Introduction

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that mainly impacts synovial joints. The condition can cause inflammation, joint damage, deformity, and disability, as well as extraarticular symptoms such as tenosynovitis. The most common initial appearance of rheumatoid arthritis is inflammatory arthritis affecting the small joints of the hands. The metacarpophalangeal, proximal interphalangeal, and wrist joints are the most typically affected hand joints. The frequent episodes of inflammation can have negative effects on wrist function in the long term. Yet, few studies have examined the consequences of rheumatoid arthritis at the level of the wrist. Therefore, this study wanted to shed light on sensorimotor wrist function in rheumatoid arthritis and how these correlate to pain and disability.

Methods

The current study employed a cross-sectional design involving patients with rheumatoid arthritis and healthy controls. Eligible participants were screened based on the 2010 ACR/EULAR rheumatoid arthritis classification criteria. They were not eligible in case they had increased disease activity, measured through a CRP exceeding 5mg/l and a DAS28-ESR score exceeding 3.2.

The following measures were obtained:

1. Isokinetic Muscle Strength: Flexor and extensor muscle strength of both wrists was evaluated using an isokinetic dynamometer at a velocity of 30°/sec across a range of 80° (40° flexion and 40° extension). Five repetitions were performed at maximum effort after three warm-up trials, with a 2-minute rest between measurements.Participants were seated with the forearm and elbow stabilized to isolate wrist motion.Muscle strength was analyzed using peak torque normalized to body weight.
2. Joint Position Sense (Proprioception): Proprioception was measured using the dynamometer in the form of joint position error (JPE). The participants were taught a target angle (30° wrist extension). After practicing, they were asked to recreate the target angle three times, and the absolute angular error (difference between perceived and actual angle) was recorded.
3. Hand Grip Strength: Hand grip strength was measured using a hand dynamometer, with participants seated and forearms in a neutral position. Three trials were performed with maximal effort.
4. Wrist-Related Pain and Disability: The Patient-Rated Wrist Evaluation (PRWE) questionnaire, assessing pain (5 items) and function (10 items), was used to evaluate wrist disability. Scores ranged from 0 (no disability) to 100 (maximum disability). Each subscale accounts for a maximal score of 50.

Results

Thirty-one people with rheumatoid arthritis and an equal number of healthy controls were included. The average age of the healthy controls was 47 years and the participants with rheumatoid arthritis were on average 54 years old. The included rheumatoid arthritis patients had a mean disease duration of 14.6 years (+/- 8.6 years). No differences were observed between both groups at baseline.

The assessment of wrist function in rheumatoid arthritis patients revealed lower muscle strength of the flexor and extensor muscles compared to the healthy controls, both for the dominant and non-dominant wrists. This deficit was more pronounced in the flexor muscles.

• Dominant wrist flexor strength in rheumatoid arthritis patients averaged 10 ± 4.6 Nm/kg versus 14.4 ± 4.8 Nm/kg in controls.
• Extensor strength also showed significant deficits (7.6 ± 4.7 Nm/kg vs. 10.2 ± 3.4 Nm/kg in controls).

Considering proprioception, impairments were found in rheumatoid arthritis patients, as reflected in higher JPE values. They had greater difficulty accurately perceiving joint angles, with mean errors of 6.5° for the dominant wrist and 7.7° for the non-dominant wrist, compared to 4.1° and 3.6° in healthy controls.

• A negative and weak correlation was found between flexor and extensor muscle strength and joint positioning error of the wrist. (r= -0.2 for both)
• A strong positive correlation was found between grip strength and wrist flexor and wrist extensor strength (r = 0.7 and r = 0.6, respectively)
• There was a weak negative correlation between wrist joint position error and hand grip strength (r = -0.3)
• No significant correlation was found between muscle strength, proprioception, and the PRWE pain or disability scores.

Questions and thoughts

Outcomes from the PRWE reveal that people with rheumatoid arthritis show significant levels of pain in their daily activities, in both the dominant and nondominant wrist. Function levels are somewhat less affected. Given that these people were not in a flare at the time of the study, this is especially important to remember from this study.

Compared to the healthy controls, worse strength was found for both the dominant and non-dominant wrists and wrist flexion and extension. The same was true for joint position error; rheumatoid arthritis patients had increased positioning error compared to the healthy controls. Remembering that these people did not report wrist pain, the importance of assessing sensorimotor wrist function in rheumatoid arthritis patients seems of uttermost importance. Especially given the fact that the disease is known to affect the synovial joint and related structures and the wrist is negatively affected in many people with rheumatoid arthritis.

A strong positive correlation was found between grip strength and wrist flexor and wrist extensor strength (r = 0.7 and r = 0.6, respectively), meaning that the higher the grip strength was, the higher the strength of the wrist flexor and extensor muscles. This would imply that you could train the wrist flexors or give exercises that implement grip to improve wrist flexor strength, or vice versa.

By determining the correlation between all measured variables, we can see how they relate. However, this study did not determine the causes, since correlation does not imply causation. Yet, a correlation shows that two variables follow a predictable pattern. This may identify potential relationships.

Talk nerdy to me

Grip strength was assessed as a variable, but besides how it correlated to the other variables no raw data were given to compare between the dominant and non-dominant hand or between healthy controls and rheumatoid arthritis patients.

The study used specialized isokinetic dynamometry which is mostly used in hospital and highly specialized settings. However, grip strength, wrist flexor and extensor strength can be easily measured using a hand-held dynamometer. Instead of measuring isokinetic strength, we only measure isometric strength, but still having this objective measurement is better than making a guess. For wrist supination and pronation, isometric handheld dynamometry is not valid compared to the isokinetic measurement (Bonhof-Jansen et al. 2023) but for wrist flexion and extension, Lucado et al. (2019) showed that correlations were moderate to high.

Joint position error assessment was also obtained using an isokinetic device. Yet, the measurement could be obtained by designing a measurement for the wrist using a laser pointer and a target, like we demonstrated for the shoulder in the following video.

Take-home messages

This study examined sensorimotor wrist function in rheumatoid arthritis patients and revealed significant deficits in both the dominant and non-dominant wrists when compared to healthy controls. Joint position sense, grip strength, and strength of the extensors and flexor muscles were all affected. This was correlated to pain and disability on the Patient Rated Wrist Evaluation Questionnaire, implying that these variables of sensorimotor function were related to worse ADL outcomes. It is crucial to evaluate the sensorimotor function of the wrist in patients with rheumatoid arthritis and to implement improving it in people affected. Finally, sensorimotor examinations should be included in routine rheumatoid arthritis evaluations in clinical practice. The findings support the use of focused wrist exercises in physiotherapy programs to increase both strength and proprioception in rheumatoid arthritis patients, resulting in superior functional outcomes.

Reference

Tore NG, Zorlular A, Yildirim D, Atalay Guzel N, Oskay D. Investigation of sensory and motor functions of wrist in patients with rheumatoid arthritis. Musculoskelet Sci Pract. 2024 Aug;72:103122. doi: 10.1016/j.msksp.2024.103122. Epub 2024 Jun 12. PMID: 38909501.