PATELLAR TENDON STRAIN IS INCREASED AT THE SITE OF THE JUMPER’S KNEE LESION DURING KNEE FLEXION AND TENDON LOADING: RESULTS AND CADAVERIC TESTING OF A COMPUTATIONAL MODEL. Lavagnino M, Arnoczky SP, Elvin N, Dodds J. American Journal of Sports Medicine

Patellar tendinopathy (jumper’s knee) is characterised by localised tenderness of the patellar tendon at its origin on the inferior pole of the patella. However, it is unclear why the lesion typically occurs in this area of the patellar tendon. Previous surface strain gauge studies of the patellar tendon through the range of motion have produced conflicting results. This study used a computer model developed using anatomical measurements taken from lateral radiographs of a normal knee to gauge the predicted patellar tendon strains that occur

DIFFERENTIAL FORCES WITHIN THE PROXIMAL PATELLAR TENDON AS AN EXPLANATION FOR THE CHARACTERISTIC LESION OF PATELLAR

TENDINOPATHY. Dillon EM, Erasmus

PJ, Müller JH, et al. American Journal of Sports Medicine 2008;36:2119–2127

An optic-fibre technique was used to detect forces in both the anterior and the posterior regions of the proximal patellar tendon in seven healthy subjects. This works on the principle that a longitudinal strain in the tendon or ligament effectively squeezes the optic fibre, which alters the amplitude modulation of transmitted light. Measurements were recorded during the following exercises: closed kinetic chain quadriceps contraction (eccentric and concentric), open kinetic chain quadriceps contraction (eccentric and concentric), a step exercise and a jump exercise.

REGENERATIVE INJECTION OF ELITE ATHLETES WITH CAREER- ALTERING CHRONIC GROIN PAIN WHO FAIL CONSERVATIVE

TREATMENT: A

CONSECUTIVE CASE SERIES. Topol G, Reeves K. American Journal of Physical Medicine and Rehabilitation 2008;87:890–902

Seventy-two athletes (39 rugby, 29 soccer, 4 other) completed the minimum two-

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Results: During all the exercises, the peak differential signal output in the posterior location of the proximal patellar tendon was greater than in the corresponding anterior location. The greatest differential signal output was found in the jump and squat exercises.

sportEX comment

Patellar tendinopathy is a common condition that can result in severe disruption to a sporting career. The Manchester United and England midfielder Owen Hargreaves is one such example. He was written off for the season after playing only a handful of games because of reoccurring patella tendinopathy. These are only very small studies and

treatment protocol. They described a history of groin pain lasting for 3–60 months. The treatment consisted of monthly injections of 12.5% dextrose in 0.5% lidocaine in the abdominal and adductor attachments on the pubis. A total of one to six injections were given. Injection of the nociceptive source was confirmed by repetition of resistive testing 5 minutes after injection. The visual analogue scale of pain with sport (“VAS Pain”) and the Nirschl pain phase scale were measured at 0 months and then at an average of 26 months. Results: There was a VAS Pain improvement of 82% and a Nirschl pain phase scale

therefore they should be treated with care, but in practical terms they suggest that the association of decreasing PPTA with increasing localised tendon strain would implicate the role of knee-joint angle as well as tendon force in the pathogenesis of jumper’s knee. This in turn would suggest that adaptation of technique and training methods may prevent the condition from occurring. The second study, which suggests that the forces are greatest at the posterior portion of the tendon, may account for the varied results in previous studies using surface strain gauge measurements.

as a result of the tendon loads and patella– patellar tendon angles (PPTAs) experienced during a jump landing. PPTAs corresponding to knee flexion angles between 0° and 60° and patellar tendon strains ranging from 5% to 15% were used as input variables in the model. The authors used these data to determine whether the location of increased strain predicted by the computational model could produce isolated tendon fascicle damage in that same area. Five human cadaver patella– patellar tendon–tibia specimens were loaded

under conditions predicted by the model to significantly increase localised tendon strain. Pre- and post-testing ultrasound images of the patella–patellar tendon specimens were obtained in order to document the location of any injured fascicles. Results: Localised tendon strain at the classic location of the jumper’s knee lesion was found to increase in association with an increase in the magnitude of applied patellar tendon strain and a decrease in the PPTA. The principal stresses and strains predicted by the model for this localised area were tensile and not compressive in nature. Applying the tendon strain conditions and PPTA predicted by the model to significantly increase localised strain resulted in disruption of tendon fascicles in three of the five cadaver specimens.

improvement of 78%. Six athletes did not improve following regenerative injection therapy treatment; the remaining 66 returned to unrestricted sport. Return to unrestricted sport occurred in an average of 3 (range 1–5) months.

sportEX comment This study dealt with athletes whose

careers were threatened by injury and who had not responded to conservative physical therapy treatment. The results suggest that, for the vast majority of athletes in the study, the injection of dextrose is a valid treatment of last resort.

sportEX medicine 2009;39(Jan):4-6