Heel Today, Rear Tomorrow?: How Achilles Tendinopathy May Affect the Glutes

If your heel hurts, the instinct is to treat the heel. But a growing body of sports-medicine research suggests Achilles tendinopathy rarely acts alone, and that what happens at your hips, especially your glutes, may be part of the story.

Not all Achilles pain is the same. Follow this quick guide to help determine the need for professional evaluation.

If you have any of the following symptoms, please seek immediate first aid:

• A sudden “pop” or snap in the back of the heel while in activity
• A condition in which you are unable to push off or stand up on your toes
• The gap or the deformity in the space above the heel is visible
• Sudden swelling and intense pain

These may be symptoms of a complete rupture of the Achilles tendon which is a surgical emergency requiring immediate evaluation.

If you notice any of these, please make an appointment within 1-2 weeks:

• Slow onset of pain in the heel or tendon which has been present for more than 2 weeks
• Morning and/or rest-related stiffness that is worse than usual
• Running pain that goes away when you’re running and comes back when you’re not
• Pain when pinching between fingers
• Increasing mileage or training intensity causes pain to get worse

Monitor and self-manage if:

• There was some pain following one strange workout
• Symptoms clear up completely in 48-72 hours with rest
• No history of tendon problems and no red flags above

If in any doubt, early assessment will avoid minor overload from developing into chronic tendinopathy.

It is important to be familiar with one of the basic rules before starting to do research. The Achilles tendon is not a standalone tendon. It is located in the middle of a mechanical chain that connects the toes to the foot, ankle, knee, hip and pelvis. This chain is used for both the up and down forces, moving up from the foot and down from the hip, on each and every stride.

This is known as the Two-Way Chain. If one of the links in this chain is weak, stiff or poorly timed, the load is not just lost. It is redirected. One of the most frequent locations for that redirected load to build up until the tissue’s capacity is exceeded is the Achilles tendon.

If you are injured, your first thought is to think about the part of your body that hurts. A runner with Achilles pain ices his heel, stretches his calf and hopes for the best. However, physicians and scientists are gaining more knowledge that injuries do not occur in isolation.

Achilles tendinopathy is an inflammation and pain in the tendon that joins the calf muscle and the heel. It is a common overuse injury in running, affecting approximately 11% of runners at any one time and is one of the most chronic overuse injuries in sport. A lot of runners may have been stymied for months before they find a solution that works.

Modern sports medicine recognizes the body as a kinetic chain. Cumulative overload has often occurred when it has passed a tissue’s biological capacity and the tissue is painful, but not necessarily the cause of the dysfunction.

The Achilles tendon is the biggest and strongest tendon in the human body. It acts like a biological spring, storing and releasing elastic energy during running, and absorbing forces 6–8 times greater than body weight per stride.

When tendons are loaded, they remodel their collagen structure in order to become healthier. As training slowly progresses, the tendon gets stronger. As loading exceeds the tendon’s ability to adapt, the process breaks down and results in disorganized collagen, abnormal tissue changes and chronic pain.

Common contributors include:

• Training errors: volume increases, which are often suggested to be no more than about 10 percent per week.
• Limited ankle dorsiflexion: decreased ankle mobility forces the tendon to take the brunt of the load.
• Muscle weakness: weak calf, hip or gluteal strength changes load distribution.
• Redistribution of force: changes in foot strike, pelvic drop or trunk lean alter biomechanics.
• Poor sleep or nutrition decreases the remodeling ability of the tendon, resulting in recovery deficits.

Treating the tendon alone will not cure the underlying problem.

Perhaps Achilles tendinopathy can have repercussions that ascend up the kinetic chain, all the way to the buttocks.

Take a look at the findings of a study published in October 2013 by Medicine & Science in Sports & Exercise, published by the American College of Sports Medicine. This study included 33 male runners, 19 healthy and 14 with Achilles tendinopathy.

