Answer
Only two real joints are formed between the radius and the ulna. However these two bones are connected in three places
1. The proximal radioulnar joint. This is the jont between the head of the radius and the radial notch of the ulna.
2, The distal radioulnar joint. This is the joint between the ulnar notch of the radius and the head of the ulnar
These two joints are pivot joints. There is however a third membranous connection between the radius and the ulnar . This is an interosseous membrane that constitutes a kind of joint called a syndesmosis
Work Step by Step
The two joints between the ulnar and the radius are the proximal radioulnar joint-- between the head of the radius and the radial notch of the ulna and the distal radioulnar joint-- between the ulnar notch of the radius and the head of the ulnar.
Between these two joints, the radius and the ulnar are also connected by a broad connective tissue ligament, the interosseous membrane . This membrane holds the radius and the ulna together during pronation and supination, and transfers forces from one bone to the other. It is also a point of attachment for some forearm muscles.
