# Bump on Your Dog's Leg or Foot: Causes and When to Worry A dog bump on the leg is a lump or swelling anywhere from the shoulder down to the toes, and most turn out to be harmless fatty growths or cysts. Some, though, are tumors that need prompt care. The location, how fast it grew, and whether your dog is limping all help point to the answer. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Most leg bumps in dogs are benign lipomas (soft fat lumps) or cysts, but you cannot tell by feel alone. - A bump that appeared suddenly after a fall, jump, or rough play is often a bruise or swelling, not a tumor. - Fast growth, firmness, pain, redness, or limping raises concern and needs a vet visit soon. - Any open, bleeding, or draining lump on the foot or leg should be seen the same day. - Your vet can often identify the lump with a simple needle sample in the exam room, no surgery needed. ## What a Leg or Foot Bump Looks Like and What Is Normal Dogs get lumps. Middle-aged and older dogs often develop several soft, movable bumps under the skin, and many of these are harmless. A normal, low-concern bump is usually soft, round, movable under the skin, and slow growing. It does not hurt when you touch it, and the skin over it looks normal. Bumps on the leg and foot are a little different from bumps on the torso. The legs have less loose skin and less padding, so even a small mass can press on bone, tendon, or joint. That is one reason a leg lump may cause limping sooner than a lump on the chest or flank. You may notice the bump while petting your dog, trimming nails, or drying paws after a walk. Some owners find a lump on the thigh or knee during a bath. Others spot a swelling on the foot when the dog starts licking one toe. It helps to note a few things right away. Take a photo with a ruler or coin next to the lump for scale. Write down the date. Check whether the lump is on the skin surface, just under the skin, or deep against the bone. These details help your vet decide how urgent it is. ## Main Causes of a Dog Bump on the Leg Causes range from harmless to serious. The table below groups the most common ones and what makes each stand out. | Cause | Typical clues | How urgent | |---|---|---| | Lipoma (benign fat tumor) | Soft, squishy, movable, slow growing, usually not painful | Routine visit | | Sebaceous cyst or follicular cyst | Round, attached to skin, may have a pore or discharge cheesy material | Routine visit | | Abscess or infected wound | Warm, painful, red, may drain pus, often after a cut or bite | Same day | | Bruise or soft tissue swelling | Appears after trauma, may be warm and tender, improves over days | Same day if limping badly | | Insect bite or sting | Sudden swelling, itching, sometimes hives elsewhere | Same day if face or breathing involved | | Foreign body (foxtail, splinter, glass) | Small wound or swelling between toes, licking, limping | Same day | | Mast cell tumor | Often raised, hairless, may change size after touching, can be itchy | Soon, within days | | Soft tissue sarcoma | Firm, deep, often on a limb, may invade bone over time | Soon, within days | | Osteosarcoma (bone cancer) | Firm swelling near a joint, pain, lameness, often on a limb | Soon, within days | | Transmissible venereal tumor (TVT) | Round cell tumor, usually genital, can spread to other sites | Soon, within days | ### Lipomas and Cysts Lipomas are the most common benign soft tissue mass in dogs. They feel like a bag of soft jelly under the skin and usually move freely. Cysts are fluid or debris filled pockets that sit in or just under the skin. Both are usually harmless, but a fast growing or firm lump should still be checked. ### Tumors of the Leg and Bone Not every lump is benign. Soft tissue sarcomas are a common canine cancer that can arise on a limb and, in rare cases, invade the bone beneath it. One report described a soft tissue sarcoma that grew into the proximal humerus (the upper arm bone) through a small opening called the nutrient foramen, causing non-weight-bearing lameness in a dog [1]. That case shows how a leg mass can affect bone and walking. Bone cancer is another concern. Osteosarcoma is the most common primary bone tumor in dogs, though it rarely affects the pelvis. In a study of 74 dogs with pelvic osteosarcoma, lameness was the most common sign, seen in 84% of cases, and 31% already had metastases at diagnosis, mostly in the lungs [2]. This is why a firm, painful leg swelling with limping needs prompt imaging. Round cell tumors can