are the same as for a total replacement — age, weight and medical health are not necessary criteria. But there are some unique criteria to determine if you qualify:

  • Bone-on-bone damage limited to the inner compartment of the knee.
  • No damage to the other compartments.
  • An intact anterior cruciate ligament.
  • A correctable deformity of the knee.
  • Advantages of UKA

When appropriate patients are selected and proper surgical technique performed, several studies have determined that the UKA is a viable and successful option. One study found that as many as 92 percent of UKA patients had excellent or good outcomes, with patients generally reporting a more natural and quieter knee.

Advantages identified in other studies include:

  • Shorter operative time.
  • Fewer blood clots.
  • Quicker recovery and return to more aggressive activities.
  • Less post-op pain.
  • Less blood loss.
  • Shorter hospital stay/less cost.
  • More natural feel and sound.
  • Smaller incision.
  • More aggressive rehab.
  • Quicker and greater return of range of motion.
  • Fewer complications with a revision.

Complications Associated with Partial Knee Replacement

While less frequent, UKA complications are similar to those found with total replacement. They include blood clots, infection, implant wear or loosening, and degeneration of other knee compartments. But there is one risk specifically associated with a UKA: The effect of pain relievers is slightly less predictable.

While the idea of getting a knee replacement — partial or total — is intimidating, it actually is one of the safest and most effective medical procedures. Discuss which option is best for you with an orthopedic surgeon. Northeast Pennsylvania is fortunate to have many highly skilled and experienced board-certified orthopedic surgeons successfully performing knee replacements daily. For more information, and to find out who is performing UKAs in your area, visit the American Academy of Orthopaedic Surgeons website,

Medical Reviewer: HARRY SCHMALTZ, M.D., was medical reviewer for this column. He is an orthopedic surgeon and joint replacement specialist, certified Oxford Unicompartmental Knee replacement surgeon, Scranton Orthopaedic Specialists PC.

PAUL J. MACKAREY, P.T., D.H.Sc., O.C.S., is a doctor in health sciences specializing in orthopedic and sports physical therapy. He is in private practice and an associate professor of clinical medicine at Commonwealth Medical College. His column appears every Monday in the Scranton Times-Tribune. Email: