To detect the presence of instability at the inferior radio-ulnar joint (IRUJ).

Isolated involvement of the IRUJ is rare and is usually associated with more significant injury at the wrist (i.e. fracture or dislocation). Minor disruption may cause pain as the primary sign and this would be well localized with tenderness easily elicited by palpation (see clinical tip). Pain at the end of passive pronation and supination would also be provocative. Where ligament disruption has occurred, excess movement will be accompanied by apprehension during certain activities, particularly in weight-bearing positions where its lack of stability is more seriously tested.

Fig. 4.1 Piano key test.

The IRUJ is often involved in inflammatory arthritis and in more severe cases, the synovitis afflicting the joint causes a destructive process resulting in pronounced loss of rotation, dorsal prominence and instability of the ulna, as well as localized swelling and loss of the normal function of the adjacent extensor carpi ulnaris, a condition known as caput ulnae syndrome (Brown & Neumann 2004). Given the associated joint stiffness, despite the instability at the IRUJ, the piano key test may not yield a positive result.

The joint line is easily palpable on the dorsum of the lower forearm. The width of the wrist dorsally can be divided into three equal portions, making the joint line the marker between the most medial and middle sections.

If the result of this test is ambiguous further accessory testing of the IRUJ can be done to detect changes in range and end-feel.

EXPERT OPINION	COMMENTS
	Piano key test
	Especially useful to determine level of instability – only a very unstable joint will behave like a true ‘piano key’.

Wrist adduction test

To stress the radial collateral ligament (RCL) and lateral capsule of the wrist in order to detect pain and/or laxity.

This test is most likely to identify an isolated sprain of the RCL where localized pain around the anatomical snuffbox would be the primary complaint. Depending on the severity of the trauma, a varying but equal degree of flexion/extension restriction may also be present at the wrist as the ligament blends with, and reinforces, the lateral joint capsule, thereby causing capsular limitation. As the history is usually traumatic, careful screening is necessary (including X-ray evaluation in most cases) to eliminate fracture of the carpus – the scaphoid being the usual culprit. With pain reported in this area, osteoarthritis of the trapeziofirstmetacarpal joint (basal joint of the thumb; see axial compression test, p. 129) and de Quervain’s tenosynovitis (see Finkelstein’s test, p. 131) are other possible diagnoses to consider.

The RCL can be found by identifying the radial styloid at the base of the anatomical snuffbox and moving the finger slightly distally with the wrist in a degree of radial deviation. The ligament and capsule are relaxed in this position. Keeping the finger in place, the RCL tautens (if intact) and becomes easily palpable as the wrist is passively taken into ulnar deviation.

Make sure the patient’s thumb is not involved in this movement in order to avoid stress being placed on the thumb abductor and extensor tendons which may result in a false positive finding being recorded.

EXPERT OPINION	COMMENTS
	Radial collateral ligament stress test
	Usually included as part of radiocarpal assessment without specifically testing the ligaments as they are rarely injured in isolation.

Wrist abduction test

To stress the ulnar collateral ligament (UCL) and medial capsule of the wrist in order to detect pain and/or laxity.

The patient reports localized pain located at the inner, medial aspect of the wrist joint. If the UCL stress test is the only positive test, confirmation of the lesion can be made by palpation – tenderness is usually identifiable at its origin on the ulnar styloid. Isolated injury to the UCL is rare and, because of its anatomical connection, is more commonly associated with injury to the triangular cartilaginous complex (see TFCC test, p. 127). Medial wrist pain may also emanate from the inferior radio-ulnar joint (see piano key test. p. 114) and the extensor carpi ulnaris tendon.

The ligament is most easily identified by finding the styloid with the wrist in ulnar deviation and then passively moving the wrist radially until the ligament can be felt tautening under the finger.

EXPERT OPINION	COMMENTS
	Ulnar collateral ligament stress test
	Usually included as part of radiocarpal assessment without specifically testing the ligaments as they are rarely injured in isolation.

Watson test

To establish the presence of abnormal movement of the scaphoid and lunate bones indicating instability or subluxation.