also appear as leg lumps. Canine transmissible venereal tumor (TVT) usually affects the genital area, but extragenital and metastatic forms do occur and can be hard to diagnose when genital lesions are absent [3]. These tumors are treatable, so identifying them matters. ### Bumps Caused by Injury or Infection Many sudden bumps are not tumors at all. A dog that lands hard after a jump can develop a bruise or fluid pocket on the leg. A small cut between the toes can become an abscess. A grass awn or splinter can work into the foot and cause a firm, painful swelling. These often improve with wound care and antibiotics, but they can look alarming at first. ## Red Flags That Make It an Emergency Some signs mean you should stop watching and go now. - The leg is swollen, hot, and your dog will not put weight on it. - The lump is bleeding, oozing, or has an open wound that will not stop. - Your dog is panting, weak, pale, or collapsing. - The foot or leg is suddenly very large, tight, or discolored. - Your dog cried out or pulled away when the area was touched. - The lump appeared overnight and is growing by the hour. - Your dog has trouble breathing along with the leg swelling. Weakness in the back legs can also come from problems far from the leg, such as a liver mass causing low blood sugar. One report described a dog with recurrent hind limb weakness and collapse from severe hypoglycemia tied to a liver tumor, with blood glucose as low as 26 mg/dL [4]. If your dog has episodes of weakness or collapse along with a lump, treat it as urgent. ## Safe Things You Can Do at Home While Waiting You can gather information and keep your dog comfortable without trying to treat the lump yourself. - Do not squeeze, poke, or try to pop the lump. This can spread infection or irritate a tumor. - Take clear photos from two angles with a ruler or coin for scale. - Measure the lump with a soft tape or a piece of string, and write down the number. - Check the lump daily and note any change in size, color, or firmness. - Keep your dog from licking or chewing the area. A cone or soft collar can help. - Limit running, jumping, and stairs if your dog is limping. - Use a cold pack wrapped in a towel for 10 minutes at a time if the area is swollen from a recent injury. - Do not give any human pain medicine. Many are toxic to dogs, and the dose depends on your dog's weight and health. Your vet will calculate the right dose. If your dog is limping, our guide on [why is my dog limping on the front leg](/knowledge/veterinary-medicine/symptom-guides/dog-limping-front-leg) can help you sort out what to watch for. If the limping comes and goes, see [dog limping front leg sometimes](/knowledge/veterinary-medicine/symptom-guides/dog-limping-front-leg-sometimes). ## What Your Veterinarian Will Check and Test Your vet will start with a physical exam. They will feel the lump, check its size, depth, and how movable it is. They will also watch your dog walk and check the joints above and below the lump. Next, they often do a fine needle aspirate. This is a quick, low-pain test where a thin needle collects cells from the lump. The cells are examined under a microscope. This can often tell a lipoma from a cyst or a tumor in minutes. If the aspirate is unclear, your vet may recommend a biopsy. A biopsy removes a small piece of tissue for lab analysis. This gives a definitive diagnosis and helps guide treatment. Imaging may be needed. X-rays can show whether a mass is affecting the bone. In the soft tissue sarcoma case, X-rays showed a region of bone destruction in the upper arm bone, which helped guide surgery [1]. For bone tumors, X-rays and sometimes CT scans help stage the disease. In the pelvic osteosarcoma study, 31% of dogs had metastases at diagnosis, so chest imaging is often part of the workup [2]. Blood work may be recommended, especially if your dog is weak or not eating. It can check for anemia, infection, and organ function. In some cases, blood sugar testing is important, as with the dog that had severe hypoglycemia from a liver mass [4]. Treatment depends on the diagnosis. Benign lumps may need no treatment or simple removal. Infected lumps need drainage and antibiotics. Tumors may need surgery, and sometimes chemotherapy or radiation. In the soft tissue sarcoma case, amputation was performed, and the dog recovered well and maintained a good quality of life for 15 months after surgery [1]. ## Prevention and Monitoring You cannot prevent every lump, but you can catch problems early. - Do