Knee injuries are relatively common in tennis, comprising about one fifth of all tennis injuries. The most common injuries are meniscus injuries and degenerative cartilage problems in middle aged and elderly recreational players. In younger individuals, patellofemoral pain syndromes are the most frequent and intriguing problems. Knee overuse syndromes occur more commonly on surfaces such as all weather concrete because they are more fatiguing and have higher friction than clay surfaces do.