Central Importance of the Patella
Leg bones carry the weight of the body. The thigh bone (aka the “femur”), shinbone (aka the “tibia”), and calf bone (aka the “fibula”) convey the body’s weight with each step we take with the help of the kneecap (aka “patella”).
An Interlocking System
Our skeletal system of individual bones is linked by ligaments, muscles, and cartilage. When we walk, our body weight is transferred through the thigh bone, also known as longest bone in the body and strongest bone in the leg. When this bone fails, it often has no effect on the function of lower leg bones. Femoral fractures most often occur in the central portion of the thigh bone called the “femoral shaft”, and do not directly impact the kneecap. The kneecap “facilitates” the weight transfer from the thigh bone to the shinbone and calf bone, the second strongest bone in the weight-bearing leg’s structure and the thinnest bone in the mechanism, respectively. They transfer weight to the ankle. Tibial shaft fractures are the body's most common broken bones, perhaps related to their weight-bearing in the lower leg. Less common fibular fractures do not transfer weight in walking.
The kneecap covers and protects the front of the knee joint. It approximates the bottom of the thigh bone in a shallow trough and the shinbone at the “tibial plateau” at the top end of the shinbone. Both bones are protected by flexible cartilaginous tissue in the trough and plateau areas, permitting the bending motion at the knee. The three bones are held in place and ligament alignment by the “collaterals” (lateral and medial) and the “cruciates” (anterior and posterior). The kneecap position is maintained by additional tendons, the “quadriceps” and “patellar”. With injury at the bone insertions of the patellar and tibial tendons or with kneecap dislocation, walking will be compromised or limited. Unfortunately, injuries to these structures are common with contact athletics.
When the tendon support structures fail to hold the kneecap in place, the knee joint fails. The medical term is “patellar dislocation”. The etiology is rather specific, either trauma directly to the knee from body or sports equipment contact or from a twisting motion occurring at the knee level (accompanied by inability to stand on the involved leg). The kneecap may be visibly in the wrong place, e.g., the side of the leg instead of the front, or there may be a lack of mobility. Pain may radiate from the front of the knee with activity or be present even at rest. Stiffness, joint noise like creaking and crackling, may be present and accompanied by swelling.
Troubleshooting a bad knee will require physical examination with x-ray and MRI imaging to define the problem and differentiate ligament tears from stretches or bone damage, visit Orthopaedic Specialist to get immediate treatment. Ligament damage may require surgical or arthroscopic reconstruction. Rehabilitation of repaired structures or for strengthening minimally damaged dislocations may be indicated. Even flaccid tissues anchoring the kneecap may benefit from physical therapy.