The effect of tenotomy and of immobilisation in lengthened and shortened positions on the intramuscular connective tissue of the calf muscles of the rat was studied morphometrically and with a scanning electron microscope. Both tenotomy and immobilisation produced a marked increase in both the endomysial and the perimysial collagen networks, with a simultaneous decrease in intramuscular capillary density. The increase in connective tissue volume was more pronounced and occurred more rapidly in the soleus, which consists mainly of type I, slow-twitch fibres than in the gastrocnemius, which is mainly of type II, fast-twitch fibres. The relative volume of connective tissue increased in parallel with the duration of immobilisation or after tenotomy. There was slightly more increase after immobilisation in a shortened rather than in a lengthened position.

The conservative management of chronic calcaneal paratenonitis is time-consuming and often unsatisfactory. A new, safe and simple technique is described. The crural fascia on both sides of the tendon is incised and left open, adhesions around the tendon are trimmed away, the strongly hypertrophied portions of the paratenon are removed and mobilisation is begun immediately after operation. Between 1961 and 1978 201 such operations were performed on 182 patients 62 of whom were top-ranking Finnish athletes. Only five patients were not athletes. The results, including early return to full activity, were excellent in 169, good in 25 and poor in seven cases. After operation one of the patients gained an Olympic gold medal; others have attained international prominence.