Swimmer’s Knee

In 1974, researchers conducted a survey on the incidence of injuries to various parts of the musculoskeletal system of swimmers, and noticed that a high percentage of breaststroke swimmers complained of pain in the medial knee. (Kennedy, J. Hawkins, R. Breaststroker's knee. Physician and Sportsmedicine. 1974;2:33-38.)

This condition has been termed breaststroker's knee, although further studies by Vizsoly (et al) on a population of 391 competitive swimmers showed that breaststroker's knee was diagnosed in 56 out of 77 breaststroke swimmers (73 percent), but also in 153 out of 314 swimmers (48 percent) who used either the freestyle, backstroke, or butterfly stroke.(Vizsoly, P. Breaststroker's knee. An analysis of epidemiological and biomechanical factors. American Journal of Sports Medicine. 1987; 15:63-71.)

The condition is primarily seen in breaststrokers because of the whip kick. Much of the speed in the breaststroke comes from the whip kick. Kennedy and Hawkins's initial paper reported that the condition was caused by weakness in the medial collateral ligament, resulting from repeated stretching during breaststroke swimming. In their opinion, the stretching of the ligament was caused by the extension part of the "whip kick," accompanied by an excessive valgus stress on the knee joint and the outward rotation of the leg in the final phase of the stroke.

The medial collateral ligament is the main supporting structure on the medial side of the knee; it is also called the tibial collateral ligament. Tension in the ligament increases as the knee moves from flexion to extension. This is exactly what happens during the kicking motion of the whip kick during breaststroke swimming. All the force is generated right at, directly on, bulls-eye hit to the medial collateral ligament.

Different authors point to different areas on the ligament that are causing the pain, but the main point is that, uniformly the pain-producing structure in breaststroker's knee is a laxity or sprain of the medial collateral ligament.(Stulberg, S. Breaststroker's knee: pathology, etiology, and treatment. American Journal of Sports Medicine. 1980; 8:164-171.-Costill, D. Handbook of Sports Medicine and Science Swimming. Oxford: Blackwell Scientific Publications, 1992.)

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