102 water polo players were interviewd about the injuries caused by water polo. 13% of the subjects had knee pain at least once a year. 73% of which were chronic cases. For 24 players, clinical examinations, including X-ray examination, A-P knee laxity measurement, isokinetic strength measurement of knee muscles, and photo analysis of the vertical egg beater kick motion were performed to elucidate the cause of knee pain.
The summary of the results were as follows;
1. The most common site of knee pain was the medial portion of the knee joint.
2. Protrusion of the medial femoral epicondyle and sharpning of the tibial intercondylar eminentia as well as spur formation of the superior pole of the patella were observed in most subjects.
3. Injured subjects had stiff knees and weak knee extensor muscles.
4. The vertical egg beater kick motion must be the main factor of the painful knee.

102 water polo players were interviewd about the injuries caused by water polo. 13% of the subjects had knee pain at least once a year. 73% of which were chronic cases. For 24 players, clinical examinations, including X-ray examination, A-P knee laxity measurement, isokinetic strength measurement of knee muscles, and photo analysis of the vertical egg beater kick motion were performed to elucidate the cause of knee pain.
The summary of the results were as follows;
1. The most common site of knee pain was the medial portion of the knee joint.
2. Protrusion of the medial femoral epicondyle and sharpning of the tibial intercondylar eminentia as well as spur formation of the superior pole of the patella were observed in most subjects.
3. Injured subjects had stiff knees and weak knee extensor muscles.
4. The vertical egg beater kick motion must be the main factor of the painful knee.