Health related question in topics Conditions Illness .We found some answers as below for this question How long does it take to heal a broken knee,you can compare them. The time it takes to heal a broken knee depends on the severity of the injury. On average, it takes around 4 to 6 weeks.[ Source: http://www.chacha.com/question/how-long-does-it-take-to-heal-a-broken-knee ].More Answers to  How long does it take to heal a broken knee .ow long does it take a knee sprain to heal? Q: 2 Months 2 weeks ago, I went to the ER for severe knee pain and I was told that I had classic symptoms of a meniscus (sp) tear.