Keith Weinhold, PT
Fremont Health Medical Center Sports Medicine Clinical Coordinator
Most sports involve some degree of jumping, and during landing, the athlete is at a high risk for injury - especially at the knee. During landing, high amounts of force are absorbed through the lower extremities, and incorrect performance can cause severe derangement, or disruption of the normal functioning of the ligament or cartilages, of the knee structure. According to research, 70% of all anterior cruciate ligament (ACL) injuries occur when landing from a jump.
During the landing phase, forces of nearly five times your body weight may be experienced. A proper landing technique allows for the anterior thigh muscles (quadriceps) and the calf muscles (gastrocnemius) to cushion the body from shock. Severe knee injury occurs when the body does not absorb theses forces.
For example, an awkward landing on one leg with the hip rotated inwards, knee straight, with the force from the landing pushing the knee inward, does not allow the muscles of the legs to alleviate the increased force. A landing on both feet with the knees moving into a "knock-kneed" position is equally as risky. Landing on the forefoot, versus a heel to toe technique, increases difficulty for the body to successfully disperse force.
Research has shown females are more likely to perform landings with decreased musculature use and increased ligamentous dependence. Females are up to six times more likely to tear an ACL as compared to males.
Muscle balance between the quadriceps and hamstrings (posterior thigh muscles) also provides knee stability during jumping and landing. The hamstrings are the backup stabilizer of the ACL. A greater dependence on the quadriceps means more dependence on the ligaments to prevent the tibia (lower leg bone) from shearing forward with respect to the femur (upper leg bone.)
Another risk factor for knee injury is asymmetrical muscular use between the right and left legs. An athlete that tends to land more on one leg will accept an increased load through that particular knee.
With the cost of ACL reconstruction and rehabilitation for female high school basketball players alone estimated at $119 million annually, at an average cost of $17,000 per case, focus on injury prevention is essential. Training for the promotion of proper landing technique and strength training is the most effective and practical way of preventing jump-related injuries. A study by T.E. Hewett in 1996 demonstrated maximum landing forces during a volleyball block were decreased by 22% after 6 weeks of plyometric training. Forces acting inwards and outwards on the knee were reduced by 50%.
Strength training should consist of general lower extremity exercises for power and endurance. Special attention should be paid to the quadriceps for cushioning during landing and the hamstrings for dynamic stability of the knee. Core strengthening is required for maintenance of a stable base for the extremities. Flexibility of the legs allows for the hip, knee, and ankle to move through the appropriate range of motion for force dissipation during landing. Dynamic strength should include plyometric strengthening, which is exercise requiring quick, abrupt changes in movement direction while maintaining neuromuscular control of the body.
Landing technique is extremely important, as researchers have observed the height of the jump is less important than knee angle in predicting the magnitude of force through the lower extremity. Training should emphasize landing with the knees bent and aligned forward to allow the quadriceps and calf musculature to absorb the landing. Both legs should accept weight equally. A heel to toe landing technique should be used versus a forefoot landing. Videotaping and performing jumping in front of a mirror allow for visual feedback of current preferred strategies and for performance of proper landing strategies.
Knee injuries are associated with more time lost from sports participation than any other part of the body. Jumping and cutting sports exhibit the highest risk for knee injury. With conditioning, strength training, and technique instruction, millions of dollars can be saved and less loss of time from sport can be attained. Talk to your athletic trainer or a physical therapist for more information.
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