Diagnosis is mostly clinical and radiological. Technetium skeletal scintigrams are occasionally used to determine number of exostoses.

Some parents of children with MHE have observed autism-like social problems in their children. To explore those observations more deeply, a 2012 study by the Sanford-Burnham Medical Research Institute used a mouse model of MHE to observe cognitive function. The findings indicated that the mutant mice endorsed three autistic characteristics: social impairment, impairments in ultrasonic vocalization, and repetitive behavior.

Osteochondromas are often asymptomatic and may not cause any kind of discomfort. They are often found accidentally when an X-ray is done for an unrelated reason.

- X-rays are the first tests performed that characterize a lesion. They show a clear picture of dense structures of bones, and will also indicate bone growth pertaining to osteochondroma.

- Computed Tomography (CT) scan can identify the bony lesion in great details and show the presence of calcification. These tests also provide great details, especially in soft tissues with the aide of cross-sectional images.

- Magnetic Resonance Imaging (MRI) is the most accurate method for detecting bone masses in symptomatic cases to depict precise morphology of a tumor. It is used to verify if the palpable mass is continuous with the cortex of the affected bone and to differentiate an osteochondroma from other lesions on the surface of the bone. MRI can also be used to look for cartilage on the surface of tumor and can depict any vascular complications caused by the tumor. An MRI can identify tumors of the spinal column and is often used to diagnose low grade osteosarcoma.

- Ultrasound is done if aneurysms or pseudoaneurysms and venous or arterial thrombosis is suspected. Ultrasound is an accurate method for examining the cartilaginous cap of the osteochondroma. It is also a way of pinpointing bursitis. However, it cannot be used to predict if the growth of tumor is inward in regards to the cap.

- Angiography is used to detect vascular lesions caused by osteochondroma due to ossified cartilaginous cap. It is also used to characterize malignant transformation lesions through neovascularity.

- Clinical testing such as sequence analysis can be done of the entire coding regions of both "EXT1" and "EXT2" to detect mutations.

- A biopsy of the tissue sample of the tumor can also be taken to check for cancer.

Tests for osteochondroma can also identify diseases such as secondary peripheral chondrosarcoma and Multiple osteochondromatosis. In large, secondary chondrosarcoma arises at the site of osteochondroma due to increased thickness of the cartilage cap indicating potential malignant transformation. The symptoms of multiple osteochondromatosis are similar to solitary osteochondroma, but they are often more severe. Painless bumps can arise at the site of tumor and pain and other discomforts can also take place if pressure is put on the soft tissues, nerves, or blood vessels. Dysplasia Epiphysealis Hemimelica (DEH) or Trevor's disease and metachondromatosis (MC) are considered differential diagnosis of both solitary and hereditary osteochondromas. DEH is described as a type of over growth at one or more epiphyses. Similar to osteochondroma, DEH is diagnosed prior to 15 years of age and the growth of lesions end at puberty, when the growth plates close. Metachondromatosis is a rare disorder that exhibit symptoms of both multiple osteochondromas and enchondromas in children and is also inherited in autosomal dominant mode.

Osteochondromas are benign lesions and do not affect life expectancy. Complete excision of osteochondroma is curative and the reoccurrences take place when the removal of tumor is incomplete. Multiple reoccurrences in a well-excised lesion indicate that it may be malignant. The risk of malignant transformation takes place in 1–5% of individuals. If any symptoms of cancerous tumor takes place, then the patient should be evaluated by a bone specialist. No treatment is necessary for Solitary osteochondromas that are asymptomatic. Treatments for solitary osteochondroma are careful observation over time and taking regular x-rays to monitor any changes in the tumor. If the lesion is causing pain with activity, nerve or vessel impingement, or if the bone growth has fully matured and the presence of a large cartilage cap is prominent, then it is advised that the tumor be surgically removed.

