Unicompartmental vs Tricompartmental Osteoarthritis: What's the Difference
If you have been diagnosed with osteoarthritis of the knee, you may have heard terms like unicompartmental and tricompartmental. At first, these words sound overly medical, and it is not always clear what they mean. But understanding them is important, since the type of arthritis you have can affect your treatment and long-term outlook.
When doctors talk about osteoarthritis type differences, they are often describing how much of the knee joint is affected. Some patients only have damage in one section of the knee, while others experience changes across the entire joint.
In this blog, we will break down what these two types mean, how they impact your mobility, and what treatment choices you may face. By the end, you will feel more confident discussing your diagnosis with your doctor.
Understanding the Basics of Knee Osteoarthritis
To start, let’s look at how knee osteoarthritis develops. The knee is made up of three main compartments, the medial (inner side), lateral (outer side), and patellofemoral (the area under the kneecap). These compartments are lined with cartilage that cushions and protects the bones during movement.
In osteoarthritis, this cartilage begins to wear down. As it thins, the bones rub against each other, causing pain, stiffness, and swelling. Over time, this damage can spread from one compartment to others.
For some people, arthritis stays limited to one area for years. For others, it progresses to multiple compartments, creating greater discomfort and reducing movement. The difference between unicompartmental and tricompartmental osteoarthritis comes down to how widespread the damage is within these compartments.
Therefore, understanding which type you have is not only a label, it is a guide for how doctors may recommend treating it.
What is Unicompartmental Osteoarthritis?
Unicompartmental osteoarthritis, sometimes called partial knee arthritis, affects only one of the three compartments in the knee. Most often, it impacts the medial side, which bears much of the body’s weight.
People with this type may experience pain on one side of the knee, rather than across the entire joint. Swelling and stiffness may be present, but symptoms are generally more localized compared to more advanced arthritis.
Moreover, patients with unicompartmental arthritis often still have good mobility in the rest of the knee. This means activities like walking or climbing stairs may still be possible, although discomfort can increase with use.
Key points about unicompartmental osteoarthritis:
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Pain is usually felt in one area of the knee
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Joint damage is less widespread
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Treatments may include physical therapy, injections, or partial knee replacement
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Patients often maintain better overall movement compared to tricompartmental cases
Therefore, catching osteoarthritis early and identifying if it is confined to one compartment can help preserve more natural knee function over time.
What is Tricompartmental Osteoarthritis?
Tricompartmental osteoarthritis is more advanced, since it affects all three compartments of the knee. This type is sometimes referred to as global knee arthritis. Unlike unicompartmental arthritis, the damage is not localized, making it more difficult to manage with conservative care.
People with this type often experience pain throughout the knee. Stiffness tends to be worse, especially in the morning or after sitting for long periods. In addition, swelling may occur more frequently, and grinding or popping sounds can be felt when moving.
Living with tricompartmental osteoarthritis usually means greater challenges in daily life. Walking longer distances, standing for extended periods, or performing physical work can become difficult.
Some common signs include:
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Pain across the knee rather than in one area
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Severe stiffness, especially after inactivity
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Loss of full range of motion
