Low Range of Ankle Dorsiflexion Predisposes for Patellar Tendinopathy in Junior Elite Basketball Players: A 1-Year Prospective Study.
Backman LJ, Danielson P.  Am J Sports Med. 2011 Sep 14. [Epub ahead of print]
Patellar tendinopathy is one of the most common causes of knee pain in sports; especially those involving rapid jumping like volleyball and basketball. Unfortunately, the causes of patellar tendinopathy remain unclear. Many factors have been hypothesized to increase the risk of developing patellar tendinopathy: intensity of training, training surface, strength, flexibility, poor landing technique, etc. A recent study demonstrated that athletes with patellar tendinopathy had less ankle dorsiflexion but it was unclear if limited dorsiflexion causes patellar tendinopathy or if it was a consequence of the patellar tendinopathy. To determine if limited ankle dorsiflexion contributed to the onset of patellar tendinopathy, Backman et al conducted a 1-year prospective study to examine if reduced ankle dorsiflexion range of motion increases the risk of developing patellar tendinopathy among 75 Swedish junior elite basketball players. The included basketball players had no history of anterior cruciate ligament reconstruction, Osgood-Schlatter disease, femoropatellar cartilage injury, and no signs of anterior knee pain at baseline. Ankle dorsiflexion range of motion was measured with an inclinometer on the tibia during a standardized weight-bearing lunge following a warm-up at both baseline, and at 1-year follow-up. Athletes that developed knee symptoms during the year were evaluated using a standardized clinical definition for patellar tendinopathy. At one year, no athletes developed bilateral patellar tendinopathy, and 12 athletes had developed unilateral patellar tendinopathy. Those 12 athletes with patellar tendinopathy at follow-up, had significantly less dorsiflexion at baseline compared to the athletes that did not develop patellar tendinopathy. Athletes with dorsiflexion less than 36.5 degrees had a 18.5 to 29.4% risk of developing patellar tendinopathy compared to a 1.8 to 2.1% risk for athletes with dorsiflexion greater than 36.5 degrees.
This study provides further evidence that limited dorsiflexion is a risk factor for developing patellar tendinopathy. While the authors proposed a cutoff of 36.5 degrees of dorsiflexion during a lunge, based on statistical analyses, it is important for this cutoff to be confirmed in another cohort. Limited dorsiflexion may be important because it is impairing the athletes’ ability to dissipate forces causing the patellar tendon to experience greater loads. Injuries can occur with a single high-force impact or, as in patellar tendinopathy, a highly repetitive low-force exposure with inadequate time for the tissue to recover. This study complements two other studies that showed that increases tightness of the hamstrings and quadriceps also contributes to development of patellar tendinopathy and anterior knee pain. An important next step would be to see if we can reduce the risk of developing patellar tendinopathy by increasing dorsiflexion and decreasing tightness of the hamstring as well as quadriceps. Regardless, stretching and range of motion exercises are relatively low risk, have other benefits, and may be worth incorporating into our injury prevention programs while we wait for further verification of their benefit at reducing the risk of patellar tendinopathy.
Written by: Jeffrey B Driban
Reviewed by: Kyle Harris

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Backman LJ, & Danielson P (2011). Low Range of Ankle Dorsiflexion Predisposes for Patellar Tendinopathy in Junior Elite Basketball Players: A 1-Year Prospective Study. The American journal of sports medicine PMID: 21917610