Many conditions can cause pain when bending the knee after a fall. According to the American Academy of Family Physicians, acute knee trauma, such as a blow to the knee during a fall, accounts for approximately 1.3 million emergency room visits in the United States each year. Blunt-force trauma to the knee can cause considerable pain, along with decreased pain-free knee joint active range of motion.
Chondromalacia Patellae
Chondromalacia patellae can cause pain when bending the knee after a fall. According to the Sports Injury Clinic website, chondromalacia patellae occurs when the cartilage covering the back of the patella or kneecap is damaged. In a normal, healthy individual, the articular cartilage on the back of the kneecap helps the knee move smoothly and without pain. The Sports Injury Clinic website states that chondromalacia patellae can be caused by acute injuries or long-term injuries. Acute injuries, such as a direct fall onto the kneecap, may cause small tears or roughening of the cartilage. Common signs and symptoms associated with chondromalacia patellae include pain at the front of the knee that's worse with knee movement or when descending stairs, a grinding or clicking sensation with knee bending or straightening, tenderness when the kneecap is pressed, and a small amount of swelling in the affected area.
Dislocated Patella
A dislocated patella can cause pain when bending the knee after a fall. The Children's Hospital Boston states that a dislocated patella occurs when the patella slides out of its usual position on the front of the knee. The most common causes of a dislocated patella include blunt-force trauma, such as a fall on the knee, or a developmental abnormality that leads to improper alignment and tracking of the kneecap over the femur or thighbone. In some cases, a family history of knee instability leading to dislocation may contribute to a dislocated patella. Common signs and symptoms associated with a dislocated patella include pain in the front of the knee that's worse with activity and knee bending, swelling and stiffness in the affected area, a kneecap that slides to one side of the knee, bruising, redness and tenderness at the injury site, and creaking sounds in the knee during knee movement. According to the Children's Hospital Boston, most kneecap dislocations occur in active teenagers and young adults.
Fractured Patella
A fractured patella can cause pain when bending the knee after a fall. According to the Cedars-Sinai Medical Center or CSMC, the kneecap can fracture or break in many different ways, including a partial fracture, a total fracture or a fracture involving multiple pieces of the patella. CSMC states that many patella fractures are accompanied by tendon and ligament damage, such as strains and sprains. Common signs and symptoms associated with a fractured patella include extreme pain in and around the kneecap that's made worse when bending or straightening the knee, swelling in the affected area, difficulty performing a straight-leg raise, an observable kneecap deformity, and tenderness when pressing the kneecap. According to CSMC, patella fractures account for about 1 percent of all injuries to the skeletal system. Most patella fractures occur in individuals between the ages of 20 and 50.
