The patella, or kneecap, is a small, triangular bone at the front of the knee joint. It is the body’s largest sesamoid bone, embedded within the quadriceps tendon. Its primary role is to enhance the quadriceps muscle’s efficiency, allowing it to straighten the knee more effectively. The patella also protects the knee joint and maintains alignment by gliding within a groove on the thigh bone (femur).
While total knee replacement is common, the patella itself can be replaced. This can occur as part of a total knee replacement or as a specific procedure for damage limited to the kneecap and its corresponding groove on the femur, known as patellofemoral arthroplasty. This targeted approach addresses damage in only one area of the knee, preserving healthy joint portions.
When Patella Replacement is Considered
Patella replacement surgery is considered when medical conditions primarily affect the patellofemoral joint, leading to significant pain and functional limitations. This procedure is recommended after non-surgical treatments have been exhausted without adequate relief. The most common reason is severe osteoarthritis largely confined to the patellofemoral compartment, the area between the kneecap and thigh bone.
This arthritis results from cartilage wear on the patella’s underside and within the femur’s trochlear groove. Post-traumatic arthritis, developing after a patella injury, is another condition. Patients often experience pain behind the kneecap, especially during activities like climbing stairs, sitting with bent knees, or rising from a chair.
Patellofemoral arthroplasty is a less common procedure than total knee replacement. The ideal candidate has arthritis localized only to this front part of the knee, with the other two compartments remaining healthy. Patient selection is important, as the procedure is most successful when damage is limited to this specific area.
The Patella Replacement Procedure
Patellofemoral arthroplasty involves resurfacing the damaged surfaces of the kneecap and thigh bone. A surgeon makes an incision at the front of the knee to access the joint. During the procedure, damaged cartilage and a small amount of underlying bone are precisely removed from the patella’s underside.
A plastic implant is then secured to the prepared underside of the kneecap. If the corresponding trochlear groove on the femur is also damaged, a thin metal component resurfaces it. These implants are typically secured to the bone using cement.
This surgical approach replaces only the affected areas, preserving healthy cartilage, bone, and ligaments in the rest of the knee. In contrast, a total knee replacement resurfaces all three compartments. Patellofemoral replacement is considered a less invasive option, involving a smaller incision and less soft tissue damage.
Recovery and Life After Patella Replacement
Recovery following patella replacement surgery is a gradual process involving careful management and dedicated rehabilitation. Patients are typically allowed to put weight on their knee immediately after surgery, though assistive devices may be necessary for several days or up to six weeks. The initial post-operative period may involve a brief hospital stay, as many procedures are performed on an outpatient basis.
Physical therapy is a fundamental part of the recovery, usually beginning within about a week. These exercises help regain strength in the quadriceps muscles and improve the knee’s range of motion. While some swelling and discomfort are common for several weeks, they are manageable with prescribed medications.
Patients can expect to return to many daily activities and work within 2 to 6 weeks, often a faster timeline than with a total knee replacement. Full recovery can take 6 to 12 months. Expected outcomes include significant pain relief and improved knee function, with many patients reporting the replaced joint feels more natural compared to a total knee replacement. Potential complications can include infection, blood clots, or persistent stiffness.