- Jim G Blount, MD, CAQSM
Jim G Blount, MD, CAQSM
- Adjunct Clinical Professor, Departments of Family Medicine and Sports Medicine
- University of North Carolina at Chapel Hill
The patella is the largest sesamoid bone and serves several important functions. It improves the mechanics of knee extension, protects the knee joint from direct trauma, and assists in providing nourishment for the articular cartilage of the distal femur . Patella fractures account for approximately 1 percent of all skeletal injuries in both adults and children.
This topic will review fractures of the patella. Other injuries of the knee and lower extremity are discussed separately. (See "General evaluation of the adult with knee pain" and "Recognition and initial management of lateral patellar dislocations" and "Proximal tibial fractures in adults" and "Anterior cruciate ligament injury" and "Meniscal injury of the knee" and "Medial collateral ligament injury of the knee".)
Patella and surrounding tissue — The patella is triangular with the apex directed distally (picture 1 and figure 1 and figure 2). The superior pole of the patella serves as the site for the insertion of the quadriceps tendon, which is the confluence of the four individual quadriceps muscle tendons (rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis). The quadriceps tendon envelopes the patella and becomes the patella tendon distally, inserting on the tibial tuberosity. Forces exerted by the quadriceps muscles on the patella (eg, when landing on one's feet after a fall from a moderate height) can lead to indirect fracture and proximal retraction of the superior fracture piece, if there is complete disruption of bone or tendon.
The medial patellar retinaculum is an extension of the vastus medialis tendon that attaches to the superomedial border of the patella and distally to the medial condyle of the tibia. The lateral patellar retinaculum is an extension of the vastus lateralis and attaches to the superolateral border of the patella and distally to the lateral condyle of the tibia. If the medial and lateral retinacula are intact following a patella fracture, the patient may retain the ability to actively extend the knee.
The anastomoses of the superior, middle, and inferior geniculate arteries serve as the primary blood supply to the patella (picture 2). Branches of these arteries enter the bone through the central patella and distal pole. Fractures through the mid-patella can thus compromise blood supply to the superior pole and increase the risk for avascular necrosis . Knee anatomy is discussed in greater detail separately. (See "Physical examination of the knee", section on 'Anatomy'.)
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- CLINICAL ANATOMY
- Patella and surrounding tissue
- Bipartite patella
- MECHANISM OF INJURY AND FRACTURE PATTERN
- CLINICAL PRESENTATION AND EXAMINATION
- RADIOGRAPHIC FINDINGS
- INDICATIONS FOR ORTHOPEDIC REFERRAL
- DIFFERENTIAL DIAGNOSIS
- INITIAL TREATMENT
- FOLLOW-UP CARE
- PEDIATRIC CONSIDERATIONS
- RETURN TO WORK AND SPORTS
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS