Dr. David J. Bozentka answers your questions about MP joint arthritis.
What is the MP joint?
The metacarpophalangeal (MP) joint is the large knuckle joint located where the fingers and thumb meet the hand (Figure 1). The metacarpal bones lie within the palm and the phalanges lie within the digits. The metacarpal head, or ball part of the MP joint, meets with the proximal phalanx which makes up the socket part of the joint. The bones on each side of the joint have a cartilage surface that allows smooth gliding. Multiple tendons cross this joint. Flexor tendons and small additional tendons in the hand promote flexion, or bending. The extensor tendons promote extension, or straightening, of the joint. A collateral ligament on each side of the joint provides stability for a pinching motion. The bones, ligaments, and tendons of the MP joint allow motion and stability for optimal hand function.
What causes MP arthritis?
Arthritis of the MP joint may develop in a similar manner as other joints of the body. In general, arthritis is categorized in two main groups: inflammatory arthritis and osteoarthritis, both of which may develop in the MP joint. Rheumatoid arthritis is an example of an inflammatory arthritis that commonly affects the MP joint. The inflammatory changes may lead to stretching of the ligaments, movement of the tendons from their regular location, and erosions of the joint. In contrast, osteoarthritis, also called degenerative arthritis, will more often affect the interphalangeal joints (the two joints within the fingers) and will tend to lead to less deformity of the MP than an inflammatory arthritis (Figure 2). Post traumatic arthritis, a form of osteoarthritis, develops associated with an injury.
What are the symptoms of MP arthritis?
A person with MP arthritis may notice pain, swelling, and stiffness of the affected joints. The pain often occurs during activities. As the process progresses, the pain may also occur at rest and at night. A person may notice stiffness in the joint and difficulty fully bending and straightening the joint. Swelling of the joint is often noted. Someone with rheumatoid arthritis of the joint may develop a deformity of the joint due to weakening of the supportive soft tissues and movement of the tendons from their normal location. People with an inflammatory arthritis may notice a localized swelling due to inflammation of the joint lining; this is called synovitis.
How will a doctor evaluate my MP joint?
A doctor will ask you about your symptoms and how they affect your activities. An evaluation of your hands and other joints will be performed. The localized area of tenderness, range of motion, and stability of the joints will be assessed. An x-ray may be taken to evaluate the extent of the arthritis. The physician will rule out other causes for pain in this region including tendonitis or nerve compression syndromes. Blood studies and a consultation by a rheumatologist may be required to make the diagnosis of an inflammatory arthritis. It is important to distinguish between osteoarthritis and an inflammatory arthritis as the treatment options differ.
How is MP joint arthritis treated?
The goal in treating MP arthritis is to decrease pain and improve function. People with rheumatoid arthritis and other types of inflammatory arthritis often benefit from an evaluation and treatment by a rheumatologist. The treatment of osteoarthritis will be dependent on the extent of a person’s symptoms. Frequently, treatment is not required if there is no pain or functional problems despite evidence of osteoarthritis on exam or x-ray. People with symptoms have multiple treatment options. A splint and treatments such as a hot wax bath may be helpful to limit pain. Medications, topical creams, and corticosteroid injections can provide temporary relief. If a trial of non-operative methods has not alleviated symptoms, a doctor may recommend surgery. The optimal surgical procedure for the MP joints will depend on the type of arthritis, severity, and functional needs of the patient. Severe arthritis of the thumb MP joint will often be treated with a fusion in which the bones are melded together. The loss of motion of the thumb MP joint that results from fusion does not typically cause significant functional problems; however, all attempts are made to maintain motion of the finger MP joints. A person with rheumatoid arthritis may be a candidate for a soft tissue procedure in which the inflamed joint lining is removed (synovectomy) and the extensor tendons are realigned. A joint replacement is considered for more severe stages of an inflammatory and osteoarthritis of the finger MP joints (Figure 3).
David J. Bozentka, MD, is the chief of Hand Surgery in the department of Orthopaedics at the Perelman School of Medicine at the University of Pennsylvania, and the chief of Orthopaedic Surgery at Penn Presbyterian Medical Center. Bozentka is Board-certified in Orthopaedic Surgery and has a Certificate of added Qualification in hand surgery. He specializes in the diagnosis and treatment of all conditions affecting the hand, wrist and elbow in patients of all ages. His research interests focus predominantly on distal radius fractures and trauma of the upper extremity.