WHAT'S NEXT In mint condition, the knee is a biomechanical marvel, an intricately linked interaction of bones, ligaments, tendons and cartilage that produces smooth, stable motion. But as professional athletes and weekend exercisers know only too well, the knee is also a classic weak spot, vulnerable to damage and slow to heal. Strengthening it after injury or surgery may require hours on the bulky machines of a hospital or gym. Now a mechanical engineer at Northeastern University has devised a small portable device that people may be able to strap onto their knees to rehabilitate them as they walk around...
