The infraspinatus muscle inserts at this tendon to the distal greater tubercle of the humerus. This tendon stretches across the shoulder joint to attach to the humerus and in doing so acts as a very strong ligament to hold the joint surface in apposition. This structure restricts the movement of the shoulder joint to flexion and extension (together with the suscapularis tendon and the supraspinatus tendon). A bursa lies under this tendon at the greater tubercle of the humerus. The bursa is lined by a synovial membrance and filled with synovial fluid and protects the infraspinatus tendon and the shoulder joint by allowing the transmissions of tension and sheer forces around an angle. [ MURDOCH:963 ]