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Is Plantaris A Cause Of Achilles Tendinosis?

Is Plantaris A Cause Of Achilles Tendinosis?
Is Plantaris A Cause Of Achilles Tendinosis?

Plantaris Muscle: More Than Just A Hypothetical Cause Of “Tennis Leg”

The relatively common condition “tennis leg” occurs most frequently during running or jumping and usually results from an eccentric load placed across the ankle with the knee in an extended position, whereby often the athlete feels as though they were struck on the calf by an object such as a ball or other piece of equipment like a racquet. There is dispute in the medical community over the role if any that the plantaris muscles plays in “tennis leg,” tears or rupture of the muscle are described as one of the various possible etiologies of “tennis leg” however their involvement in “tennis leg” or Achilles tendinosis is a source of controversy in the literature.

More recently there has been interest in the role of the plantaris tendon in Achilles tendon pain. In Achilles tendinopathy pain is often most prominent on the medial side, 2-7cm from the insertion of the tendon onto the calcaneus in what is often referred to as the midportion of the tendon. The medial location of the pain has previously been explained to be caused by enhanced stress on the calcaneal tendon due to overpronation.
However on this medial side of the Achilles tendon is where the plantaris tendon is located and it has been postulated that the plantaris tendon might play a role in these medially located symptoms.

Basic Relevant Anatomy Of The Plantaris Tendon

The tendon travels inferiorly along the medial aspect of the Achilles tendon, which it accompanies to its insertion on the calcaneus and in some situations the tendon may insert independently of the Achilles tendon. Differential movement of the tendons is hypothesized to possibly create abrasion and adhesions in the tendon which tend to be found in the painful mid-portion zone of the Achilles tendon in Achilles tendinopathy.
Clinical and histological studies are needed to confirm the role of the plantaris tendon in mid-portion Achilles tendinopathy, however some anatomical studies when comparing the material properties of the Achilles and plantaris tendons and found plantaris to be stiffer and stronger, suggesting that it could tether the Achilles.

The Plantaris Hypothesis For Cause Of Mid Tendon Medial Achilles Tendinosis

Some research has suggested a thickened plantaris tendon located in close relation to the medial Achilles is common in patients with chronic painful midportion tendinosis. A thickened tendon is suggested to increase compression and induce reactions within the cell and matrix and it is hypothesised that adhesions between the Achilles and plantaris tendons may cause pain by intertendinous traction on sensory nerve fibres.

More Research Required

The role of the plantaris tendon in midportion Achilles tendinosis needs to be further evaluated, however should be included in any differential considerations of potential causes of Achilles tendinopathy.
Literature on proper management for muscular injury of plantaris is scarce, as well as any literature to the role that the muscle may play in functional mechanics. Further research is needed in order to assess the muscle’s importance to mechanics of the calf muscle as well as its any potential role in any other conditions including non-insertional Achilles tendinopathy. Considering that it is suggested non-insertional tendinopathy makes up 66% of Achilles tendon pain, unlocking any possible involvement of the plantaris tendon in Achilles tendon pain and consequently how best to manage this could be of great benefit to many athletes out there.

Disclaimer: Sydney Physio Clinic does not endorse any treatments, procedures, products mentioned. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific advice or assistance regarding Achilles Tendinosis should consult his or her orthopaedic surgeon, sports medical specialist, general practitioner or physiotherapist.

Hayden Latimer is the founder of and principle physiotherapist at Sydney Physio Clinic. Since graduating from Otago University, Dunedin, New Zealand he’s gained wide experience practicing across the globe for over 15 years and is now extremely knowledgeable in helping people reduce discomfort and restore function and mobility.