a monthly lump check. Run your hands over your dog's legs, feet, and body while they are relaxed. - Keep a simple log with dates, sizes, and photos. - Schedule a vet visit for any new lump that is firm, fast growing, or painful. - Keep your dog at a healthy weight. Extra weight puts more stress on joints and legs. - Trim the hair between the toes and check paws after walks in tall grass. - Use paw protection in hot or rough terrain. - Ask your vet to check any lump that changes between visits. Early detection gives you more options. Many leg tumors are easier to treat when they are small and have not spread. ## Limitations and When to Contact a Veterinarian No article can tell you what your dog's lump is. Only a veterinarian who examines your dog and runs tests can do that. Individual cases need a veterinarian. Contact your vet the same day if the lump is new, firm, painful, or your dog is limping. Go to an emergency clinic now if your dog cannot bear weight, is bleeding heavily, is panting or weak, or has trouble breathing. Schedule a routine visit if the lump is soft, slow growing, and your dog is acting normal. If you are unsure, call your vet's office and describe what you see. They can tell you whether to come in now or wait. ## Frequently Asked Questions ### Is a bump on my dog's leg always cancer? No, most leg bumps are not cancer. Lipomas, cysts, and injury-related swelling are far more common. Still, you cannot tell by feel alone, so a vet exam is the safe choice. ### Can I wait a few weeks to see if the bump goes away? You can wait a few days for a soft lump that appeared after a minor injury, but not for a firm, fast growing, or painful one. If it is still there after a week, or if it changes at all, book a visit. ### Does limping mean the bump is serious? Limping means the lump or the leg is causing pain or affecting how your dog walks. That can happen with a bruise, an infection, or a tumor. Any limp that lasts more than a day or two needs a vet check. ### Will my vet remove the lump right away? Not always. If the lump is a harmless lipoma or cyst, your vet may just monitor it. If it is a tumor or an infection, removal or other treatment may be recommended. The plan depends on the diagnosis. ### Can a leg lump spread to other parts of my dog's body? Some tumors can spread, especially bone cancer and certain round cell tumors. In the pelvic osteosarcoma study, 31% of dogs already had metastases at diagnosis [2]. That is why early testing and staging matter. ## Related Articles - [Why Is My Dog Limping On The Front Leg](/knowledge/veterinary-medicine/symptom-guides/dog-limping-front-leg) - [Why Is My Dog Limping On Front Leg](/knowledge/veterinary-medicine/symptom-guides/dog-limping-front-leg) - [Why's My Dog Limping On His Front Leg](/knowledge/veterinary-medicine/symptom-guides/why-s-my-dog-limping-on-his-front-leg) - [Dog Limping Front Leg Sometimes](/knowledge/veterinary-medicine/symptom-guides/dog-limping-front-leg-sometimes) - [Why Is My Dog Limping On Her Front Leg](/knowledge/veterinary-medicine/symptom-guides/why-is-my-dog-limping-on-her-front-leg) - [Dog Front Leg Clicking And Limping](/knowledge/veterinary-medicine/symptom-guides/dog-front-leg-clicking-and-limping) - [Growth on Your Dog's Leg or Foot: When to Get It Checked](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-growth-on-leg-foot) - [Lump on Your Dog's Leg, Knee, or Ankle](/knowledge/veterinary-medicine/symptom-guides/dog-leg-knee-lump) - [Bump Between Your Dog's Toes: Causes and When to Worry](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-bump-between-toes) ## References 1. [Soft tissue sarcoma invasion of the humerus via the nutrient foramen in a dog](https://pubmed.ncbi.nlm.nih.gov/42699814/). The Canadian veterinary journal = La revue veterinaire canadienne, 2026. 2. [Clinical Behaviour and Outcome of Pelvic Osteosarcoma in Dogs: A Retrospective Multicentre Analysis of 74 Cases (2007-2025)](https://pubmed.ncbi.nlm.nih.gov/42630097/). Veterinary and comparative oncology, 2026. 3. [Diagnostic challenge of pulmonary metastatic transmissible venereal tumour in a young dog](https://pubmed.ncbi.nlm.nih.gov/42019465/). Journal of comparative pathology, 2026. 4. [Resolution of Recurrent Severe Hypoglycemia After Surgical Excision of a Primary Hepatic Neoplasm of Uncertain Histogenesis in a Dog: A Case Report](https://pubmed.ncbi.nlm.nih.gov/42655842/). Veterinary sciences, 2026. ## Further Reading - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)