The researchers observed the following:

• Those with the tendon condition had a different manner of moving their feet and striking their heels
• That difference led to the gluteus medius and gluteus maximus muscles firing later than they would have otherwise
• In the presence of tendinopathy, the glutes were not as active as they should have been during running

This is a small sample size, an important limitation as there were only 14 participants in the tendinopathy group. The results presented should be regarded as hypothesis-generating, not as conclusions. They see a pattern that has some significance, but not a universal pattern.

The study found that there was a correlation between Achilles tendinopathy and delayed activation of the gluteals. It did not prove that one caused the other. What it shows is that runners with Achilles tendinopathy have some differences in their running gait, and that these differences are associated with measurable differences in gluteal muscle recruitment.

The clinical effect of the delay, whether it be due to the nature of the drug or the patient’s condition, is the same. When the gluteus medius fires late it is not going to be effective at controlling pelvic drop. A late firing gluteus maximus will not function optimally during hip extension and propulsion. Both gaps impose a larger force on the calf and Achilles tendon to deal with forces that should have been dealt with higher up the chain.

Gluteus Maximus

The gluteus maximus is the largest muscle in the human body. It is responsible for hip extension during running, for generating push-off force, for deceleration of the limb at initial contact and for stabilizing the pelvis. It attaches to the thoracolumbar fascia, which is a vital force transmission pathway between the pelvis and the posterior oblique sling, and is involved in the transmission of forces with each running stride.

With impaired function of gluteus maximus, propulsive demand moves distally to the calf and Achilles tendon. This redistribution over thousands of strides is a significant increase in cumulative tendon stress.

Gluteus Medius

During single-leg stance (about 40% of running cycle), the gluteus medius stabilizes the pelvis. If it fires late or doesn’t shoot enough, the pelvis falls to the unsupported side.

This sets in a mechanical chain; the femur adducts and internally rotates, the tibia follows and the back foot is pushed into over-pronation. This foot position will alter the angle of the Achilles tendon loading, resulting in greater stress over time.

It should be noted that changes in the mechanics of the frontal plane do not necessarily lead to tendinopathy. There are many runners who have some weakness in their gluteus medius but don’t experience any symptoms. The relationship is probabilistic not deterministic.

The foot must be able to absorb impact forces when loading and change to a rigid propulsive lever in a fraction of a second during push-off.

This is achieved by the windlass mechanism. When the heel rises and the toes dorsiflex, the plantar fascia tightens, raising the medial arch and making the foot stiffer for push-off. This mechanism is disrupted if there is a limitation in hallux dorsiflexion, such as hallux rigidus or hallux limitus. The Achilles tendon will then have to produce more plantarflexion force to compensate.

The plantar fascia and Achilles tendon both attach to the calcaneus. Cadaveric studies have shown that these structures are continuous with each other via fascia. One affects the other and coexisting plantar fascia pathology is clinically important in runners with Achilles tendinopathy.

The Two-Way Chain at the foot is used as follows:

• Foot → Hip: prolonged pronation delays the windlass mechanism, driving tibial and femoral internal rotation, increasing demand on the gluteus medius
• Hip → Foot: If the gluteus medius is unable to control the pelvic drop, the rotation of the tibia causes the Achilles to load the rearfoot too much from above.

Both directions need to be evaluated and resolved.

The foot must be able to absorb impact forces when loading and change to a rigid propulsive lever in a fraction of a second during push-off.

This is achieved by the windlass mechanism. When the heel rises and the toes dorsiflex, the plantar fascia tightens, raising the medial arch and making the foot stiffer for push-off. This mechanism is disrupted if there is a limitation in hallux dorsiflexion, such as hallux rigidus or hallux limitus. The Achilles tendon will then have to produce more plantarflexion force to compensate.

The plantar fascia and Achilles tendon both attach to the calcaneus. Cadaveric studies have shown that these structures are continuous with each other via fascia. One affects the other and coexisting plantar fascia pathology is clinically important in runners with Achilles tendinopathy.

Rehabilitation Principles

Successful rehabilitation restores tendon capacity and corrects the mechanical environment that put it under stress. Both are not enough.

