What Is the Patellofemoral Joint of the Knee?

Anatomy of the knee joint and its surrounding bones and muscles.
Anatomy of the knee joint and its surrounding bones and muscles. SCIEPRO/Getty Images

Definition of the Patellofemoral Joint

Anatomically, there are three compartments in the knee. Where the femur (thigh bone) meets the tibia (large shin bone), there is an inner (medial) and outer (lateral) compartment. The third compartment, formed by the patella (kneecap) and femur, is known as the patellofemoral joint. When you sing "the knee bone's connected to the thigh bone" you are singing about the patellofemoral joint.

The patella, or kneecap, is in the front of your knee and it is the connection point for the muscles of the front of your thigh, the quadriceps, with the tibia shin bone. The underside of the patella rests in the trochlear groove that is on the top of the femur where it meets it in the knee. These bones are covered by articular cartilage, which provides the smooth-gliding surface needed for the joint to function well.

  • Pronunciation: puh-tella-fem-or-uhl
  • Alternate Spelling: patello-femoral joint

What Does the Patellofemoral Joint Do?

The patellofemoral compartment of the knee gets the most use when you walk on an incline, going uphill or downhill. It also is involved with the movement of going up and down stairs. When you kneel or squat or get up out of a chair you are moving the patellofemoral joint. Pain associated specifically with any of those motions may be due to patellofemoral arthritis.

The patellofemoral joint is affected by the alignment and rotation of the femur and tibia and pelvic position and strength. If any of those have an imbalance, it can affect the joint function. The patellofemoral joint is acted upon by ligaments, muscles and nerves that work together to allow joint motion and stability.

The ligaments of the knee include the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament. The medial meniscus and the lateral meniscus are cartilage pads between the femur and the tibia. Fluid-filled bursa sacs surround the knee joint. The bones of the knee are lined with cartilage to provide a smooth gliding surface. The quadriceps muscles extend the knee while the hamstring muscles flex it.

Patellofemoral Arthritis

Knee osteoarthritis can affect any or all of the knee compartments. It develops in the patellofemoral joint when the articular cartilage of the patella is damaged, degenerated or lost. In a normal knee, the cartilage covers the bones to provide a smooth gliding surface.. When it degenerates, inflammation and bony spurs can develop and eventually a bone-on-bone condition can occur. It is seen in as many as 79% of people over age 65.

Partial Knee Replacement for the Patellofemoral Compartment

A total knee replacement is often performed when osteoarthritis affects all three knee compartments. If only the patellofemoral compartment is affected, a partial knee replacement is an option. It replaces only the cartilage under the kneecap.

In a patellofemoral knee replacement, prosthetic components are placed on the femur and patella after resurfacing them to remove the degraded cartilage and smooth the bone. These prosthetic components are made of metal and plastic and are placed on the bone similarly to capping a tooth. In this type of partial knee replacement, the bones and ligaments are left intact. The implants include a plastic disc on the undersurface of the kneecap and a metal groove on the end of the femur. They are held in place by bone cement.

More: Patellofemoral Replacement


Young-Mo Kim, MD, PhD, Yong-Bum Joo, MD, PhD. "Patellofemoral Osteoarthritis," Knee Surg Relat Res. 2012 Dec; 24(4): 193-200.

Patellofemoral Arthritis, American Academy of Orthopaedic Surgeons, March, 2011.

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