What condition results in radial wrist deviation upon extension?

Radial wrist deviation during extension occurs when there is an imbalance in the forces acting on the wrist, particularly involving the muscles that control wrist movements. In the case of posterior interosseous neuropathy, which affects the radial nerve, there is weakness or paralysis of the extensor muscles, particularly the wrist extensors and finger extensors, leading to an altered movement pattern.

When the extensor muscles are compromised, wrist extension can result in a deviation towards the radial side. This is due to the fact that other muscle groups, such as the flexor carpi radialis, may become more dominant in this movement. The imbalance created by the weakened extensors and the relatively preserved function of the flexors results in radial deviation during wrist extension.

In contrast, conditions like wrist tendinitis, carpal tunnel syndrome, and fractured wrist typically do not primarily feature radial deviation upon extension. Tendinitis usually presents with pain rather than a specific movement deviation. Carpal tunnel syndrome involves compression of the median nerve and primarily affects finger flexion, not directly impacting the radial ulnar balance of the wrist during extension. A fractured wrist would lead to pain and restricted movement, but not a specific pattern of deviation like that seen with posterior interosseous neuropathy.