The integrity of the knee depends on the healthy function and stability of the confluence of bones, cartilage and ligaments that comprise this weight-bearing joint. The combined actions of weight bearing and bending place significant stress on the knee. Injuries to the knee cartilage, ligaments or bones provoke pain and typically limit joint function.
Meniscal Tear
The meniscus is a cartilage cushion between the upper leg bone, the femur, and the large lower leg bone, the tibia. Sudden, forceful twisting of the knee or a direct blow can cause a meniscal tear. Among older adults with pre-existing degeneration of the cartilage, a meniscal tear can occur with minor trauma. The American Academy of Orthopaedic Surgeons reports that meniscal tears are among the most common knee injuries. Typical symptoms include knee pain, swelling, joint stiffness, limited capacity to fully bend and extend the knee, and feeling that the knee becomes "stuck" or gives way. Notably, a meniscal tear generally does not interfere with walking. Minor meniscal tears may heal with rest. Significant tears require surgical repair.
Anterior Cruciate Ligament Injury
Ligaments are fibrous bands of tissue that hold the bones in place. Four ligaments hold the bones of the knee joint in alignment, including the anterior cruciate ligament, or ACL. The University of Maryland Medical Center explains that the ACL runs diagonally across the front, middle area of the knee. Together with the posterior cruciate ligament, the ACL facilitates bending and straightening of the knee. The ACL also provides support for knee twisting. Common mechanisms of ACL injury include sudden stops or changes in direction while walking or running, off-balance landing while jumping and direct blows to the knee. ACL injuries range from mild sprains to complete tears. Symptoms of ACL injury include pain, swelling, tenderness, limited knee motion and difficulty walking. With complete ACL tears, the knee joint is noticeably loose. Minor stretching of the ACL may respond to bracing and rest. Partial or complete ACL tears require surgical repair.
Patellar Fracture
The patella, or kneecap, acts as a bony shield for the knee joint. It also serves as a point of attachment for the thigh muscles of the front of the leg. Patellar fractures typically occur due to a direct blow to the front of the knee. High-force impacts may shatter the patella into several pieces. Symptoms of patellar fractures typically include swelling over the kneecap, severe pain, bruising and inability to walk or straighten the knee. The American Academy of Orthopaedic Surgeons notes that most patellar fractures require surgery to hold the bone together, facilitating healing. Typically, no weight bearing can occur during the bone healing process. Rehabilitation proves important with patellar fractures.
References
- American Academy of Orthopaedic Surgeons: Meniscal Tears
- American Academy of Orthopaedic Surgeons: Anterior Cruciate Ligament Injuries
- University of Maryland Medical Center: Anterior Cruciate Ligament (ACL) Injury
- American Academy of Orthopaedic Surgeons: Patellar (Kneecap) Fractures
- University of Pittsburgh Medical Center: Patella Fracture
