The Long-term Effects of Unilateral Lower Limb Musculoskeletal Injury on Bone Mineral Density and Isometric Quadriceps Strength

Abstract

Summary Musculoskeletal injuries of the lower limb are commonplace and can lead to long-standing deficits in bone mineral density (BMD) and muscle strength. This may predispose subjects to re-injury and lower their threshold for functional ability. This study aims to investigate the relationship between BMD and peak isometric quadriceps strength and considers whether subsequent strength training is of benefit. Ten subjects (two female) with previous lower limb musculoskeletal injuries were assessed. The BMD in the knee region was measured bilaterally using dual energy X-ray absorptometry (DEXA, model DPX-L). The peak isometric quadriceps strength was assessed using the KinCom 500H isokinetic dynamometer. The injured limb was compared to the uninjured limb (I/UI%). Significant differences were seen between the injured and uninjured limb for BMD in the femur (p = 0.039), tibia (p = 0.014) and in the combined site (p = 0.017); and peak isometric quadriceps strength (p > 0.001). No relationship was found between the decrements in muscle strength and BMD. A further pilot study (n = 6) was conducted to assess the impact of a 12-week home exercise training programme on the BMD and isometric quadriceps strength deficits. These results were encouraging with increases in the quadriceps strength and/or BMD and a statistically significant increase in the load lifted in training.