Insidious and often undetected until pain and deformity present in latter stages, posterior tibial tendon dysfunction is a common clinical problem and the leading cause of flatfoot deformity in the U.S. adult population. The disorder is associated with age-related degeneration, inflammatory arthritides, hypertension, diabetes mellitus,obesity and, less frequently, acute traumatic rupture.

This progressive debilitating conditionis categorized by four stages (see table).Despite the high prevalence, there are no intervention guidelines for early-stage PTTD. But new clinical research, published in the January issue of Physical Therapy,indicates that patients who are in stages I or II can benefit from a program of orthosis wear and stretching exercises.

Led by Kornelia Kulig, an associate professor of orthopedics at the University of Southern California, the researchers soughtto test the effects of eccentric loading of the tibialis posterior tendon on pain and function in people with tibialis posterior tendinosis. They theorized that a complex exercise program would lead to greater improvements in function and reductions in pain than would be otherwise achieved with a concentric exercise program or the use of arch-correcting orthoses alone.

“We focused on the early stages, where the foot is still flexible and the deformity is already somewhat present but not excessive,’’ Kulig said.

Thirty-six participants who had been experiencing foot and ankle pain for three or more months were recruited from the USC department of orthopedics and Long Beach Memorial Medical Center. All agreed to discontinue athletic activities for the 12-week study period.

All subjects received custom-made orthoses and wore them for 90% of their waking hours. They also all performed stretching exercises.

Participants were randomly assigned to one of three groups: orthosis wear and stretching, orthosis wear, stretching; and instruction in a concentric progressive resistive exercise; and orthoses wear, stretching,and instruction in an eccentric progressive resistive exercise.

All subjects were instructed to perform gastrocnemius and soleus calf muscle stretches two times per day at home, using a lightweight portable slant board. They stretched their calf muscles three times with the knee extended to target the gastrocnemius muscle and three times with the knee slightly flexed to more selectively isolate thes oleus muscle.

The progressive resistive exercises consisted of isolated loading of the tibialis posterior musculotendinous unit (horizontal adduction with plantar flexion). The regimen was performed with the TibPostLoader, a specialized exercise unit that was adjusted to progressively load the tendon either concentrically or eccentrically, depending on the group assignment. A series of three sets of 15 repetitions was performed twice daily. Participants exercised while wearing both orthoses and shoes.

Special springs affixed to the loader provided constant resistance through the range of elongations starting with 0.9 kg (2 pounds) and increasing in at least 0.9-kg increments on the basis of each participant’s ability to perform 15 repetitions.Once the participant was able to perform 15 repetitions in three sets,a new 15-repetition maximum was established.

Participants self-reported a 100% adherence rate for wearing orthoses in their shoes. Adherence to twice-daily stretching and resistive exercise averaged 68%.

The study’s primary outcome measures were the Foot Functional Index (a self-reported measure of pain, function, and activity level)and the five-minute walk test. Patients’ pain levels immediately fol-lowing the walk test were collected before and after the intervention.After the 12-week program, FFI scores (total, pain, and disability)decreased in all groups. Mean FFI total scores significantly decreased,from 30.0 (17.7) before the intervention to 11.5 (12.8) after the intervention (P < .0001).

The group that performed the eccentric exercises demonstrated the most improvement in each FFI subcategory, and the one that used orthoses and stretching alone demonstrated the least improvement. Pain immediately after the walk test was significantly reduced across all groups.

At the six-month follow-up, Kulig reported that the participants were feeling better and experiencing less pain after walking.

Participation in the exercise program did not result in an increase in symptoms. The findings suggest that both concentric training and eccentric training, when performed within the limits of a patient’s pain tolerance, are safe methods for loading the tendon.

Although the group that received eccentric progressive resistive exercise tolerated greater loading after the intervention, researchers said future studies are needed. In those, subjects should begin with equal baseline scores on the primary measures to determine whether eccentric exercise is superior to concentric exercise.

The researchers concluded that the development of an exercise program that strengthens the weakened tibialis posterior musculo-tendinous complex is essential for effectively managing the early stages of PTTD and preventing further degeneration.

Despite the promising outcomes among the study subjects, potential secondary changes in the patients may still occur, according to Kulig and her colleagues.

“Clinically, the patients present better immediately, and six months after, but is tendon structure really changing?’’ she asked.“The tendon does not function in isolation.’’

The researchers also pointed out that there are no specific guidelines as to how to most effectively strengthen the muscle in the presence of painful tendon dysfunction. Interestingly, none of the participants reported pain in the tendon even when the load was at the level of the participant’s maximum ability to resist the movement of the loaded footplate.

Also, the specific interventions used in the trial would not be of any help for patients in stages II or III PTTD, according to Kulig.

“If the tendon is attenuated or there are signs of change in the hindfoot or midfoot, surgery is the only solution,” she said.