Knee Fracture
Normal Anatomy
The bones of the knee are the femur (thigh bone), tibia (shin bone) and patella (kneecap). The femur and tibia meet to form the knee joint which is a hinge with the knee cap(patella) in front of these two bones acting as a mobile shield to protect the joint. The patella slides up and down in a groove in the femur called the femoral groove as the knee is bent and straightened.
Ligaments hold the knee together and give it stability. The medial (inner) collateral ligament (MCL) and outer (lateral) collateral ligament (LCL) limit sideways motion of the knee. The posterior and anterior cruciate ligaments (PCL and ACL) limit forward and backward translational motion of the knee bones, keeping them stable and allowing the knee to function as a unit.
Two structures known as menisci sit between the femur and the tibia and act as cushions or shock absorbers for the knee. Menisci are one of two types of cartilage in the knee. The other type, articular cartilage, is a smooth and very slick material that covers the end of the femur, the femoral groove, the top of the tibia and the underside of the patella. This articular cartilage allows the bones to move smoothly without pain. If this layer wears away, it is called arthritis and then the motion becomes painful.
Tendons connect muscles to the bones of the knee. The quadriceps muscles on the front of the thigh are connected to the top of the patella by the quadriceps tendon, which covers the patella and becomes the patellar tendon. The patellar tendon then attaches to the front of the tibia. The hamstring muscles in the back of the leg attach to the leg bone (tibia) at the back of the knee. The quadriceps muscles straighten the knee and the hamstring muscles bend the knee both of which are required for walking, running or simply standing.
Pathology
Knee fractures can occur in young or older patients. These fractures usually occur from a fall in older patients or high-speed injuries such as motor vehicle or motorcycle accidents in younger patients. Knee fractures may involve the lower end of the thigh bone (femur), upper end of the shin bone (tibia), the kneecap (patella), or any combination of the three. X-rays show the breaks, their location and pattern. If the fracture(s) extends into the knee joint, a CT scan may be necessary to learn the true nature and extent of the fracture(s). An MRI may also be necessary to verify whether any ligaments, tendons, or cartilage structures have also been damaged. A physical examination is important to check for injuries to other structures, such as muscles, nerves, ligaments, and/or tendons.
Treatment
Fractures around the knee can be incomplete fractures where the bones do not move out of place. When this is the case, these fractures can be treated in a knee immobilizer and then transition into a brace as range of motion is slowly started. When fractures of the lower end of the thigh bone (femur), upper end of the shin bone (tibia), or kneecap (patella) are complete, if the bones have moved around, and if any of the fractures extend into the knee joint surface, they often require surgery. Surgery ensures that the bone(s) is aligned in the correct position and that the patient will be able to bear weight on the leg once it has been deemed safe by the surgeon. This used to be done with long incisions and plates and screws. Plates and screws may still be required to fix these fractures, but they are now placed through smaller incisions that cause much less damage to the surrounding tissues and the blood supply of the broken bone(s). Special slender metal rods can be placed inside the thigh bone or shin bone through small incisions if necessary. Any ligament, tendon, or cartilage damage that may have occurred may be fixed at the same time as the fracture(s) or at a later date once the fracture(s) has healed. Therapists work with the patient the next day after surgery to start moving the leg, working on strengthening the muscles around the knee and leg, and to begin walking again with weight-bearing restrictions determined by the surgeon. Once the fracture(s) is healed, most patients are able to return to their activities with or without limitations, based on their pre-injury level of ambulation and function.