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Thumb Radial Collateral Ligament Injuries

Original Editor - Habibu Salisu Badamasi
Top Contributors - Maryellen Tighe, PT, DPT, Habibu Salisu Badamasi, Caroline Stone, Vidya Acharya, Alexandra Stead and Kim Jackson

Introduction

Two major ligaments stabilise the metacarpophalangeal (MCP) joint of the thumb: the ulnar collateral ligament (UCL) and the radial collateral ligament (RCL)[1]. The RCL is the primary lateral stabiliser of the radial side of MCP joint[2]. Damage to this ligament results in varying degrees of instability and functional impairments[2] [3]. The RCL is injured in about 32% of injuries to the collateral ligaments[3]. Approximately 50% of the time, injury is caused by an axial load[4]. RCL injuries are more likely to be the result of sports injuries[3]. Comparatively, UCL injuries such as Skier’s Thumb and Gamekeeper’s Thumb, are often caused by an abduction movement[4].

RCL injuries are slower to be reported to healthcare providers than UCL injuries[3]. UCL injuries are generally reported in less than 10 weeks, whereas RCL injuries are reported in greater than 10 weeks[4]. RCL injuries are also more likely to need surgery[4]. Chronic weakness or overstretching can lead to MCP instability, a loss of pinch grip strength and degenerative changes to the MCP joint[5].

Clinically Relevant Anatomy

The thumb MCP joint is a condyloid joint, allowing it to move in two planes: the sagittal and coronal. Flexion and extension occur in the sagittal plane, and adduction and abduction occur in the coronal plane. However, the MCP of the thumb acts as a hinge joint, which prioritizes stability over mobility[3]. The joint is supported and moved by:

  • Volar plate - a short transverse thickening of the joint capsule that prevents hyperextension and increases congruence[1]
  • Joint capsule fibres[1]
  • passive stabilisers including the RCL and UCL[3]
  • dynamic stabilisers including the flexor pollicis brevis, abductor pollicis brevis and adductor pollicis[3].
  • Deep transverse metacarpal ligament -  connects the second to fifth metacarpal heads. Its attachment on the thumb includes bands that centre the MCP joint and stabilise its extensor tendons.[1]

The thumb is not symmetrical on its radial and ulnar side. Some clinically important asymmetries include:

  • The adductor pollicis, when not restricted by the RCL, tends to cause increased joint instability, with ulnar and volar joint subluxation[5].
  • There is no adductor aponeurosis on the radial side of the thumb. A common complication of a ruptured UCL (occurring in 60%-90% of tears) is that it can get caught in this  tendinous complex, requiring surgery for the tendon to return to its origin[3][6][7]. While there is limited evidence of a similar pattern happening with the RCL[8], there is still a risk of instability due to the adductor pollicis as noted above.

Mechanism of Injury / Pathological Process

RCL tears are caused by axial loading or by thumb metacarpophalangeal adduction moment[4][5]. Axial loading results in increased stress through the thumb. The increased volume of tendons and ligaments on the ulnar side prevents ulnar sided injury with axial loading[2]. The radial side is unable to support the pressure, and is ultimately injured. Adduction forces may also result in injury, as the RCL limits adduction[2]. This differs from the UCL which is more often injured by abduction forces. In some types of injuries, both ligaments may be ruptured[5]. RCL tears are also more often accompanied by MCP joint subluxation than UCL tears. 36% of RCL injuries are accompanied by an MCP joint subluxation, compared to 17% of UCL injuries[9].

Clinical Presentation

Patients with RCL injury will often present with:

  • Thumb MCP joint pain[5]
  • Thumb MCP weakness, specifically with key pinch grip[5]
  • Swelling and ecchymosis in the acute setting, as well as point tenderness over the proximal origin of the ligament at the metacarpal head[5]

Assessment

An avulsion fracture at the base of the proximal phalanx of the thumb is present laterally. The fragment is rotated and involves the articular surface. Features are typical of a radial collateral ligament avulsion.[10]

Physical therapy examination should consist of range of motion (ROM), strength, and selective tissue testing to assess for RCL injury. Due to the frequency of subluxations, patients with suspected RCL injury should be referred for X-ray and MRI to determine prognosis and whether candidates should proceed with conservative or more invasive measures[9].