Osteochondromas have a low rate of malignancy (<1%) and resection of the tumor is suggested if symptoms such as pain, limitation of movement, or impingement on nerves or vessels occur. Resection of the tumor also takes place when the tumor increases in size and progresses towards malignancy. During surgical resection, the entire lesion along with the cartilaginous cap should be removed to minimize any chances of reoccurrences. Surgical treatment becomes the sole treatment of choice if common complications such as fractures, symptoms of peripheral nerves such as paresthesia, paraplegia, peroneal neuropathy, and upper limb neuropathy take place. A prophylactic resection is suggested if the lesion lies next to a vessel.

Depending on the size and location of the tumor, the time it takes to return to normal daily activities varies between individuals. Limitation on some activities is advised if pain or discomfort persists after surgical excision.

Osteochondromatosis is a condition involving a proliferation of osteochondromas.

Types include:

- Hereditary multiple exostoses

- Synovial osteochondromatosis

Treatment is frequently by means of removal of the loose bodies and of a partial or full synovectomy (removal of the synovium)

Full synovectomy is a moderately major operation and involves completely exposing the joint and removing the affected tissue. Partial synovectomy is normally done arthroscopically. Synovectomies are normally carried out by shaving the lining of the knee but there are other ways of achieving this by either freezing the synovium or by the use of radiation treatment.

The need for further procedures is greater than 25% although normally the frequency of the required removal of loose bodies is reduced by the previous synovectomy. There have been documented cases of malignant transformation however this is rare.

Whilst the condition can be described as a ‘benign growth’ it seldom affects more than one joint, and does not usually affect surrounding tissue.

Patients usually complain of pain in one joint, which persists for months, or even years, does not ease with exercise, steroid injection or heat treatment, shows nothing on X-ray, but shows a definite restriction of movement.

There are 3 defined stages to this disease:

- early: no loose bodies but active synovial disease;

- transitional: active synovial disease, and loose bodies;

- late: loose bodies but no synovial disease;

In the early stages of the disease it is often confused with tendinitis and/or arthritis. Once it reaches transitional the loose bodies become apparent with X-ray in greater than 70% of cases, with MRI often showing where xray fails. In experienced hands, US is also useful for the diagnosis.

In the disease, the thin flexible membrane of the synovium gradually forms blisters which calcify and enlarge. These nodules eventually break free and float around the joint space becoming larger – these add to the discomfort and stiffness of the joint.

The disease is rare and little known and there is currently no known cure. The affected tissue will show up as a semi-solid mass in a MRI scan, final diagnosis is usually confirmed by taking a biopsy.

Synovial chondromatosis occurs twice as commonly in males as females and usually in their forties. However, online communities for synovial chondromatosis patients have yielded a stark contrast, with equal representation from both genders and members diagnosed as young as late teenage/early 20s.

The disease generally affects only one of the larger weight bearing joints (hip, ankle, knee) – although the elbow, and wrist can also be affected. Rarely involves the temporal mandibular joint.

A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of multiple independent primary tumors. Many of these syndromes are caused by mutations in tumor suppressor genes, genes that are involved in protecting the cell from turning cancerous. Other genes that may be affected are DNA repair genes, oncogenes and genes involved in the production of blood vessels (angiogenesis). Common examples of inherited cancer syndromes are hereditary breast-ovarian cancer syndrome and hereditary non-polyposis colon cancer (Lynch syndrome).

Hereditary cancer syndromes underlie 5 to 10% of all cancers. Scientific understanding of cancer susceptibility syndromes is actively expanding: additional syndromes are being found, the underlying biology is becoming clearer, and commercialization of diagnostic genetics methodology is improving clinical access. Given the prevalence of breast and colon cancer, the most widely recognized syndromes include hereditary breast-ovarian cancer syndrome (HBOC) and hereditary non-polyposis colon cancer (HNPCC, Lynch syndrome).

Some rare cancers are strongly associated with hereditary cancer predisposition syndromes. Genetic testing should be considered with adrenocortical carcinoma; carcinoid tumors; diffuse gastric cancer; fallopian tube/primary peritoneal cancer; leiomyosarcoma; medullary thyroid cancer; paraganglioma/pheochromocytoma; renal cell carcinoma of chromophobe, hybrid oncocytic, or oncocytoma histology; sebaceous carcinoma; and sex cord tumors with annular tubules. Primary care physicians can identify people who are at risk of heridatary cancer syndrome.