Fig. 189. Synovial Sheaths of the Tendons behind the Internal 



Malleolus. 



The Tendu AchUlis, Plantar Fascia, a large part of the Abductor Muscle of 

 the Big Toe, the Short Flexor of the Toes and the Deep Fascia of the Leg have 

 been removed. The Annular Ligament has been dissected out and the Tendon- 

 sheaths distended with Gelatin. 



Strong Septa extend from the Internal Annular Ligament to the posterior 

 surface of the Tibia, so that the Tendons run in Osteo-aponeurotic Canals, enclosed 

 by synovial sheaths. The Sheath of the Posterior Tibial Tendon commences two 

 inches above the tip of the Internal Malleolus and reaches as far as the insertion 

 of this Tendon into the Scaphoid Bone, so as to extend a little further downwards 

 on the bony aspect of the tendon. Immediately behind this sheath and rarely 

 communicating with its upper end lies the Sheath of the Long Flexor Muscle of 

 the Foot. This sheath extends to a higher level up the leg than the former 

 and is inserted obliquely on the tendon, leaving its posterior border free as long 

 as muscle fibres are inserted into it. 



The sheath ends at the level of the Astragalo-Scaphoid Joint. Still 

 nearer the Os Calais is the Sheath of the Long Flexor of the Big-Toe separated 

 from the Long Flexor of the Toes by a space occupied by the Posterior Tibial 

 Nerve and Vessels on their way to the sole of the foot. This sheath commences 

 one inch above the Tip of the Malleolus and may reach as far as the base of the 

 First Metatarsal Bone. At the point where the Tendon of the Long Flexor of 

 the Big-Toe crosses the Long Flexor of the Toes and has a band of communication 

 with the latter, the Tendons still remain within their proper sheaths, but these 

 sheaths communicate with each other ; in many cases the Long Flexor of the Big- 

 Toe is without synovial covering at the point of crossing. 



Like the tendon-sheaths in the hand, these sheaths are of importance in 

 connection with the spreading of inflammatory processes from the foot to the leg 

 and vice versa. Moreover, as they pass over the Capsule of the Ankle-joint 

 disease may perforate these Sheaths and extend to the Ankle-joint or in the 

 reverse direction. 



At the toes the Flexor Tendons, like those of the Hand, have sheaths 

 with one important difference; at the toes they never communicate with the 

 Central Synovial Sheaths. 