Range of Motion: Thumb ROM may display mixed results. ROM may be limited in an acute injury due to pain and guarding. In the case of a chronic injury, the ROM may be increased, especially into abduction, due to chronic adductor pollicis stretching. Normal thumb ROM values are as follows:

  • MCP flexion: 60 ° (range of 43–70 °) [11]
  • MCP extension  8.1 ° ( range of 0–15 °)[11]
  • CMC joint anteposition: 61.2 ° (range of 50–71 °)[11]
  • CMC joint retroposition: 31.1 ° (range of 25–38 °)[11]
  • CMC joint radial abduction: 62.9 ° (range of 53–71 °) [11]
  • CMC joint radial adduction: 10.2 ° (range of 5–20 °) [11]

Strength: manual muscle testing of the MCP should be performed in full extension assessing the RCL, UCL and volar plate, and in 30 degrees of flexion to isolate the RCL[5].

Ligamentous Assessment: A positive test for an RCL injury would be laxity to radially directed stress of 15 to 30 degrees relative to the unaffected side[3][5]. If a subluxation is present, patients may present with an excessive dorsoradial prominence of the radial condyle of the metacarpal head[3]. Any subluxation identified on examination could contribute to perceptions of laxity[5]. Anterior and posterior stability of the joint should be assessed to test for a dorsal capsular structure or volar plate injury[5].

Differential Diagnosis

RCL injuries do not always occur in isolation. Other parts of the MCP joint may also sustain injury with similar mechanisms. Some additional diagnoses that may occur with or instead of a potential RCL injury include:

At the MCP joint:

If the pain is not localised to the side of the hand and instead is located closer to the wrist, consider:  

If the patient demonstrates several other symptoms affecting the whole hand consider:

Classification of Injury

Injuries to the RCL are classified based on a three grade classification. They are graded in severity from Grade 1 (least severe) to Grade 3 (most severe).

  • Grade 1: Partial ligament tear where the ligament is functionally intact. Patient will present with localised pain, tenderness to palpation, but without evidence of instability[3][5].
  • Grade 2: Partial thickness tear. Patient will demonstrate ligamentous laxity, but with a firm end point[5]. Patients will present with increased pain and swelling compared to grade 1[3]. Laxity remains below the threshold for a complete rupture[3].
  • Grade 3: Complete ligament rupture. The patient will demonstrate increased laxity with no end point with manual stress testing[5].

Outcome Measures

The Disabilities of the Arm, Shoulder and Hand (DASH) (or the shortened QuickDASH) and the Michigan Hand Outcomes Questionnaire are validated upper limb outcome measures that are commonly used post RCL injuries. A clinician may also find the following outcome measures useful to assess functional impairment and monitor recovery following RCL injury of the thumb:

Management / Interventions

Surgical

RCL injuries are more likely to require surgical management than UCL injuries[3]. The ligament often heals in an elongated position due to adductor pollicis tension, resulting in excessive thumb instability[5].  This is especially important if there is also subluxation[9]. The surgery can be delayed for patients with this injury without compromising the chance of primary repair. This is a more common choice for athletes who are able to perform at a high level in a cast or brace[5].

For most chronic tears, a reconstruction of the ligament is not necessary for repair of the RCL and the surgeon is able to use the native RCL tissue[5]. If a reconstruction is done, it is most often done with ipsilateral palmaris longus using local tissue rearrangement, like a portion of the abductor pollicis brevis. Surgical concerns vary based on the chronicity of the injury. The ligament repair should be tensioned in about 30 degrees of MCP joint flexion to avoid over-tightening[5]. The repair should also correct pronation which may occur with a chronic RCL injury. Repairs of other injuries should be completed in the same surgery[5].

The post-operative course of care catches up with the grade 1 to 2 injury course of care above, as patients are immobilised in a thumb spica cast or splint for up to 6 weeks [5].

Conservative

Grade 1 or 2 injuries: These may be successfully treated non-operatively for patients who desire a pain-free return to activities. They may wear a thumb spica cast for 4 to 6 weeks, progressing to a removable cast until symptoms are fully resolved[12][5].