Progressive tendon loading is the cornerstone. Current evidence supports:

• Eccentric calf loading (Alfredson Protocol): 3 sets of 15 repetitions of heel drops over the edge of a step, knee straight and knee bent, twice a day, for 12 weeks. This is a considerable time and effort commitment. There will be some discomfort during the exercise; any sharp or increasing pain is an indicator to lower the load.
• Heavy slow resistance (HSR): bilateral and single-leg calf raises, full range of motion with heavy load, 3-4 sets of 6-8 reps, 3x/week. There is some evidence that this can be equally effective and better tolerated by some patients.
• Isometric loading: maintaining calf contractions for 30-45 seconds, helpful in acute phase for pain management.

• Single Leg Bridges: reactivate Gluteus Maximus in low load position
• Clamshells: early on in rehabilitation, focus on gluteus medius and external rotators
• Monster walks: challenge gluteus medius during upright, functional movement
• Step-downs: perform eccentric gluteus medius exercises with a single-leg running stance
• Single-leg balance: develops neuromuscular coordination through hip, knee and ankle

Gait retraining corrects the mechanical contributors that were identified in assessment. Modifying running cadence to increase it by 5–10% decreases peak Achilles tendon loading per stride and is a simple, inexpensive modification for many runners.

Stretching calves will NOT restore tissue quality to the tendon, correct any biomechanical drivers, or restore load-bearing capacity. In insertional tendinopathy, excessive stretching may create symptoms by exacerbating compressive forces at the calcaneal insertion. Stretching is used to support other treatments, but is not a main treatment.

A lack of pain inhibition during effective muscle recruitment, a mechanical barrier because of structural pathology (partial gluteus medius tear, labral lesion, hallux rigidus), or training load that is too high for the tendon to net biological recovery are all potential reasons for failure of strengthening programs. If progress is not being made, then re-evaluate to determine if these barriers are present.

• Running gait analysis: foot strike, pelvic drop, trunk lean, cadence
• Hip strength testing: gluteus medius and maximus
• Timing and sequencing of gluteal muscle activation
• Single leg loading stability of the pelvis
• The first MTP mobility and windlass mechanism quality is well preserved
• Ankle dorsiflexion range
• Strength and endurance in calves, single leg

Two people with the same symptoms can have very different underlying causes and very different treatment options.

If further diagnosis is required, diagnostic ultrasound is our preferred imaging modality of the first choice as it allows the identification of tendon thickening, structural disorganisation, neovascularisation and partial tears in real time. MRI is only used for complex presentations or surgical planning.

Tendon remodeling is a slow process. The collagen turnover in tendon is measured in months, which is much slower than the response of muscle to training within weeks. Early care for runners leads to faster and fuller recovery. The most frequent cause of setback is returning to full training too early.

Practical prevention strategies:

• Gradual mileage progression – a 10 percent per week guideline is a good starting point
• Recoverable days – when tendon remodeling takes place
• Stable posterior chain strength training – calf, glutes and hip stabilisers
• Cadence optimization – 5-10 percent decrease in per stride tendon load
• Tendon adapts to footwear changes, which are gradual
• Monitoring training loads – detect fatigue accumulation before symptoms occur

In either case, the doctor and physical therapist should always take the function of the gluteal muscles into account when evaluating and treating Achilles tendon issues. The 2013 study is part of a series of studies that has been ongoing for some time that running injuries are not usually singular occurrences.

The evidence is sufficient to act upon: The Achilles tendon is part of a system that starts from the trunk and goes to the toes. The first step in successful treatment is to understand each runner’s dysfunctional pattern, rather than treating the painful tendon itself.

Our sports medicine and physical therapy team at NYDN Rehabilitation treats Achilles tendinopathy at its root by employing a thorough movement assessment program, advanced diagnostic ultrasound and personalized rehabilitative strategies. If you are a runner who has heel or tendon pain that persists, give us a call for an appointment.