Capsulitis is an inflammatory condition that affects the outer lining of the joint called the joint capsule. Capsulitis can occur at any joint in the human body. In the foot, capsulitis is commonly found in the forefoot beneath the ball-of-the-foot. The most common site where capsulitis occurs is beneath the second metatarsal head. Capsulitis of the forefoot is caused by excessive mechanical load being applied to the forefoot. Capsulitis is found equally in men and women. Capsulitis is most common in ages 30-60 years.
The joint capsule is the envelope that surrounds the joint. The inner lining of the capsule is called synovium. The synovium produces synovial fluid, the fluid that lubricates the joint. Capsulitis is an inflammatory condition of the synovium.
In this picture (right), the plantar aspect of each of the metatarsal heads is marked and numbered. The red area adjacent to the second metatarsal head is the most common area where capsulitis occurs in the forefoot.
Causes and contributing factors
The development of capsulitis in the forefoot is very dependant upon the relative length of each metatarsal bone. The longer the metatarsal bone, the greater the load that is applied to that bone and the greater the tendency for capsulitis to occur. In the picture to your left, the horizontal yellow lines define the relative length of the first, second and third metatarsal bones of the left foot. This picture shows how much longer the second metatarsal bone is. Why is this important? Let's use an example to describe why: take two bamboo poles, one five foot long and another ten feet long. Hook them under your arms and hold them out in front of you parallel to the ground. Now slowly lower the poles. The longer of the two poles, the ten-foot pole, is going to hit the ground first, followed by the shorter five-foot pole. This is essentially how the long metatarsal bones of the forefoot carry our body weight. With each and every step, this load is repeated. Ideally, we'd like to see that load applied to the foot is applied in such a way that it is equally distributed. Equal, even distribution of load helps to prevent focal loading on any one bone or soft tissue structure, but we'll often see that the bone behind the second toe, called the second metatarsal, is long, just like the ten-foot bamboo pole. Repetitive loading of the second metatarsal results in capsulitis of the second metatarsal phalangeal joint.
Over time, the metatarsal that is sustaining increased load will have one of two outcomes. The most common outcome is that the metatarsal will gradually increase its ability to carry load. The metatarsal bone will visibly change in size, becoming larger on x-ray. The image (left) shows red markings that define the girth of the second and third metatarsals. In this x-ray view, the second and third metatarsals should be approximately the same girth. You can see in the image how the second metatarsal is not only longer (yellow lines) but also larger, (red lines.) This particular image shows how a metatarsal, when subjected to increased load, will increase in size to accommodate that load. Alternatively, if the load applied to the metatarsal is significantly and rapidly increased, the metatarsal may sustain a stress fracture. A stress fracture is the method by which the metatarsal accommodates the load by changing the structure of the bone.
The primary goal in treating forefoot capsulitis is to find ways to off-load or redistribute load applied to the forefoot. Off-loading is a simple technique that can be accomplished in many different ways. Metatarsal pads and forefoot gel cushions are by far the most popular ways to off-load the forefoot. Proper placement of metatarsal pads can be a little tricky at first. We often recommend over-the-counter inserts with metatarsal pads as a reference for patients trying to place metatarsal pads in shoes. The advantage of the insert is that these particular inserts have the met pad positioned in the correct location in relationship to the metatarsal heads. Simply place the insert in the shoe and the metatarsal pad is properly placed. Once you know how a metatarsal pad should feel, you can use individual felt or foam metatarsal pads much more accurately.
Shoe design can also be used to off-load the forefoot and relieve symptoms of capsulitis. One example of a shoe that can aid in the treatment of capsulitis would be a clog. The rocker sole on a clog has been used for years to off-load the forefoot. Other examples of shoe modifications used to off-load the forefoot include a metatarsal bar and an anterior rocker sole.
Prescription orthotics are another method used to off-load the forefoot. Special modifications such as cut-outs or metatarsal pads can be built into orthotics to accommodate areas of capsulitis.
Should the conservative methods described for off-loading fail to relieve the pain, an injection of cortisone may be indicated to reduce capsular inflammation. It's important to realize that forefoot capsulitis is a mechanical problem caused by focal loading on one metatarsal head. Logic says that off-loading is necessary to decrease load applied to the metatarsal head. Cortisone may temporarily relieve pain from inflammation but will not change the mechanical factors that contribute to capsulitis.
Surgical procedures may help in recalcitrant cases of forefoot capsulitis. In particular, a metatarsal osteotomy is used to elevate the metatarsal and reduce the symptoms of capsulitis. An osteotomy is a surgical fracture in the metatarsal.
The following images show the steps used to complete a Jacoby osteotomy of the second metatarsal. Variations of this procedure may include the type of osteotomy or methods of fixation. Image 1 shows the location of the metatarsal head and planned incision. Image 2 shows the dissection of the extensor tendons and capsule of the second metatarsal phalangeal joint. Images 3 and 4 show isolation of the second metatarsal in preparation for the osteotomy. Images 5 and 6 show the V-shapedd osteotomy completed and ready for fixation. Image 7 shows final closure of the surgical wound.
This procedure is completed in a hospital or surgery center using a general anesthetic or local anesthetic with sedation. The procedure takes approximately 30 minutes to complete. Patients may be partial to full weight bearing following this surgery. Most patient will require some form of walking cast to protect the osteotomy during healing. Percutaneous K wire fixation, if used, is removed at three weeks. Most patients are back to 100% of full activities by 12 weeks post-op. Long-term success of a Jacoby osteotomy is good to excellent. Complications of this procedure include transfer lesions. A transfer lesion is capsulitis that occurs at a metatarsal head adjacent to the site of surgery. Transfer lesions are the result of excessive elevation of the metatarsal post-Jacoby osteotomy.
When to contact your doctor
Symptoms of capsulitis that fail to respond to conservative care within a period of several weeks should be evaluated by your podiatrist, orthopedist or family doctor.
References are pending.
Author(s) and date
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Cite this article as: Oster, Jeffrey. Capsulitis. http://www.myfootshop.com/article/capsulitis
Most recent article update: March 8th, 2018.
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