Rehabilitation

All grades of injury should begin with ROM. Patients should move the joints above (elbow, wrist) and below (thumb interphalangeal joint) as much as possible while immobilised or in a splint. It is especially important to move the IP joint as it is most prone to increased tension and this will promote appropriate movement through the surgical site[13]. For surgical patients, ROM will be progressed to strengthening at approximately 3 months post-op[14]. For non-surgical patients, ROM is progressed to strengthening as full ROM is achieved and to the patient’s pain tolerance. Strength should focus on grip and pinch strength[15][14].   Athletes may return to sport when full motion and strength have been achieved and sport-specific activities have been resumed without pain[5].

Conclusion

Radial collateral ligament injuries often occur due to axial loading of the thumb MCP joint. These injuries are more often diagnosed in the subacute or chronic phase[3]. Early diagnosis is crucial, as delayed or missed diagnosis can lead to instability, osteoarthritis and increased functional impairment[3]. Conservative management can be successful for grade I-II injuries, while grade III injuries typically require surgical management.

References

  1. ↑ 1.0 1.1 1.2 1.3 Okafor L, Sinkler MA, Launico MV, et al. Anatomy, Shoulder and Upper Limb, Hand Metacarpal Phalangeal Joint. [Updated 2023 Oct 24]. StatPearls. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538343/ (accessed 12 May 2026).
  2. ↑ 2.0 2.1 2.2 2.3 Bouredoucen H, Taihi L. Thumb metacarpophalangeal joint. Part I: anatomy, biomechanics, and imaging techniques. Rofo. 2026 Apr 14.doi: 10.1055/a-2834-3432
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 Bouredoucen H, Taihi L. Thumb metacarpophalangeal joint - part II: pathologies and imaging findings Rofo. 2026 Apr 16. doi: 10.1055/a-2830-5647.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Taylor KF, Lanzi JT, Cage JM, Drake ML. Radial collateral ligament injuries of the thumb metacarpophalangeal joint: epidemiology in a military population. J Hand Surg Am. 2013;38(3):532–536.
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 5.20 5.21 Mitchell TW, Mitchell SA, Wu C. Radial Collateral Ligament Injuries of the Thumb Metacarpophalangeal Joint. Curr Rev Musculoskelet Med. 2022;15(6):581-589.
  6. ↑ Lucerna A, Rehman U. Stener Lesion. StatPearls. 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541004/ (Accessed 12 May 2026).
  7. ↑ Mahajan M, Rhemrev S. Rupture of the ulnar collateral ligament of the thumb – a review. Int J Emerg Med. 2013 Aug 12;6:31. doi: [1]
  8. ↑ Doty JF, Rudd JN, Jemison M. Radial collateral ligament injury of the thumb with a Stener-like lesion. Orthopedics. 2010;33(12):925.
  9. ↑ 9.0 9.1 9.2 Hoy JF, Ward CM, Kim JH, Simcock XC. Thumb Radial Collateral Ligament Injuries Show Greater Rates of Metacarpophalangeal Subluxation Compared With Thumb Ulnar Collateral Ligament Injuries: A Comparative Imaging Analysis. Hand (N Y). 2026;21(5):737-743.
  10. ↑ Case courtesy of Frank Gaillard, Radiopaedia.org. From the case rID: 198704
  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 Barakat MJ, Field J, Taylor J. The range of movement of the thumb. Hand (N Y). 2013; 8(2):179-82.
  12. ↑ Chhor K, Culp R. Baseball Commentary “Thumb Ligament Injuries: RCL and UCL.” Hand Clinics, 2012; 28:371-372
  13. ↑ Saunders R, Astifidis R, Burke S, Higgins J, McClinton M. Hand and Upper Extremity Rehabilitation: A practical Guide. 4th Edition. St. Louis, MO: Elsiver, 2016. p. 406-407.
  14. ↑ 14.0 14.1 George S, Rizkallah M, et al. Early vs late surgical treatment of radial instability of the thumb metacarpohalangeal joint. A retrospective cohort study. Hand surgery and Rehabilitation. 2021;40:771-776
  15. ↑ Langdell H, Zhang G, Pidgeon T, et al. Management of Complex Hand and Wrist Ligament Injuries. Hand Clinics, 2023; 39:367-377
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