Eccentric Exercises in patellar tendinopathy.

A comparison of decline eccentric squats to standard eccentric squats:
Kongsgaard M et al in a recent study have shown excellent clinical results using eccentric squat training on a 25 degrees decline board to treat patellar tendinopathy.
To explore why therapeutic management of patellar tendinopathy using decline eccentric squats offer superior clinical efficacy compared to standard horizontal eccentric squats, their study compared EMG activity, patellar tendon strain and joint angle kinematics during standard and decline eccentric squats. This study suggested the use of a 25 degrees decline board increases the load and the strain of the patellar tendon during unilateral eccentric squats.

See the following URL for single leg eccentric exercise of Quads on a declining plane:
http://www.youtube.com/watch?v=wY98htXP0O4. Now when you have seen watching the video we will go through current researches on the topic.

Single-limb squats on a decline angle have been suggested as a rehabilitative intervention to target the knee extensors especially the single-leg squat on a 25 degrees decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. However, differences in mechanical loading of the patellar tendon have been suggested as a reason for varying effects in rehabilitation of patellar tendinopathy using different eccentric squat exercises and devices.
The key thing is that several assumptions have been made about eccentric exercise’s working mechanism on patellar load and patellofemoral forces, but these are not substantiated by biomechanical evaluations. Investigators have not presented with any empirical research in which they have documented the biomechanics of these exercises or have determined the optimum angle of decline used.
How ever the following may be helpful for your clear understanding:
1. Frohm A et working on patellar tendon load in different types of eccentric squats demonstrated clear differences in the biomechanical loading on the knee during different squat exercises. Quantification of such differences provides information that could be used to explain differences in rehabilitation effects as well as in designing more optimal rehabilitation exercises for patellar tendinopathy.
2. Zwerver J et al investigating on biomechanical analysis of the single-leg decline squat found single-leg squats at decline angles more than 15 degrees result in 40% increase in maximum patellar tendon force. In knee flexions more than 60 degrees, patellofemoral forces increase more than patellar tendon forces. They further suggested higher tendon load can be achieved by the use of a backpack with extra weight.
3. In a biomechanical investigation of a single-limb squat on declining angle Richards J et al found; as the decline angle increased, the knee extensor moment and EMG activity increased. As the decline angle increased, the ankle plantar-flexor moments decreased; however, an increase in the EMG activity was seen with the 24 degrees decline angle compared with the 16 degrees decline angle. This indicates that decline squats at an angle greater than 16 degrees may not reduce passive calf tension, as was suggested previously, and may provide no mechanical advantage for the knee.

Surgical treatment compared with eccentric training for patellar tendinopathy: Evidences from RCTs
There are reports of superior clinical efficacy of decline eccentric squats in the rehabilitative management of patellar tendinopathy. Although the surgical treatment of patellar tendinopathy (jumper's knee) is a common procedure, there have been no randomized, controlled trials comparing this treatment with forms of nonoperative treatment.

Bahr R et al compared the outcome of open patellar tenotomy with that of eccentric strength training in patients with patellar tendinopathy. 40 knees who had been referred for the treatment of grade-IIIB patellar tendinopathy were randomized to surgical treatment (twenty knees) or eccentric strength training (twenty knees).
The eccentric training group performed squats on a 25 degrees decline board as a home exercise program (with three sets of fifteen repetitions being performed twice daily) for a twelve-week intervention period.
In the surgical treatment group, the abnormal tissue was removed by means of a wedge-shaped full-thickness excision, followed by a structured rehabilitation program with gradual progression to eccentric training. The primary outcome measure was the VISA (Victorian Institute of Sport Assessment) score (possible range, 0 to 100), which was calculated on the basis of answers to a symptom-based questionnaire that was developed specifically for patellar tendinopathy. The patients were evaluated after three, six, and twelve months of follow-up.

No advantage was demonstrated for surgical treatment compared with eccentric strength training. Eccentric training should be tried for twelve weeks before open tenotomy is considered for the treatment of patellar tendinopathy.