Although comparatively rare, the instability that results from disruption of the scapholunate articulation is the most common carpal instability. A complete tear of the scapholunate ligaments, usually resulting from a severe hyperextension injury, will lead to significant scapholunate dissociation and disruption to the normal motion of the proximal carpal bones during wrist movement. Because of the loss of connection between the scaphoid and lunate, the scaphoid rotates into a degree of flexion leaving the lunate and triquetral free to rotate into extension which causes pain, an inability to weight-bear on the wrist and an overall loss of function (Placzek & Boyce 2006). Chronic instability of the joint also strongly predisposes to a recognized sequence of osteoarthritis involving the unstable capitolunate and capitoscaphoid articulations (particularly in the presence of a dorsally subluxed capitate) and, more latterly, the radioscaphoid and radiolunate joints, a sequence known as scapholunate advance collapse (SLAC) (Miller & Schweitzer 2005).

The normal extent of separation between the scaphoid and lunate bones should be less than 2 mm (Gross et al 2002) but a diastasis of more than 3 mm is pathognomonic of scapholunate dissociation and should be detectable on plain X-rays (McRae 1990). The evident space between the bones is known as the Terry Thomas sign, named after the 1960s comedian who famously had a gap between his two front teeth (Placzek & Boyce 2006).

Using a cadaver model where the wrist was progressively loaded in extension and ulnar deviation (the most common mechanism of injury), a sequential, four-staged pattern of injury was noted; scapholunate diastasis, dorsal subluxation of the capitate, disruption of the lunotriquetral ligament and complete dislocation of the scapholunate articulation (Brown & Neumann 2004). Subluxation of the capitate (see clinical tip) is therefore usually associated with injury to the proximal carpus although it does not have to involve catastrophic disruption of the scapholunate articulation (see capitate apprehension test, p. 124).

It is not always necessary to reproduce subluxation with this test as it is usually painful for the patient and they are likely to indicate apprehension as the forces are gradually applied. The presence of pain and apprehension are good indicators of instability and, as an alternative, detecting increased excursion without causing subluxation can be achieved by applying an anterior/posterior glide to the scaphoid in a neutral position and comparing with the opposite side.

The possibility of capitate subluxation should be considered by observing the dorsum of the wrist in a flexed position where a bony prominence may be noted. Passive wrist extension will also be painfully blocked, particularly on weight-bearing.

Care should be taken when interpreting the findings as up to 30% of healthy wrists can give a false positive result due to general ligamentous laxity at the wrist. It is thought that repeating this dynamically (see variations), particularly when the patient makes a fist, reduces this tendency (Weiss & Finkelstein 2005).

EXPERT OPINION	COMMENTS
	Scaphoid shift test
	A tricky test to perform, as well as interpret, but very useful once perfected.

The scaphoid stress test is a simple modification where the patient actively moves the wrist from ulnar to radial deviation while the scaphoid is stabilized by the examiner in the same way. Apprehension and/or a painful clunk during the movement demonstrates dynamic subluxation.

To establish the presence of abnormal movement of the lunate and triquetral bones indicating instability or subluxation.

Differing descriptions for this test can be found in the literature and this has led to the same test being assigned several names. Injury to the lunotriquetral articulation is uncommonly encountered (see scaphoid shift test, p. 119) requiring impact in extension and radial deviation (Brown & Neumann 2004). A strain to the lunotriquetral ligament may be evident with localized tenderness and a positive test, but if the trauma has been sufficiently significant to cause disruption of the articulation, normal kinematics will be lost. The combined unit of the scaphoid and lunate rotate into flexion leaving the untethered triquetral to drift into extension. Pain, apprehension, a reluctance to move and weakness will all be reported by the patient, with a more significant injury likely to predispose to osteoarthritis (Placzek & Boyce 2006). Lunotriquetral ligament injury is often associated with triangular fibrocartilage complex (TFCC) tears (see TFCC test, p. 127) and MRI can therefore be helpful in making the distinction (Miller & Schweitzer 2005). There are no studies examining the reliability of this test and considerable skill is required to interpret the findings meaningfully.

An isolated injury to the lunotriquetral ligament does not usually produce a static diastasis between the lunate and triquetral so there may be dynamic and functional instability present but a normal plain X-ray reported.

EXPERT OPINION	COMMENTS
	Lunotriquetral shear test
	It is important to establish what is normal excursion on the unaffected side as differences in range can be subtle.

Murphy’s sign may also indicate the presence of lunate dislocation. The patient is asked to make a fist and the relationship between the heads of the 2nd, 3rd and 4th metacarpals is examined. Normally the head of the 3rd metacarpal extends more distally but where the lunate has dislocated, it remains in line with the heads of the other two metacarpals.

Capitate displacement test

To determine the presence of capitate instability.