What can be the cause of tendor sore heels?

Plantar fasciitis: Plantar fasciitis is the most common cause of heel pain. This involves inflammation and/or microtearing of the thick fibrous/ligamentous tissue called the plantar fascia. Many factors are linked to pf: age, weight gain, overtraining, poor footwear, flat foot, high arch, tight/weak calf muscles, etc. The internet can provide some calf stretching exercises. Many treatment options exist.

Achilles Tendonitis: If the soreness is at the back of the heel then it may be tendonitis of the Achilles tendon. This usually responds to nsaids, rest, and gentle but regular stretching exercises.

Agree plantar fascia: Inflammation of the plantar ( bottom part) fascia(connective tissue - forming the tendons that surround the heel / arch of the foot) - causes heel pain - possible due to weight gain, walking too much in too high heels or bare-footed. Occasionally associated with heel spurs - if goes on for way too long - need to be seen to evaluate and diagnose and advise treatment - usually over the counter....

Plantar fasciitis: Plantar fasciitis is an inflammation or deterioration of the tissue that makes up your foot arch. Best managed with stretching your arch and soft supportive orthotics/shoe inserts. Night splints can sometimes be of benefit. Cortisone injections are also popular and effective. There has been recent interest in platelet rich plasma injections. Avoid surgery if possible.

Could be...: Plantar fascitis if the pains occur mainly in the heel area and even possibly the arch. It could also be generalized arthritis and a number of other possibilities. Take the insoles out of your shoes and replace them with ones that have more arch support. The one i recommend most is the spenco polysorb cross-trainer insole. If you don't need as much cushioning, the total support is also good.