The scapholunate interval is a small space within the wrist between the scaphoid and lunate bones. The space is supported by a strong, special ligament (the scapholunate ligament). This ligament is flexible but can still sustain an injury, particularly due to a direct fall onto the hand while playing sports or engaging in other activities. Overuse can also predispose to scapholunate ligament, for example, in manual workers or those lifting heavy weights in the gym. Scapholunate ligament injury usually causes localised wrist pain that worsens when you grip objects or put extra pressure on your hand, such as during push-ups.
Relevant Scapholunate Ligament Anatomy
The Scapholunate ligament connects two important wrist bones together, the lunate and scaphoid. These are found within the proximal row of the wrist on the thumb side. The ligament has three parts - ventral, dorsal and interosseous. The ligament is crucial in ensuring the normal transfer of forces across the wrist joint. Therefore, scapholunate ligament injury can result in wrist joint instability and osteoarthritis.
What are the causes of scapholunate ligament injury?
Scapholunate ligament tears commonly result from wrist injuries or falls, but overuse without a traumatic incident is also a known cause. This is frequently observed in sports that put excessive strain on the wrist, such as weightlifting and gymnastics.
How to tell I have a scapholunate ligament injury?
If you have a scapholunate ligament injury, you may experience the following symptoms:
- Pain and swelling in your wrist joint after a fall or injury that persists even with rest and worsens with activity.
- Feeling of instability and weakness in your wrist joint
- Wrist pain during activities that put pressure on your wrist, such as when playing tennis or lifting heavy objects.
What other conditions can be confused with scapholunate ligament injury?
Wrist problems that can be mistaken for Scapholunate ligament injury include:
Scapholunate ligament injury vs wrist osteoarthritis (OA)
Both scapholunate ligament injury and osteoarthritis can cause wrist joint pain, exacerbated by putting extra pressure on the wrist joint in both conditions. Scapholunate ligament pain usually occurs after a specific event, like falling on your hand. Wrist osteoarthritis, on the other hand, usually develops gradually in older individuals without any prior trauma. People with wrist joint osteoarthritis usually describe a more generalised pain associated with joint stiffness in the morning. If left untreated, scapholunate ligament injury can lead to wrist instability, increasing the risk of wrist arthritis. Therefore, it is important to get a prompt diagnosis, and imaging tests play a crucial role in this process.
How to diagnose scapholunate ligament injury?
As it's essential to get an accurate diagnosis for scapholunate injuries because delayed or missed, diagnoses can result in long-term wrist pain and even osteoarthritis. The condition is usually suspected after clinical assessment by a hand specialist. Imaging is then indicated to establish the diagnosis and rule out other causes of wrist pain.
A wrist X-ray is t performed to determine if there is a scapholunate ligament tear. The bones’ alignment, specifically the scaphoid and lunate, is examined to ensure they are properly aligned and positioned next to each other in the X-ray. A disrupted alignment or increased gap between the scaphoid and lunate indicates a scapholunate ligament tear. An additional X-ray may be taken while asking the patient to make a fist, which increases stress on the ligament and helps with assessment. An MRI is also useful in assessing the severity of the injury (partial vs complete) and ruling out other causes for wrist pain (like scaphoid or distal radial fractures).
A clenched view wrist X-ray showing fracture of the scaphoid bone, which is an important mimic of scapholunate ligament injury.
What is the treatment for scapholunate ligament injury?
Treatment will depend on the severity of the scapholunate ligament tear and the stage of the injury. If the injury is of high grade, a specialist hand surgeon orthopaedic referral is recommended, as the treatment usually involves surgical ligament repair. Conservative management is usually considered in low-grade (partial) ligament injury. These include resting the area using a splint for approx. 4 weeks followed by physiotherapy and strengthening exercises. If the symptoms persist, an orthopaedic referral is recommended. In some circumstances, an ultrasound-guided steroid injection can be considered part of the treatment plan.
What is a Scapholunate ganglion cyst?
Injury to the scapholunate ligament can result in a ligament sprain, forming a tiny fluid-filled cyst near the ligament. This is referred to as a wrist 'ganglion cyst'. It is often asymptomatic but can cause local pain and discomfort. To learn more, please see our article about ganglion cysts. An ultrasound examination is an excellent tool for assessing a suspected Scapholunate ganglion cyst. Ultrasound-guided aspiration and steroid injection can be considered a treatment option. Ultrasound guidance ensures accuracy, and injecting a small dose of cortisone reduces the possibility of recurrence.
